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Tomohiro Otsuka

Section

Advanced Institute for Materials Research

Job title

Associate Professor

Degree

Doctor of Science (University of Tokyo)

researchmap

https://researchmap.jp/t-otsuka

J-GLOBAL ID

201101087973149169

e-Rad No.

50588019

Research History 20

2025/05 - Present

National Institute for Materials Science　Research Center for Materials Nanoarchitechtonics　Chief Invited Researcher
2024/04 - Present

Tohoku University　Research Center for Neutrino Science　Associate Professor
2022/04 - Present

Tohoku University　Advanced Institute for Materials Research　Associate Professor
2020/08 - Present

Tohoku University　Tohoku Quantum Alliance　Co-director
2019/12 - Present

Organization for Advanced Studies　Associate Professor
2019/04 - Present

Center for Science and Innovation in Spintronics, Tohoku University　Associate Professor
2018/04 - Present

Department of Electrical Engineering, School of Engineering, Tohoku University　Associate Professor
2018/02 - Present

Research Institute of Electrical Communication, Tohoku University (Quantum Devices (Otsuka Group), Information Devices Division)　Associate Professor
2018/02 - Present

RIKEN (Center for Emergent Matter Science, Quantum Functional System Research Group)　Visiting Researcher
2018/04 - 2022/03

Center for Spintronics Research Network, Tohoku University　Associate Professor
2018/02 - 2022/03

Leading Initiative for Excellent Young Researchers, MEXT-Japan
2016/10 - 2020/03

JST, PRESTO　Project Researcher
2013/04 - 2020/03

Department of Applied Physics, University of Tokyo (Tarucha-Yamamoto Lab)　Visiting Researcher
2016/01 - 2018/01

RIKEN (Center for Emergent Matter Science, Quantum Functional System Research Group)　Research Scientist
2013/04 - 2015/12

RIKEN (Quantum Functional System Research Group, Center for Emergent Matter Science)　Postdoctoral Researcher
2012/09 - 2013/03

RIKEN (Emergent Quantum Function Research Team, Functional Emergent-matter Research Group, Emergent Materials Department, Advanced Science Institute)　Visiting Researcher
2010/04 - 2013/03

Department of Applied Physics, University of Tokyo (Tarucha-Oiwa Lab)　Project Researcher
2012/10 - 2013/02

IARPA Exchange Program (Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen)
2007/04 - 2010/03

the Japan Society for the Promotion of Science　Research Fellow (DC)
2006/10 - 2007/03

Institute for Solid State Physics, University of Tokyo (Katsumoto Lab)　Technical Assistant

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Education 3

University of Tokyo (ISSP Katsumoto Lab)　Ph.D. course, Department of Physics

2007/04 - 2010/03
University of Tokyo (ISSP Katsumoto Lab)　Master course, Department of Physics

2005/04 - 2007/03
University of Tokyo　Department of Physics

2003/04 - 2005/03

Professional Memberships 1

THE PHYSICAL SOCIETY OF JAPAN

Research Interests 12

Mesoscopic system
Semiconductor
Quantum computer
Quantum bit
Spintronics
Quantum Device
Quantum Wire
Quantum Dot
Semiconductor Physics
Low Temperature Physics
Condensed Matter Physics
量子情報処理プロジェクト

Research Areas 3

Natural sciences / Semiconductors, optical and atomic physics /
Nanotechnology/Materials / Nano/micro-systems /
Nanotechnology/Materials / Nanomaterials /

Awards 13

Minoru Ishida Foundation Research Award

2025/11　Minoru Ishida Foundation
Distinguished Researcher

2023/04　Tohoku University
Distinguished Researcher

2020/07　Tohoku University
Intelligent Cosmos Academic Foundation Research Encouraging Award

2020/05　Intelligent Cosmos Academic Foundation
RIEC Research Exchange Meeting Good Presentation Award

2018/09　RIEC, Tohoku University
The Young Scientists’ Prize, The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology

2018/04　Minister of Education, Culture, Sports, Science and Technology
Yazaki Memorial Foundation for Science and Technology Research Encouraging Award

2018/03　Yazaki Memorial Foundation
Foundation Advanced Technology Institute Research Encouraging Award

2017/05　Foundation Advanced Technology Institute
RIKEN CEMS Award

2017/04　CEMS, RIKEN
Young Scientist Award of the Physical Society of Japan

2017/03　the Physical Society of Japan
RIKEN Researcher Incentive Award

2017/03　RIKEN
NF Foundation R&D Encouragement Award

2014/11　NF Foundation
Research Encouraging Prize, School of Science, University of Tokyo

2010/03　School of Science, University of Tokyo

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Papers 81

Automatic detection of single-electron regime and virtual gate definition in quantum dots using U-Net and clustering Peer-reviewed

Yui Muto, Michael R. Zielewski, Motoya Shinozaki, Kosuke Noro, Tomohiro Otsuka

Scientific Reports　16　8161　2026/02/14
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41598-026-38889-7 　

eISSN： 2045-2322

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Abstract To realize practical quantum computers, a large number of quantum bits (qubits) will be required. Semiconductor spin qubits offer advantages such as high scalability and compatibility with existing semiconductor technologies. However, as the number of qubits increases, manual qubit tuning becomes infeasible, motivating automated tuning approaches. In this study, we use U-Net, a neural network method for object detection, to identify charge transition lines in experimental charge stability diagrams. The extracted charge transition lines are analyzed using the Hough transform to determine their positions and angles. Based on this analysis, we obtain the transformation matrix to virtual gates. Furthermore, we identify the single-electron regime by clustering the Hough transform outputs. We also show the single-electron regime within the virtual gate space. These sequential processes are performed automatically. This approach will advance automated control technologies for large-scale quantum devices.
Magnetotransport and Coulomb Blockade in Single InAs Colloidal Quantum Dot Transistors Peer-reviewed

Kenji Shibata, Tomoki Takiguchi, Akira Sato, Yuto Sasaki, Tomohiro Otsuka

ACS Nano　20　2082　2026/01/04

DOI： 10.1021/acsnano.5c14784 　
ノーベル賞が照らす量子技術の広がり―観測する量子から，設計する量子へ―

大塚朋廣

応用物理　95　7　2026/01/01

DOI： 10.11470/oubutsu.95.1_7 　
Formation of few-electron triple quantum dots in ZnO heterostructures Peer-reviewed

Koichi Baba, Kosuke Noro, Yusuke Kozuka, Takeshi Kumasaka, Motoya Shinozaki, Masashi Kawasaki, Tomohiro Otsuka

Scientific Reports　15　(1)　36612　2025/10/21

DOI： 10.1038/s41598-025-20567-9 　

ISSN： 2045-2322
On-board calibrated radio-frequency measurement at cryogenic temperatures for determination of SrTiO3-based capacitor properties Peer-reviewed

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Hisashi Inoue, Kenta Itoh, Yusuke Kozuka, Takanobu Watanabe, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

Applied Physics Letters　127　153501　2025/10/13

DOI： 10.1063/5.0299758 　
RFSoC-based radio-frequency reflectometry in gate-defined bilayer graphene quantum devices Peer-reviewed

Motoya Shinozaki, Tomoya Johmen, Aruto Hosaka, Takumi Seo, Shunsuke Yashima, Akitomi Shirachi, Kosuke Noro, Shoichi Sato, Takashi Kumasaka, Tsuyoshi Yoshida, Tomohiro Otsuka

Applied Physics Express　18　(7)　075001-1-075001-5　2025/07/09

DOI： 10.35848/1882-0786/ade6c2 　
Charge-state estimation in quantum dots using a Bayesian approach Peer-reviewed

Motoya Shinozaki, Yui Muto, Takahito Kitada, Tomohiro Otsuka

Physical Review Applied　23　034078　2025/03/26

DOI： 10.1103/PhysRevApplied.23.034078 　
Lattice-guided growth of dense arrays of aligned transition metal dichalcogenide nanoribbons with high catalytic reactivity Peer-reviewed

Zongpeng Ma, Pablo Solís-Fernández, Kaito Hirata, Yung-Chang Lin, Keisuke Shinokita, Mina Maruyama, Kota Honda, Tatsuki Kato, Aika Uchida, Hiroto Ogura, Tomohiro Otsuka, Masahiro Hara, Kazunari Matsuda, Kazu Suenaga, Susumu Okada, Toshiaki Kato, Yasufumi Takahashi, Hiroki Ago

Science Advances　11　(2)　eadr8046　2025/01/08
Publisher: American Association for the Advancement of Science (AAAS)
DOI： 10.1126/sciadv.adr8046 　

eISSN： 2375-2548

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Transition metal dichalcogenides (TMDs) exhibit unique properties and potential applications when reduced to one-dimensional (1D) nanoribbons (NRs), owing to quantum confinement and high edge densities. However, effective growth methods for self-aligned TMD NRs are still lacking. We demonstrate a versatile approach for lattice-guided growth of dense, aligned MoS ₂ NR arrays via chemical vapor deposition (CVD) on anisotropic sapphire substrates, without tailored surface steps. This method enables the synthesis of NRs with widths below 10 nanometers and longitudinal axis parallel to the zigzag direction, being also extensible to the growth of WS ₂ NRs and MoS ₂ -WS ₂ heteronanoribbons. Growth is influenced by both substrate and CVD temperature, indicating the role of anisotropic precursor diffusion and substrate interaction. The 1D nature of the NRs was asserted by the observation of Coulomb blockade at low temperatures. Pronounced catalytic activity was observed at the edges of the NRs, indicating their promise for efficient catalysis.
Dynamics of quantum cellular automata electron transition in triple quantum dots Peer-reviewed

Takumi Aizawa, Motoya Shinozaki, Yoshihiro Fujiwara, Takeshi Kumasaka, Wataru Izumida, Arne Ludwig, Andreas D. Wieck, Tomohiro Otsuka

Physical Review B　110　235421　2024/12/18

DOI： 10.1103/PhysRevB.110.235421 　
Probing electron trapping by current collapse in GaN/AlGaN FETs utilizing quantum transport characteristics Peer-reviewed

Takaya Abe, Motoya Shinozaki, Kazuma Matsumura, Takumi Aizawa, Takeshi Kumasaka, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

Applied Physics Letters　125　253501　2024/12/16

DOI： 10.1063/5.0232463 　
Parity-independent Kondo effect of correlated electrons in electrostatically defined ZnO quantum dots Peer-reviewed

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

Nature Communications　15　9556　2024/11/07

DOI： 10.1038/s41467-024-53890-2 　

eISSN： 2041-1723
Surface Gate-Defined Quantum Dots in MoS₂ with Bi Contacts Peer-reviewed

Riku Tataka, Alka Sharma, Motoya Shinozaki, Tomoya Johmen, Takeshi Kumasaka, Yong P. Chen, Tomohiro Otsuka

Journal of the Physical Society of Japan　93　(9)　094601-1-094601-5　2024/09/15
Publisher: Physical Society of Japan
DOI： 10.7566/jpsj.93.094601 　

ISSN： 0031-9015

eISSN： 1347-4073
Microwave-dependent quantum transport characteristics in near pinched-off GaN/AlGaN field-effect transistors Peer-reviewed

Motoya Shinozaki, Takaya Abe, Kazuma Matsumura, Takumi Aizawa, Takeshi Kumasaka, Tomohiro Otsuka

Physical Review B　110　035305-1-035305-7　2024/07/17
Publisher: American Physical Society (APS)
DOI： 10.1103/physrevb.110.035305 　

ISSN： 2469-9950

eISSN： 2469-9969
Visual explanations of machine learning model estimating charge states in quantum dots Peer-reviewed

Yui Muto, Takumi Nakaso, Motoya Shinozaki, Takumi Aizawa, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

APL Machine Learning　2　026110-1-026110-7　2024/04/15
Publisher: AIP Publishing
DOI： 10.1063/5.0193621 　

eISSN： 2770-9019

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Charge state recognition in quantum dot devices is important in the preparation of quantum bits for quantum information processing. Toward auto-tuning of larger-scale quantum devices, automatic charge state recognition by machine learning has been demonstrated. For further development of this technology, an understanding of the operation of the machine learning model, which is usually a black box, will be useful. In this study, we analyze the explainability of the machine learning model estimating charge states in quantum dots by gradient weighted class activation mapping. This technique highlights the important regions in the image for predicting the class. The model predicts the state based on the change transition lines, indicating that human-like recognition is realized. We also demonstrate improvements of the model by utilizing feedback from the mapping results. Due to the simplicity of our simulation and pre-processing methods, our approach offers scalability without significant additional simulation costs, demonstrating its suitability for future quantum dot system expansions.
Wide dynamic range charge sensor operation by high-speed feedback control of radio-frequency reflectometry Peer-reviewed

Yoshihiro Fujiwara, Motoya Shinozaki, Kazuma Matsumura, Kosuke Noro, Riku Tataka, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

Applied Physics Letters　123　(21)　213502-1-213502-7　2023/11/20
Publisher: AIP Publishing
DOI： 10.1063/5.0167212 　

ISSN： 0003-6951

eISSN： 1077-3118

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Semiconductor quantum dots are useful for controlling and observing quantum states and can also be used as sensors for reading out quantum bits and exploring local electronic states in nanostructures. However, challenges remain for the sensor applications, such as the trade-off between sensitivity and dynamic range and the issue of instability due to external disturbances. In this study, we demonstrate proportional-integral-differential feedback control of the radio-frequency reflectometry in GaN nanodevices using a field-programmable gate array. This technique can maintain the operating point of the charge sensor with high sensitivity. The system also realizes a wide dynamic range and high sensor sensitivity through the monitoring of the feedback signal. This method has potential applications in exploring dynamics and instability of electronic and quantum states in nanostructures.
Single PbS colloidal quantum dot transistors Peer-reviewed

Kenji Shibata, Masaki Yoshida, Kazuhiko Hirakawa, Tomohiro Otsuka, Satria Zulkarnaen Bisri, Yoshihiro Iwasa

Nature Communications　14　7486-1-7486-8　2023/11/07

DOI： 10.1038/s41467-023-43343-7 　

eISSN： 2041-1723
Radio-Frequency Reflectometry in Bilayer Graphene Devices Utilizing Microscale Graphite Back-Gates Peer-reviewed

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Takumi Aizawa, Tomohiro Otsuka

Physical Review Applied　20　(1)　2023/07/17
Publisher: American Physical Society (APS)
DOI： 10.1103/physrevapplied.20.014035 　

eISSN： 2331-7019
Channel length dependence of the formation of quantum dots in GaN/AlGaN FETs Peer-reviewed

Kazuma Matsumura, Takaya Abe, Takahito Kitada, Takeshi Kumasaka, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

Applied Physics Express　16　(7)　075003-075003　2023/07/01
Publisher: IOP Publishing
DOI： 10.35848/1882-0786/ace415 　

ISSN： 1882-0778

eISSN： 1882-0786

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Abstract Quantum dots can be formed in simple GaN/AlGaN FETs by disordered potential induced by impurities and defects. Here, we investigate the channel length dependence of the formation of quantum dots. We observe a decrease in the number of formed quantum dots with a decrease in the FET channel length. A few quantum dots are formed in the case with a gate length of 0.05 μm and we evaluate the dot parameters and the disordered potential. We also investigate the effects of a thermal cycle and illumination of light and reveal the change of the disordered potential.
Nonlinear conductance in nanoscale CoFeB/MgO magnetic tunnel junctions with perpendicular easy axis Peer-reviewed

Motoya Shinozaki, Junta Igarashi, Shuichi Iwakiri, Takahito Kitada, Keisuke Hayakawa, Butsurin Jinnai, Tomohiro Otsuka, Shunsuke Fukami, Kensuke Kobayashi, Hideo Ohno

Physical Review B　2023/03/30

DOI： 10.1103/PhysRevB.107.094436 　
Scalable fabrication of graphene nanoribbon quantum dot devices with stable orbital-level spacing

Toshiaki Kato, Takahito Kitada, Mizuki Seo, Wakana Okita, Naofumi Sato, Motoya Shinozaki, Takaya Abe, Takeshi Kumasaka, Takumi Aizawa, Yui Muto, Toshiro Kaneko, Tomohiro Otsuka

Communications Materials　3　(1)　2022/12/22
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s43246-022-00326-3 　

eISSN： 2662-4443

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Abstract Large-scale integration of quantum-dot devices is essential for realizing various quantum devices. Graphene-based quantum dots provide a promising platform for spin qubits because of their low nuclear spin density and weak spin-orbit interaction. However, the integration of graphene-based quantum dots remains a challenge. Here, we demonstrate the scalable fabrication of graphene nanoribbon-based quantum-dot devices using a nickel nanobar technique. Fine structures formed in the middle of the nanoribbons exhibit quantum-dot behavior, and more than 56% of devices fabricated on the same substrate show Coulomb diamond features, indicating that large-scale integration of graphene nanoribbon quantum-dot devices is possible with our method. Cryogenic measurements reveal orbital-level spacings between the ground and excited states that are stable up to high-temperature conditions of ~20 K. We explain this stability in terms of the very fine structures formed in the middle of the nanoribbons and their relatively low effective mass.
Probabilistic teleportation of a quantum dot spin qubit Peer-reviewed

Y. Kojima, T. Nakajima, A. Noiri, J. Yoneda, T. Otsuka, K. Takeda, S. Li, S. D. Bartlett, A. Ludwig, A. D. Wieck, S. Tarucha

npj Quantum Information　7　(1)　2021/05

DOI： 10.1038/s41534-021-00403-4 　

eISSN： 2056-6387
Gate voltage dependence of noise distribution in radio-frequency reflectometry in gallium arsenide quantum dots Peer-reviewed

Motoya Shinozaki, Yui Muto, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Takumi Ito, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Tomohiro Otsuka

Applied Physics Express　14　(3)　2021/02

DOI： 10.35848/1882-0786/abe41f 　

ISSN： 1882-0778

eISSN： 1882-0786
Formation of quantum dots in GaN/AlGaN FETs Peer-reviewed

Tomohiro Otsuka, Takaya Abe, Takahito Kitada, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara

Scientific Reports　10　(1)　2020/09

DOI： 10.1038/s41598-020-72269-z 　

eISSN： 2045-2322
Coherence of a Driven Electron Spin Qubit Actively Decoupled from Quasistatic Noise Peer-reviewed

Takashi Nakajima, Akito Noiri, Kento Kawasaki, Jun Yoneda, Peter Stano, Shinichi Amaha, Tomohiro Otsuka, Kenta Takeda, Matthieu R. Delbecq, Giles Allison, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

Physical Review X　10　(1)　2020/03

DOI： 10.1103/PhysRevX.10.011060 　

eISSN： 2160-3308
量子デバイスの高周波測定技術―半導体量子ドット系における高周波反射測定― Peer-reviewed

Tomohiro Otsuka

固体物理　55　69-77　2020/02
Density matrix simulation of quantum error correction codes for near-term quantum devices Peer-reviewed

Chungheon Baek, Tomohiro Ostuka, Seigo Tarucha, Byung Soo Choi

Quantum Science and Technology　5　(1)　2020

DOI： 10.1088/2058-9565/ab5887 　

eISSN： 2058-9565
Quantum non-demolition measurement of an electron spin qubit Peer-reviewed

Takashi Nakajima, Akito Noiri, Jun Yoneda, Matthieu R. Delbecq, Peter Stano, Tomohiro Otsuka, Kenta Takeda, Shinichi Amaha, Giles Allison, Kento Kawasaki, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

Nature Nanotechnology　14　(6)　555-560　2019/06

DOI： 10.1038/s41565-019-0426-x 　

ISSN： 1748-3387

eISSN： 1748-3395
Spin-orbit assisted spin funnels in DC transport through a physically defined pMOS double quantum dot Peer-reviewed

Marian Marx, Jun Yoneda, Tomohiro Otsuka, Kenta Takeda, Yu Yamaoka, Takashi Nakajima, Sen Li, Akito Noiri, Tetsuo Kodera, Seigo Tarucha

Japanese Journal of Applied Physics　58　(SB)　SBBI07-1--5　2019/04
Publisher: IOP Publishing
DOI： 10.7567/1347-4065/ab01d6 　

ISSN： 0021-4922

eISSN： 1347-4065
Difference in charge and spin dynamics in a quantum dot-lead coupled system Peer-reviewed

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

Physical Review B　99　(8)　085402-1--5　2019/02
Publisher: American Physical Society (APS)
DOI： 10.1103/PhysRevB.99.085402 　

ISSN： 2469-9950

eISSN： 2469-9969
第34回半導体物理学国際会議(ICPS2018)報告

Tomohiro Otsuka

固体物理　54　55-60　2019/01
Coherent transfer of electron spin correlations assisted by dephasing noise Peer-reviewed

Takashi Nakajima, Matthieu R. Delbecq, Tomohiro Otsuka, Shinichi Amaha, Jun Yoneda, Akito Noiri, Kenta Takeda, Giles Allison, Arne Ludwig, Andreas D. Wieck, Xuedong Hu, Franco Nori, Seigo Tarucha

Nature Communications　9　(1)　2133-1--8　2018/12/01
Publisher: Nature Publishing Group
DOI： 10.1038/s41467-018-04544-7 　

ISSN： 2041-1723

eISSN： 2041-1723
A fast quantum interface between different spin qubit encodings Peer-reviewed

A. Noiri, T. Nakajima, J. Yoneda, M. R. Delbecq, P. Stano, T. Otsuka, K. Takeda, S. Amaha, G. Allison, K. Kawasaki, Y. Kojima, A. Ludwig, A. D. Wieck, D. Loss, S. Tarucha

Nature Communications　9　(1)　5066-1--7　2018/11

DOI： 10.1038/s41467-018-07522-1 　

eISSN： 2041-1723
Optimized electrical control of a Si/SiGe spin qubit in the presence of an induced frequency shift Peer-reviewed

Kenta Takeda, Jun Yoneda, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Giles Allison, Yusuke Hoshi, Noritaka Usami, Kohei M. Itoh, Shunri Oda, Tetsuo Kodera, Seigo Tarucha

npj Quantum Information　4　54-1--6　2018/10
Four single-spin Rabi oscillations in a quadruple quantum dot Peer-reviewed

Takumi Ito, Takumi Ito, Tomohiro Otsuka, Tomohiro Otsuka, Tomohiro Otsuka, Tomohiro Otsuka, Takashi Nakajima, Takashi Nakajima, Matthieu R. Delbecq, Matthieu R. Delbecq, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Jun Yoneda, Kenta Takeda, Kenta Takeda, Akito Noiri, Akito Noiri, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Seigo Tarucha, Seigo Tarucha, Seigo Tarucha

Applied Physics Letters　113　(9)　093102-1--5　2018/08

DOI： 10.1063/1.5040280 　

ISSN： 0003-6951

eISSN： 1077-3118
A quantum-dot spin qubit with coherence limited by charge noise and fidelity higher than 99.9% Peer-reviewed

Jun Yoneda, Kenta Takeda, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Giles Allison, Takumu Honda, Tetsuo Kodera, Shunri Oda, Yusuke Hoshi, Noritaka Usami, Kohei M. Itoh, Seigo Tarucha

Nature Nanotechnology　13　(2)　102-106　2018/02
Publisher: Springer Science and Business Media LLC
DOI： 10.1038/s41565-017-0014-x 　

ISSN： 1748-3387

eISSN： 1748-3395
Cotunneling spin blockade observed in a three-terminal triple quantum dot Peer-reviewed

A. Noiri, T. Takakura, T. Obata, T. Otsuka, T. Nakajima, J. Yoneda, S. Tarucha

PHYSICAL REVIEW B　96　(15)　155414-1--7　2017/10

DOI： 10.1103/PhysRevB.96.155414 　

ISSN： 2469-9950

eISSN： 2469-9969
Higher-order spin and charge dynamics in a quantum dot-lead hybrid system Peer-reviewed

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Peter Stano, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

SCIENTIFIC REPORTS　7　12201-1--7　2017/09

DOI： 10.1038/s41598-017-12217-6 　

ISSN： 2045-2322
A triangular triple quantum dot with tunable tunnel couplings Peer-reviewed

A. Noiri, K. Kawasaki, T. Otsuka, T. Nakajima, J. Yoneda, S. Amaha, M. R. Delbecq, K. Takeda, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

SEMICONDUCTOR SCIENCE AND TECHNOLOGY　32　(8)　084004-1--5　2017/08

DOI： 10.1088/1361-6641/aa7596 　

ISSN： 0268-1242

eISSN： 1361-6641
Robust Single-Shot Spin Measurement with 99.5% Fidelity in a Quantum Dot Array Peer-reviewed

Takashi Nakajima, Matthieu R. Delbecq, Tomohiro Otsuka, Peter Stano, Shinichi Amaha, Jun Yoneda, Akito Noiri, Kento Kawasaki, Kenta Takeda, Giles Allison, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

PHYSICAL REVIEW LETTERS　119　(1)　017701-1--6　2017/07

DOI： 10.1103/PhysRevLett.119.017701 　

ISSN： 0031-9007

eISSN： 1079-7114
Detection and control of charge states in a quintuple quantum dot Peer-reviewed

Takumi Ito, Tomohiro Otsuka, Shinichi Amaha, Matthieu R. Delbecq, Takashi Nakajima, Jun Yoneda, Kenta Takeda, Giles Allison, Akito Noiri, Kento Kawasaki, Seigo Tarucha

SCIENTIFIC REPORTS　6　39113-1--7　2016/12

DOI： 10.1038/srep39113 　

ISSN： 2045-2322
A fault-tolerant addressable spin qubit in a natural silicon quantum dot Peer-reviewed

Kenta Takeda, Jun Kamioka, Tomohiro Otsuka, Jun Yoneda, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Giles Allison, Tetsuo Kodera, Shunri Oda, Seigo Tarucha

SCIENCE ADVANCES　2　(8)　e1600694-1--6　2016/08

DOI： 10.1126/sciadv.1600694 　

ISSN： 2375-2548
Single-electron Spin Resonance in a Quadruple Quantum Dot Peer-reviewed

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Takumi Ito, Retsu Sugawara, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

SCIENTIFIC REPORTS　6　31820-1--6　2016/08

DOI： 10.1038/srep31820 　

ISSN： 2045-2322
Coherent electron-spin-resonance manipulation of three individual spins in a triple quantum dot Peer-reviewed

A. Noiri, J. Yoneda, T. Nakajima, T. Otsuka, M. R. Delbecq, K. Takeda, S. Amaha, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

APPLIED PHYSICS LETTERS　108　(15)　153101　2016/04

DOI： 10.1063/1.4945592 　

ISSN： 0003-6951

eISSN： 1077-3118
19pAG-14 Measurement of spin relaxation in quantum dots coupled to electric leads

Otsuka T., Nakajima T., Delbecq Matthieu, Amaha S., Yoneda J., Takeda K., Allison Giles, Noiri A., Ito T., Ludwig Arne, Wieck Andreas, Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　(1)　1319-1319　2016
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.71.1.0_1319 　

ISSN： 2189-079X
19pAG-12 Transfer of spin states to meta-stable charge configuration in a triple quantum dot

Nakajima T., Delbecq Matthieu R., Otsuka T., Amaha S., Yoneda J., Noiri A., Takeda K., Allison Giles, Ludwig Arne, Wieck Andreas, Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　1317-1317　2016
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.71.1.0_1317 　

ISSN： 2189-079X
19pAG-13 Competition between the Inhomogeneous Magnetic Field and the Exchange Interaction in the Electron Spin Resonance in a Triple Quantum Dot

Yoneda J., Noiri A., Nakajima T., Otsuka T., Delbecq Matthieu, Amaha S., Ludwig Arne, Wieck Andreas, Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　(1)　1318-1318　2016
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.71.1.0_1318 　

ISSN： 2189-079X
Single-shot readout of spin states in a triple quantum dot using a metastable charge state

Nakajima T., Delbecq M. R., Otsuka T., Yoneda J., Noiri A., Kawasaki K., Amaha S., Takeda K., Allison G., Ludwig A., Wieck A. D., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　(2)　1158-1158　2016
Publisher: The Physical Society of Japan
DOI： 10.11316/jpsgaiyo.71.2.0_1158 　

ISSN： 2189-079X
AC Stark effect of a driven spin qubit in a magnetic field gradient

Takeda K., Kamioka J., Yoneda J., Otsuka T., Delbecq M. R., Allison G., Nakajima T., Kodera T., Oda S., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　(2)　1161-1161　2016
Publisher: The Physical Society of Japan
DOI： 10.11316/jpsgaiyo.71.2.0_1161 　

ISSN： 2189-079X
The property of Rabi oscillations for a single electron spin in a quantum dot

Noiri A., Yoneda J., Nakajima T., Otsuka T., Delbecq M. R., Takeda K., Amaha S., Allison G., Ludwig A., Wieck A. D., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　71　(2)　1162-1162　2016
Publisher: The Physical Society of Japan
DOI： 10.11316/jpsgaiyo.71.2.0_1162 　

ISSN： 2189-079X
Quantum Dephasing in a Gated GaAs Triple Quantum Dot due to Nonergodic Noise Peer-reviewed

M. R. Delbecq, T. Nakajima, P. Stano, T. Otsuka, S. Amaha, J. Yoneda, K. Takeda, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

PHYSICAL REVIEW LETTERS　116　(4)　046802　2016/01

DOI： 10.1103/PhysRevLett.116.046802 　

ISSN： 0031-9007

eISSN： 1079-7114
Fast probe of local electronic states in nanostructures utilizing a single-lead quantum dot Peer-reviewed

Tomohiro Otsuka, Shinichi Amaha, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Retsu Sugawara, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

SCIENTIFIC REPORTS　5　14616　2015/09

DOI： 10.1038/srep14616 　

ISSN： 2045-2322
Robust micromagnet design for fast electrical manipulations of single spins in quantum dots Peer-reviewed

Jun Yoneda, Tomohiro Otsuka, Tatsuki Takakura, Michel Pioro-LadriSre, Roland Brunner, Hong Lu, Takashi Nakajima, Toshiaki Obata, Akito Noiri, Christopher J. Palmstrom, Arthur C. Gossard, Seigo Tarucha

APPLIED PHYSICS EXPRESS　8　(8)　084401　2015/08

DOI： 10.7567/APEX.8.084401 　

ISSN： 1882-0778

eISSN： 1882-0786
17aAG-12 Charge transport properties of a triangular triple quantum dot

Kawasaki K., Noiri A., Amaha S., Otsuka T., Nakajima T., Yoneda J., Delbecq M., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(2)　1054-1054　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.2.0_1054 　

ISSN： 2189-079X
16aAE-5 Fast and addressable single-spin operation in a Si double quantum dot

Takeda K., Kamioka J., Obata T., Otsuka T., Nakajima T., M. R. Delbecq, Amaha S., Yoneda J., G. Alison, Noiri A., Sugawara R., Kodera T., Oda S., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(2)　1006-1006　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.2.0_1006 　

ISSN： 2189-079X
16aAE-6 Coherent oscillation of entangled spin states in next-nearest neighbor quantum dots

Nakajima T., Delbecq M. R., Otsuka T., Amaha S., Yoneda J., Noiri A., Takeda K., Ludwig A., Wieck A. D., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(2)　1007-1007　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.2.0_1007 　

ISSN： 2189-079X
16aAE-2 Measurement of charge state in multiple quantum dots by multiplexed fast charge sensors

Ito T., Otsuka T., Amaha S., Nakajima T., Delbecq M., Yoneda J., Takeda K., Allison G., Noiri A., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(2)　1003-1003　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.2.0_1003 　

ISSN： 2189-079X
16aAE-1 Single-electron spin resonance in a quadruple quantum dot

Otsuka T., Nakajima T., Delbecq M., Amaha S., Yoneda J., Takeda K., Noiri A., Sugawara R., Allison G., Ludwig A., Wieck A., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(2)　1002-1002　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.2.0_1002 　

ISSN： 2189-079X
23pBK-2 Realization of a fast single-lead quantum dot probe and evaluation of the properties by probing quantum dot states

Otsuka T., Amaha S., Nakajima T., Delbecq M., Yoneda J., Takeda K., Sugawara R., Ludwig Arne, Wieck Andreas, Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(1)　1369-1369　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1369 　

ISSN： 2189-079X
23pBK-7 Improvement of slanting field ESR method by Alumina insulator layer

Ito T., Noiri A., Yoneda J., Nakajima T., Otsuka T., Amaha S., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(1)　1374-1374　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1374 　

ISSN： 2189-079X
23pBK-11 Measurement of spin-valley states in a Si double quantum dot using electron spin resonance

Takeda K., Kamioka J., Obata T., Otsuka T., Nakajima T., Delbecq M. R., Amaha S., Yoneda J., Noiri A., Sugawara R., Kodera T., Oda S., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(1)　1378-1378　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1378 　

ISSN： 2189-079X
23pBK-8 The property of resonance frequencies and Rabi frequencies of 3 spin qubits in a triple quantum dot

Noiri A., Yoneda J., Nakajima T., Otsuka T., Delbecq Matthieu, Amaha S., Ludwig Arne, Wieck Andreas D., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(1)　1375-1375　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1375 　

ISSN： 2189-079X
23pBK-10 Exploring multiple quantum dots circuits charge stability diagrams

Delbecq Matthieu, Nakajima Takashi, Otsuka Tomohiro, Amaha Shinichi, Yoneda Jun, Watson John, Manfra Michael, Tarucha Seigo

Meeting Abstracts of the Physical Society of Japan　70　1377-1377　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1377 　

ISSN： 2189-079X
23pBK-9 Fidelity improvement in spin qubits based on triple quantum dots

Nakajima T., Delbecq M. R., Otsuka T., Amaha S., Yoneda J., Noiri A., Takeda K., Ludwig Arne, Wieck Andreas D., Tarucha S.

Meeting Abstracts of the Physical Society of Japan　70　(1)　1376-1376　2015
Publisher: The Physical Society of Japan (JPS)
DOI： 10.11316/jpsgaiyo.70.1.0_1376 　

ISSN： 2189-079X
Fast Electrical Control of Single Electron Spins in Quantum Dots with Vanishing Influence from Nuclear Spins Peer-reviewed

J. Yoneda, T. Otsuka, T. Nakajima, T. Takakura, T. Obata, M. Pioro-Ladriere, H. Lu, C. J. Palmstrom, A. C. Gossard, S. Tarucha

PHYSICAL REVIEW LETTERS　113　(26)　267601　2014/12

DOI： 10.1103/PhysRevLett.113.267601 　

ISSN： 0031-9007

eISSN： 1079-7114
Single-spin manipulation in a double quantum dot in the field of a micromagnet Peer-reviewed

Stefano Chesi, Ying-Dan Wang, Jun Yoneda, Tomohiro Otsuka, Seigo Tarucha, Daniel Loss

PHYSICAL REVIEW B　90　(23)　235311　2014/12

DOI： 10.1103/PhysRevB.90.235311 　

ISSN： 1098-0121

eISSN： 1550-235X
Full control of quadruple quantum dot circuit charge states in the single electron regime Peer-reviewed

M. R. Delbecq, T. Nakajima, T. Otsuka, S. Amaha, J. D. Watson, M. J. Manfra, S. Tarucha

APPLIED PHYSICS LETTERS　104　(18)　183111　2014/05

DOI： 10.1063/1.4875909 　

ISSN： 0003-6951

eISSN： 1077-3118
Single to quadruple quantum dots with tunable tunnel couplings Peer-reviewed

T. Takakura, A. Noiri, T. Obata, T. Otsuka, J. Yoneda, K. Yoshida, S. Tarucha

APPLIED PHYSICS LETTERS　104　(11)　113109　2014/03

DOI： 10.1063/1.4869108 　

ISSN： 0003-6951

eISSN： 1077-3118
Measurement of Energy Relaxation in Quantum Hall Edge States Utilizing Quantum Point Contacts Peer-reviewed

Tomohiro Otsuka, Yuuki Sugihara, Jun Yoneda, Takashi Nakajima, Seigo Tarucha

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN　83　(1)　014710　2014/01

DOI： 10.7566/JPSJ.83.014710 　

ISSN： 0031-9015
Detection of spin polarization utilizing singlet and triplet states in a single-lead quantum dot Peer-reviewed

Otsuka, Tomohiro, Sugihara, Yuuki, Yoneda, Jun, Katsumoto, Shingo, Tarucha, Seigo

Physical Review B　86　(8)　081308(R)　2012

DOI： 10.1103/PhysRevB.86.081308 　
Aluminum oxide for an effective gate in Si/SiGe two-dimensional electron gas systems Peer-reviewed

Yun-Sok Shin, Roland Brunner, Akihiro Shibatomi, Toshiaki Obata, Tomohiro Otsuka, Jun Yoneda, Yasuhiro Shiraki, Kentarou Sawano, Yasuhiro Tokura, Yuichi Harada, Koji Ishibashi, Seigo Tarucha

SEMICONDUCTOR SCIENCE AND TECHNOLOGY　26　(5)　055004　2011/05

DOI： 10.1088/0268-1242/26/5/055004 　

ISSN： 0268-1242

eISSN： 1361-6641
Energy level spectroscopy of a quantum dot with a side-coupled satellite dot Peer-reviewed

S. W. Kim, Y. Kuwabara, T. Otsuka, Y. Iye, S. Katsumoto

PHYSICS OF SEMICONDUCTORS: 30TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF SEMICONDUCTORS　1399　393-394　2011

DOI： 10.1063/1.3666419 　

ISSN： 0094-243X
Detection of spin polarization in a quantum wire Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Iye, Yasuhiro, Katsumoto, Shingo

Physica E-Low-Dimensional Systems & Nanostructures　42　(4)　809-812　2010

DOI： 10.1016/j.physe.2009.10.034 　

ISSN： 1386-9477
Probing local electronic states in the quantum Hall regime with a side-coupled quantum dot Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Iye, Yasuhiro, Katsumoto, Shingo

Physical Review B　81　(24)　245302　2010

DOI： 10.1103/PhysRevB.81.245302 　
Detection of spin polarization with a side-coupled quantum dot Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Iye, Yasuhiro, Katsumoto, Shingo

Physical Review B　79　(19)　195313　2009

DOI： 10.1103/PhysRevB.79.195313 　
Control of shell filling with Coulomb interaction in quantum dots side-coupled to quantum wires Peer-reviewed

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 9　5　(9)　2873-2875　2008

ISSN： 1610-1634
Potential dependent intra-dot Coulomb interaction in quantum dots side-coupled to quantum wires Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Iye, Yasuhiro, Katsumoto, Shingo

Physica E-Low-Dimensional Systems & Nanostructures　40　(5)　1270-1272　2008

DOI： 10.1016/j.physe.2007.08.048 　

ISSN： 1386-9477
Control of shell filling with Coulomb interaction in quantum dots side-coupled to quantum wires Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Iye, Yasuhiro, Katsumoto, Shingo

Physica Status Solidi C - Current Topics in Solid State Physics, Vol 5, No 9　5　2873-2875　2008

DOI： 10.1002/pssc.200779183 　

ISSN： 1862-6351
Excited-state spectroscopy on a quantum dot side coupled to a quantum wire Peer-reviewed

Otsuka, T., Abe, E., Iye, Y., Katsumoto, S.

Applied Physics Letters　93　(11)　112111　2008

DOI： 10.1063/1.2987424 　
Phase information from two-terminal conductance of quantum dot systems Peer-reviewed

Otsuka, Tomohiro, Aikawa, Hisashi, Eto, Mikio, Khym, Gyong L., Kang, Kicheon, Iye, Yasuhiro, Katsumoto, Shingo

Physics of Semiconductors, Pts a and B　893　855-856　2007

DOI： 10.1063/1.2730160 　

ISSN： 0094-243X
Fano effect in a few-electron quantum dot Peer-reviewed

Otsuka, Tomohiro, Abe, Eisuke, Katsumoto, Shingo, Iye, Yasuhiro, Khym, Gyong L., Kang, Kicheon

Journal of the Physical Society of Japan　76　(8)　084706　2007

DOI： 10.1143/JPSJ.76.084706 　
Breakdown of phase rigidity and variations of the Fano effect in closed Aharonov-Bohm interferometers Peer-reviewed

Aharony, A, Entin-Wohlman, O, Otsuka, T, Katsumoto, S, Aikawa, H, Kobayashi, K

Physical Review B　73　(19)　195329　2006

DOI： 10.1103/PhysRevB.73.195329

Show all ︎Show first 5

Misc. 142

Automated Spin Readout Signal Analysis Using U-Net with Variable-Length Traces and Experimental Noise

Yui Muto, Motoya Shinozaki, Hideaki Yuta, Tatsuo Tsuzuki, Kotaro Taga, Akira Oiwa, Takafumi Fujita, Tomohiro Otsuka

2026/02/02

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Single-shot spin-state discrimination is essential for semiconductor spin qubits, but conventional threshold-based analysis of spin readout traces becomes unreliable under noisy conditions. Although recent neural-network-based methods improve robustness against experimental noise, they are sensitive to training conditions, restricted to fixed-length inputs, and limited to trace-level outputs without explicit temporal localization of transition events. In this work, we apply a U-Net architecture to spin readout signal analysis by formulating transition-event detection as a point-wise segmentation task in one-dimensional time-series data. The fully convolutional structure enables direct processing of variable-length traces. Point-wise and sample-wise evaluations demonstrate low readout error rates and high classification accuracy without retraining. The proposed method generalizes well to previously-unseen trace lengths and experimental non-Gaussian noise, outperforming a conventional threshold-based approach and providing a robust and practical solution for automated spin readout signal analysis.
Perfect impedance matching unlocks sensitive radio-frequency reflectometry in 2D material quantum dots

Motoya Shinozaki, Akitomi Shirachi, Yuta Kera, Tomoya Johmen, Shunsuke Yashima, Aruto Hosaka, Tsuyoshi Yoshida, Takeshi Kumasaka, Yusuke Kozuka, Tomohiro Otsuka

2025/12/01

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Two-dimensional (2D) materials are attractive platforms for realizing high-performance quantum bits (qubits). However, radio-frequency (RF) charge detection, which is a key technique for qubits readout, remains challenging in such systems. We demonstrate RF reflectometry with impedance matching for high-resistance quantum dot devices based on bilayer graphene and molybdenum disulfide. By integrating a tunable strontium titanate (SrTiO3) varactor into a resonant circuit, we achieve nearly perfect impedance matching, enabling sensitive charge detection. The demodulated RF signal clearly shows Coulomb oscillations, and the SrTiO3 varactor exhibits robustness against both magnetic fields and voltage noise on the varactor. Our results establish SrTiO3 varactors as effective tunable matching components for RF reflectometry in high-resistance 2D material quantum devices, providing a foundation for high-speed qubits readout.
Magnetotransport and Coulomb Blockade in Single InAs Colloidal Quantum Dot Transistors

Kenji Shibata, Tomoki Takiguchi, Akira Sato, Yuto Sasaki, Tomohiro Otsuka

2025/08/25
Publisher: American Chemical Society (ACS)
DOI： 10.26434/chemrxiv-2025-t4cdv 　
Quantum dot transistors based on CVD-grown graphene nano islands

Takumi Seo, Motoya Shinozaki, Akiko Tada, Yuta Kera, Shunsuke Yashima, Kosuke Noro, Takeshi Kumasaka, Azusa Utsumi, Takashi Matsumoto, Yoshiyuki Kobayashi, Tomohiro Otsuka

2025/06/09

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Graphene nanoislands (GNIs) are one of the promising building blocks for quantum devices owing to their unique potential. However, direct electrical measurements of GNIs have been challenging due to the requirement of metal catalysts in typical synthesis methods. In this study, we demonstrate electrical transport measurements of GNIs by using microwave plasma chemical vapor deposition, which is a catalyst-free method to deposit graphene directly on SiO$_2$ substrates. This approach enables the fabrication of metal electrodes on GNIs, allowing us to measure their quantum transport properties. At low temperatures, one of our devices shows clear Coulomb diamonds with twofold degeneracy, indicating the formation of quantum dots and the vanishing of valley degeneracy. The charge state of the GNI is also modulated by a local side gate, and the tunneling coupling between leads and quantum dots is modulated by changing contact area and metal materials. These results provide device design guidelines toward GNI-based quantum devices for next-generation computing.
On-chip calibrated radio-frequency measurement at cryogenic temperatures for determination of SrTiO3-based capacitor properties

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Hisashi Inoue, Kenta Itoh, Yusuke Kozuka, Takanobu Watanabe, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

2025/04/28

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Quantum computing has emerged as a promising technology for next-generation information processing, utilizing semiconductor quantum dots as one of the candidates for quantum bits. Radio-frequency (rf) reflectometry plays an important role in the readout of quantum dots but requires a precise rf measurement technique at cryogenic temperatures. While cryogenic calibration techniques, essential for rf reflectometry, have been developed, on-chip calibration near the device remains an important challenge. In this study, we develop an on-chip calibrated rf measurement system operating at 4K for characterizing SrTiO3-based varactors, which are promising components for tunable impedance matching circuits. Our system enables accurate measurements by eliminating errors associated with long rf circuit lines. We investigate the effects of annealing conditions, crystal orientation, and Ca doping of SrTiO3 crystals on the varactor properties in the frequency range for rf reflectometry. Our results provide insights for optimizing these components for cryogenic rf applications in quantum information processing systems.
Formation of multiple quantum dots in ZnO heterostructures

Koichi Baba, Kosuke Noro, Yusuke Kozuka, Takeshi Kumasaka, Motoya Shinozaki, Masashi Kawasaki, Tomohiro Otsuka

2025/04/03

DOI： 10.1038/s41598-025-20567-9 　

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In recent years, advancements in semiconductor manufacturing technology have enabled the formation of high-quality, high-mobility two-dimensional electron gases in zinc oxide (ZnO) heterostructures, making the electrostatic formation of quantum dots possible. ZnO, with its low natural abundance of isotopes possessing nuclear spin and its direct bandgap, is considered a potentially suitable material for quantum bit applications. In this study, we achieve the formation of triple quantum dots and the realization of a few-electron state in ZnO heterostructure devices. We also confirm that by varying the gate voltage between the quantum dots, it is possible to control the interdot spacing. Additionally, we observe a tunneling phenomenon called a quantum cellular automata effect, where multiple electrons move simultaneously, which is not seen in single or double quantum dots, due to Coulomb interactions. Our results demonstrate that ZnO nanostructures have reached a level where they can function as controllable multiple quantum dot systems.
RFSoC-based radio-frequency reflectometry in gate-defined bilayer graphene quantum devices

Motoya Shinozaki, Tomoya Johmen, Aruto Hosaka, Takumi Seo, Shunsuke Yashima, Akitomi Shirachi, Kosuke Noro, Shoichi Sato, Takashi Kumasaka, Tsuyoshi Yoshida, Tomohiro Otsuka

2025/02/21

DOI： 10.35848/1882-0786/ade6c2 　

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Quantum computers require both scalability and high performance for practical applications. While semiconductor quantum dots are promising candidates for quantum bits, the complexity of measurement setups poses an important challenge for scaling up these devices. Here, radio-frequency system-on-chip (RFSoC) technology is exepcted for a promising approach that combines scalability with flexibility. In this paper, we demonstrate RF reflectometry in gate-defined bilayer graphene quantum devices using RFSoC-based measurement architecture. By controlling the confinement strength through gate voltages, we achieve both Fabry-Pérot interferometer and quantum dot operations in a single device. Although impedance matching conditions currently limit the measurement sensitivity, we identify pathways for optimization through tunnel barrier engineering and resonator design. These results represent a step toward integrating high-bandwidth measurements with scalable quantum devices.
Automatic detection of single-electron regime of quantum dots and definition of virtual gates using U-Net and clustering

Yui Muto, Michael R. Zielewski, Motoya Shinozaki, Kosuke Noro, Tomohiro Otsuka

2025/01/10

DOI： 10.1038/s41598-026-38889-7 　

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To realize practical quantum computers, a large number of quantum bits (qubits) will be required. Semiconductor spin qubits offer advantages such as high scalability and compatibility with existing semiconductor technologies. However, as the number of qubits increases, manual qubit tuning becomes infeasible, motivating automated tuning approaches. In this study, we use U-Net, a neural network method for object detection, to identify charge transition lines in experimental charge stability diagrams. The extracted charge transition lines are analyzed using the Hough transform to determine their positions and angles. Based on this analysis, we obtain the transformation matrix to virtual gates. Furthermore, we identify the single-electron regime by clustering the Hough transform outputs. We also show the single-electron regime within the virtual gate space. These sequential processes are performed automatically. This approach will advance automated control technologies for large-scale quantum devices.
Charge sensing of few-electron ZnO double quantum dots probed by radio-frequency reflectometry

Kosuke Noro, Motoya Shinozaki, Yusuke Kozuka, Kazuma Matsumura, Yoshihiro Fujiwara, Takeshi Kumasaka, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

2025/01/09

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Zinc oxide (ZnO) has garnered much attention as a promising material for quantum devices due to its unique characteristics. To utilize the potential of ZnO for quantum devices, the development of fundamental technological elements such as high-speed readout and charge sensing capabilities has become essential. In this study, we address these challenges by demonstrating radio-frequency (rf) reflectometry and charge sensing in ZnO quantum dots, thus advancing the potential for qubit applications. A device is fabricated on a high-quality ZnO heterostructure, featuring gate-defined target and sensor quantum dots. The sensor dot, integrated into an rf resonator circuit, enables the detection of single-electron charges in the target dots. Using this setup, the formation of few-electron double quantum dots is observed by obtaining their charge stability diagram. Also, a charge stability diagram with a gate pulse sequence is measured. We discuss the strong electron correlation in ZnO, which leads to nearly degenerate spin-singlet and -triplet two-electron states in the (0, 2) charge state, and the perspectives on spin-state readout.
Automation of Single-Electron Regime Detection and Virtual Gate Definition in Quantum Dots Using Machine Learning

武藤由依, ZIELEWSKI Michael R., 篠崎基矢, 野呂康介, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　80　(1)　2025

ISSN： 2189-079X
Formation of Few-Electron ZnO Double Quantum Dots

野呂康介, 野呂康介, 篠崎基矢, 小塚裕介, 松村和真, 松村和真, 藤原義弘, 藤原義弘, 熊坂武志, 塚崎敦, 川崎雅司, 川崎雅司, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　80　(1)　2025

ISSN： 2189-079X
Electron transport through single InAs colloidal quantum dots

柴田憲治, 滝口智稀, 佐藤明, 佐々木悠人, 大塚朋廣

応用物理学会学術講演会講演予稿集(CD-ROM)　86th　2025

ISSN： 2436-7613
Process Optimization of Control of Contact Interface for Integrated Graphene Josephson Junctions

小倉宏斗, 小倉宏斗, LI Zhuoqun, LI Zhuoqun, 内海あずさ, 大塚朋廣, 大塚朋廣, 大塚朋廣, 加藤俊顕, 加藤俊顕

応用物理学会学術講演会講演予稿集(CD-ROM)　86th　2025

ISSN： 2436-7613
Probing electron trapping by current collapse in GaN/AlGaN FETs utilizing quantum transport characteristics

Takaya Abe, Motoya Shinozaki, Kazuma Matsumura, Takumi Aizawa, Takeshi Kumasaka, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

2024/08/07

DOI： 10.1063/5.0232463 　

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GaN is expected to be a key material for next-generation electronics due to its interesting properties. However, the current collapse poses a challenge to the application of GaN FETs to electronic devices. In this study, we investigate the formation of quantum dots in GaN FETs under the current collapse. By comparing the Coulomb diamond between standard measurements and those under current collapse, we find that the gate capacitance is significantly decreased by the current collapse. This suggests that the current collapse changes the distribution of trapped electrons at the device surface, which is reported in the previous study by operando X-ray spectroscopy. Also, we show external control of quantum dot formation, previously challenging in an FET structure, by using current collapse.
Charge state estimation in quantum dots using a Bayesian approach

Motoya Shinozaki, Yui Muto, Takahito Kitada, Tomohiro Otsuka

2024/08/06

DOI： 10.1103/PhysRevApplied.23.034078 　

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Detection of single-electron charges in solid-state nanodevices is a key technique in semiconductor quantum bit readout for quantum information processing and probing electronic properties of nanostructures. This detection is achieved using quantum dot charge sensors, with its speed enhanced by high-speed RF reflectometry. Recently, real-time processing of data from RF reflectometry has attracted much attention to quantum information processing. In this paper, we propose a sequential method based on Bayes' theorem for estimating the charge state and compare its performance with the averaging approach and threshold judgment. When the noise variance differs between the empty and occupied states, the Bayesian approach demonstrates a lower error score, facilitating the extraction of more data points in real-time charge state estimation. Additionally, the Bayesian approach outperforms the averaging method and threshold judgment in terms of error rates for charge state estimation, even during charge transitions. This technique is broadly applicable to single-electron detection and holds substantial utility for quantum bit readout and the operation of nanoprobes that utilize single-electron detection.
Lattice-guided growth of dense arrays of aligned transition metal dichalcogenide nanoribbons with high catalytic reactivity

Zongpeng Ma, Pablo Solís-Fernández, Kaito Hirata, Yung-Chang Lin, Keisuke Shinokita, Mina Maruyama, Kota Honda, Tatsuki Kato, Aika Uchida, Hiroto Ogura, Tomohiro Otsuka, Masahiro Hara, Kazunari Matsuda, Kazu Suenaga, Susumu Okada, Toshiaki Kato, Yasufumi Takahashi, Hiroki Ago

2024/07/13

DOI： 10.1126/sciadv.adr8046 　

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Transition metal dichalcogenides (TMDs) exhibit unique properties and potential applications when reduced to one-dimensional (1D) nanoribbons (NRs), owing to quantum confinement and high edge densities. However, effective growth methods for self-aligned TMD NRs are still lacking. We demonstrate a versatile approach for lattice-guided growth of dense, aligned MoS2 NR arrays via chemical vapor deposition (CVD) on anisotropic sapphire substrates, without tailored surface steps. This method enables the synthesis of NRs with widths below 10 nm and longitudinal axis parallel to the zigzag direction, being also extensible to the growth of WS2 NRs and MoS2-WS2 hetero-nanoribbons. Growth is influenced by both substrate and CVD temperature, indicating the role of anisotropic precursor diffusion and substrate interaction. The 1D nature of the NRs was asserted by the observation of Coulomb blockade at low temperature. Pronounced catalytic activity was observed at the edges of the NRs, indicating their promise for efficient catalysis.
Microwave dependent quantum transport characteristics in GaN/AlGaN FETs

Motoya Shinozaki, Takaya Abe, Kazuma Matsumura, Takumi Aizawa, Takashi Kumasaka, Tomohiro Otsuka

2024/04/17

DOI： 10.1103/PhysRevB.110.035305 　

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Defects in semiconductors, traditionally seen as detrimental to electronic device performance, have emerged as potential assets in quantum technologies due to their unique quantum properties. This study investigates the interaction between defects and quantum electron transport in GaN/AlGaN field-effect transistors, highlighting the observation of Fano resonances at low temperatures. We observe the resonance spectra and their dependence on gate voltage and magnetic fields. To explain the observed behavior, we construct the possible scenario as a Fano interferometer with finite width. Our findings reveal the potential of semiconductor defects to contribute to the development of quantum information processing, providing their role to key components in next-generation quantum devices.
Dynamics of quantum cellular automata electron transition in triple quantum dots

Takumi Aizawa, Motoya Shinozaki, Yoshihiro Fujiwara, Takeshi Kumasaka, Wataru Izumida, Arne Ludwig, Andreas D. Wieck, Tomohiro Otsuka

2024/03/10

DOI： 10.1103/PhysRevB.110.235421 　

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The quantum cellular automata (QCA) effect is a transition in which multiple electron move coordinately by Coulomb interactions and observed in multiple quantum dots. This effect will be useful for realizing and improving quantum cellular automata and information transfer using multiple electron transfer. In this paper, we investigate the real-time dynamics of the QCA charge transitions in a triple quantum dot by using fast charge-state readout realized by rf reflectometry. We observe real-time charge transitions and analyze the tunneling rate comparing with the first-order tunneling processes. We also measure the gate voltage dependence of the QCA transition and show that it can be controlled by the voltage.
Studies for Quantum-Classic Hybrid Systems Employing Logics and Algorithms in Digital Communications

越川翔太, 保坂有杜, 西川翔太, 小西良明, 篠崎基矢, 大塚朋廣, WAIDYASOORIYA Hasitha Muthumala, 張山昌論, 吉田剛

電子情報通信学会技術研究報告(Web)　123　(329(CS2023 93-103))　2024

ISSN： 2432-6380
Analysis of RF resonance peaks in GaN FETs

松村和真, 阿部峰也, 篠崎基矢, 相澤拓海, 熊坂武志, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　79　(1)　2024

ISSN： 2189-079X
Analysis of Kondo effect in ZnO quantum dots

野呂康介, 野呂康介, 松村和真, 松村和真, 熊坂武志, 小塚裕介, 塚崎敦, 塚崎敦, 川崎雅司, 川崎雅司, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　79　(1)　2024

ISSN： 2189-079X
半導体量子デバイスの放射線に対する応答の研究

高草元, 岸本康弘, 吉田斉, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　79　(1)　2024

ISSN： 2189-079X
Development of a single shot detector of an electron wave packet using a spin qubit

JANG Yunseong, TU Han Ngoc, 藤田高史, 大塚朋廣, LUDWIG Arne, WIECK Andreas D., 山本倫久, BAEUERLE Christopher, 新見康洋, 新見康洋, 高田真太郎, 高田真太郎

日本物理学会講演概要集(CD-ROM)　79　(2)　2024

ISSN： 2189-079X
Local anodic oxidation of suspended graphene using atomic force microscope

田中奎伍, 柿添勇成, 松井朋裕, 大塚朋廣, 原正大, 原正大

日本物理学会講演概要集(CD-ROM)　79　(2)　2024

ISSN： 2189-079X
Crystal orientation and doping dependence of SrTiO₃-based capacitor for cryogenic variable microwave resonators

白地昭豊鏡, 篠崎基矢, 富岡泰秀, 小塚裕介, 佐藤彰一, 熊坂武志, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　79　(2)　2024

ISSN： 2189-079X
Radio-frequency reflectometry in semiconductor quantum devices by RFSoC

篠崎基矢, 上面友也, 上面友也, 保坂有杜, 瀬尾拓未, 瀬尾拓未, 八島俊介, 八島俊介, 白地昭豊鏡, 白地昭豊鏡, 野呂康介, 野呂康介, 佐藤彰一, 熊坂武志, 吉田剛, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　79　(2)　2024

ISSN： 2189-079X
Electron transport through single perovskite quantum dots

高橋央輔, 大塚朋廣, 大塚朋廣, 柴田憲治

応用物理学会春季学術講演会講演予稿集(CD-ROM)　71st　2024

ISSN： 2758-4704
Evaluation of microwave properties of NbN thin film on high permittivity substrate for compact superconducting Traveling-Wave Parametric Amplifier

沓間弘樹, 沓間弘樹, 森俊祐, 小塚裕介, 大塚朋廣, 松浦康平, 山下太郎

応用物理学会春季学術講演会講演予稿集(CD-ROM)　71st　2024

ISSN： 2758-4704
Electron transport through single perovskite quantum dots proved by nanogap metal leads

高橋央輔, 大塚朋廣, 大塚朋廣, 柴田憲治

応用物理学会秋季学術講演会講演予稿集(CD-ROM)　85th　2024

ISSN： 2758-4704
Electric-double-layer transistors with single colloidal PbS quantum dots

滝口智稀, 高橋央輔, 大塚朋廣, 大塚朋廣, 柴田憲治

応用物理学会秋季学術講演会講演予稿集(CD-ROM)　85th　2024

ISSN： 2758-4704
Kondo effect in electrostatically defined ZnO quantum dots

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

2023/11/21

DOI： 10.1038/s41467-024-53890-2 　

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Quantum devices such as spin qubits have been extensively investigated in electrostatically confined quantum dots using high-quality semiconductor heterostructures like GaAs and Si. Here, we present the first demonstration of electrostatically forming the quantum dots in ZnO heterostructures. Through the transport measurement, we uncover the distinctive signature of the Kondo effect independent of the even-odd electron number parity, which contrasts with the typical behavior of the Kondo effect in GaAs. By analyzing temperature and magnetic field dependences, we find that the absence of the even-odd parity in the Kondo effect is not straightforwardly interpreted by the considerations developed for conventional semiconductors. We propose that, based on the unique parameters of ZnO, electron correlation likely plays a fundamental role in this observation. Our study not only clarifies the physics of correlated electrons in the quantum dot but also holds promise for applications in quantum devices, leveraging the unique features of ZnO.
Wide dynamic range charge sensor operation by high-speed feedback control of radio-frequency reflectometry

Yoshihiro Fujiwara, Motoya Shinozaki, Kazuma Matsumura, Kosuke Noro, Riku Tataka, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

2023/07/11

DOI： 10.1063/5.0167212 　

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Semiconductor quantum dots are useful for controlling and observing quantum states and can also be used as sensors for reading out quantum bits and exploring local electronic states in nanostructures. However, challenges remain for the sensor applications, such as the trade-off between sensitivity and dynamic range and the issue of instability due to external disturbances. In this study, we demonstrate proportional-integral-differential feedback control of the radio-frequency reflectometry in GaN nanodevices using a field-programmable gate array. This technique can maintain the operating point of the charge sensor with high sensitivity. The system also realizes a wide dynamic range and high sensor sensitivity through the monitoring of the feedback signal. This method has potential applications in exploring dynamics and instability of electronic and quantum states in nanostructures.
Channel length dependence of the formation of quantum dots in GaN/AlGaN FETs

Kazuma Matsumura, Takaya Abe, Takahito Kitada, Takeshi Kumasaka, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

2023/04/13

DOI： 10.35848/1882-0786/ace415 　

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Quantum dots can be formed in simple GaN/AlGaN field-effect-transistors (FETs) by disordered potential induced by impurities and defects. Here, we investigate the channel length dependence of the formation of quantum dots. We observe decrease of the number of formed quantum dots with decrease of the FET channel length. A few quantum dots are formed in the case with the gate length of 0.05~$μ$m and we evaluate the dot parameters and the disordered potential. We also investigate the effects of a thermal cycle and illumination of light, and reveal the change of the disordered potential.
Improving the dynamic range of a charge sensor through high-speed PID control of radio-frequency reflectometry

篠崎基矢, 藤原義弘, 藤原義弘, 松村和真, 松村和真, 野呂康介, 野呂康介, 田高陸, 田高陸, 佐藤彰一, 熊坂武志, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　78　(2)　2023

ISSN： 2189-079X
Formation of a few quantum dots in short channel GaN FETs

松村和真, 阿部峰也, 北田孝仁, 熊坂武志, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　78　(2)　2023

ISSN： 2189-079X
Electron transport through single colloidal PbS quantum dots

柴田憲治, 吉田政希, 平川一彦, 大塚朋廣, BISRI Satria, BISRI Satria, 岩佐義宏, 岩佐義宏

日本物理学会講演概要集(CD-ROM)　78　(2)　2023

ISSN： 2189-079X
Electron transport through single colloidal PbS quantum dots

柴田憲治, 吉田政希, 平川一彦, 大塚朋廣, BISRI Satria, BISRI Satria, 岩佐義宏, 岩佐義宏

応用物理学会秋季学術講演会講演予稿集(CD-ROM)　84th　2023

ISSN： 2758-4704
Electron transport through single colloidal PbS quantum dots coupled to nanogap metal electrodes

吉田政希, 阿部真弓, 平川一彦, 大塚朋廣, BISRI Satria, BISRI Satria, 岩佐義宏, 岩佐義宏, 柴田憲治

応用物理学会春季学術講演会講演予稿集(CD-ROM)　70th　2023

ISSN： 2758-4704
Visual explanations of the machine learning model to recognize the charge states in quantum dots

武藤由依, 中曽拓, 相澤拓海, 篠崎基矢, 北田孝仁, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　78　(1)　2023

ISSN： 2189-079X
Improving generalization ability of automatic charge-state estimation in quantum dots by machine learning

武藤由依, 中曽拓, 相澤拓海, 篠崎基矢, 北田孝仁, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　78　(2)　2023

ISSN： 2189-079X
Radio-frequency reflectometry in bilayer graphene devices utilizing micro graphite back-gates

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Takumi Aizawa, Tomohiro Otsuka

2022/11/30

DOI： 10.1103/PhysRevApplied.20.014035 　

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Bilayer graphene is an attractive material that realizes high-quality two-dimensional electron gas with a controllable bandgap. By utilizing the bandgap, electrical gate tuning of the carrier is possible and formation of nanostructures such as quantum dots have been reported. To probe the dynamics of the electronics states and realize applications for quantum bit devices, RF-reflectometry which enables high-speed electric measurements is important. Here we demonstrate RF-reflectometry in bilayer graphene devices. We utilize a micro graphite back-gate and an undoped Si substrate to reduce the parasitic capacitance which degrades the RF-reflectometry. We measure the resonance properties of a tank circuit which contains the bilayer graphene device. We form RF-reflectmetory setup and compared the result with the DC measurement, and confirmed their consistency. We also measure Coulomb diamonds of quantum dots possibly formed by bubbles and confirm that RF-reflectometry of quantum dots can be performed. This technique enables high-speed measurements of bilayer graphene quantum dots and contributes to the research of bilayer graphene-based quantum devices by fast readout of the states.
Visual explanations of machine learning model estimating charge states in quantum dots

Yui Muto, Takumi Nakaso, Motoya Shinozaki, Takumi Aizawa, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

2022/10/26

DOI： 10.1063/5.0193621 　

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Charge state recognition in quantum dot devices is important in the preparation of quantum bits for quantum information processing. Toward auto-tuning of larger-scale quantum devices, automatic charge state recognition by machine learning has been demonstrated. For further development of this technology, an understanding of the operation of the machine learning model, which is usually a black box, will be useful. In this study, we analyze the explainability of the machine learning model estimating charge states in quantum dots by gradient-weighted class activation mapping, which identified class-discriminative regions for the predictions. The model predicts the state based on the change transition lines, indicating that human-like recognition is realized. We also demonstrate improvements of the model by utilizing feedback from the mapping results. Due to the simplicity of our simulation and pre-processing methods, our approach offers scalability without significant additional simulation costs, demonstrating its suitability for future quantum dot system expansions.
Formation of quantum dots in MoS2 with cryogenic Bi contacts and intrinsic Schottky barriers

Riku Tataka, Alka Sharma, Tomoya Johmen, Takeshi Kumasaka, Motoya Shinozaki, Yong P. Chen, Tomohiro Otsuka

2022/10/21

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The recent advancement in two-dimensional (2D) materials-based quantum confinement has provided an opportunity to investigate and manipulate electron transport for quantum applications. However, the issues of metal/semiconductor interface effects create a hurdle to realize the artificial fabrication of the quantum dot and study the quantum transport. Here, we utilize the strategy of employing the semimetal for Ohmic contacts with transition metal dichalcogenides especially, multilayer MoS2 and successfully fabricate the MoS2-Bi based FET devices. We observe the Ohmic behavior in the MoS2-Bi devices at cryogenic temperatures 4.2, 2.3 and 0.4 K. We also utilize intrinsic Schottky barriers formed at the interface between MoS2 and Au for the gate electrodes to form and control quantum dots. We observed Coulomb diamonds in MoS2 devices at cryogenic temperature. Our results of quantum transport in MoS2 could serve as a stepping stone for investigating novel quantum effects such as spin-valley coupling and the manipulation of qubit systems.
Radio-frequency reflectometry in bilayer graphene nanodevices

上面友也, 篠崎基矢, 藤原義弘, 田高陸, 熊坂武志, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(2)　2022

ISSN： 2189-079X
Radiation Response of Quantum Point Contacts

湯田秀明, 吉田斉, 大塚朋廣, 岸本康宏

日本物理学会講演概要集(CD-ROM)　77　(1)　2022

ISSN： 2189-079X
Nonlinear electron transport properties in nanoscale CoFeB/MgO magnetic tunnel junctions

篠崎基矢, 篠崎基矢, 五十嵐純太, 五十嵐純太, 岩切秀一, 北田孝仁, 北田孝仁, 早川佳祐, 早川佳祐, 陣内佛霖, 大塚朋廣, 大塚朋廣, 大塚朋廣, 大塚朋廣, 深見俊輔, 深見俊輔, 深見俊輔, 深見俊輔, 深見俊輔, 深見俊輔, 小林研介, 大野英男, 大野英男, 大野英男, 大野英男, 大野英男, 大野英男

日本物理学会講演概要集(CD-ROM)　77　(1)　2022

ISSN： 2189-079X
Formation of quantum dots in GaN FETs under the current collapse

阿部峰也, 篠崎基矢, 相澤拓海, 熊坂武志, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(1)　2022

ISSN： 2189-079X
Formation of quantum dots and Kondo effects in ZnO

野呂康介, 熊坂武志, 藤原義弘, 小塚裕介, 塚崎敦, 川崎雅司, 川崎雅司, 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(2)　2022

ISSN： 2189-079X
Ohmic contacts and gate electrodes in MoS2 and formation of quantum dots

田高陸, SHARMA Alka, 上面友也, 篠崎基矢, 熊坂武志, CHEN Yong P., CHEN Yong P., 大塚朋廣, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(2)　2022

ISSN： 2189-079X
Electron transport through colloidal PbS quantum dots coupled to nanogap metal electrodes

柴田憲治, 齋藤光貴, 大塚朋廣

応用物理学会春季学術講演会講演予稿集(CD-ROM)　69th　2022

ISSN： 2758-4704
Noise-robust charge state recognition in quantum dots using machine learning and preprocessing

武藤由依, 中曽拓, 相澤拓海, 篠崎基矢, 北田孝仁, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 兼村厚範, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(1)　2022

ISSN： 2189-079X
Real-time measurement of QCA charge state transition in quantum dots by rf-reflectometry

相澤拓海, 篠崎基矢, 藤原義弘, 熊坂武志, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　77　(1)　2022

ISSN： 2189-079X
Channel length dependence of the formation of quantum dots in GaN FETs

阿部峰也, 北田孝仁, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　76　(1)　2021

ISSN： 2189-079X
Measurement and control of electron spin states utilizing semiconductor quantum dots

大塚朋廣

日本物理学会講演概要集(CD-ROM)　76　(1)　2021

ISSN： 2189-079X
Formation of a single quantum dot in a CVD graphene nanoribbon

北田孝仁, 阿部峰也, 瀬尾瑞樹, 佐藤尚郁, 篠崎基矢, 相澤拓海, 武藤由依, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　76　(1)　2021

ISSN： 2189-079X
RF dependent electronic transport in GaN FETs

阿部峰也, 篠崎基矢, 相澤拓海, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　76　(2)　2021

ISSN： 2189-079X
Gate modulation of conductance in metal quantum point contacts

柴田憲治, 佐々木尚人, 斉藤大我, 大塚朋廣, 平川一彦

応用物理学会春季学術講演会講演予稿集(CD-ROM)　68th　2021

ISSN： 2758-4704
Gate voltage dependence of noise distribution in radio-frequency reflectometry in gallium arsenide quantum dots

Motoya Shinozaki, Yui Muto, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Takumi Ito, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Tomohiro Otsuka

2020/12/08

DOI： 10.35848/1882-0786/abe41f 　

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We investigate gate voltage dependence of electrical readout noise in high-speed rf reflectometry using gallium arsenide quantum dots. The fast Fourier transform spectrum from the real time measurement reflects build-in device noise and circuit noise including the resonator and the amplifier. We separate their noise spectral components by model analysis. Detail of gate voltage dependence of the flicker noise is investigated and compared to the charge sensor sensitivity. We point out that the dominant component of the readout noise changes by the measurement integration time.
Spin orbit field in a physically defined p type MOS silicon double quantum dot

Marian Marx, Jun Yoneda, Ángel Gutiérrez Rubio, Peter Stano, Tomohiro Otsuka, Kenta Takeda, Sen Li, Yu Yamaoka, Takashi Nakajima, Akito Noiri, Daniel Loss, Tetsuo Kodera, Seigo Tarucha

2020/03/16

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We experimentally and theoretically investigate the spin orbit (SO) field in a physically defined, p type metal oxide semiconductor double quantum dot in silicon. We measure the magnetic field dependence of the leakage current through the double dot in the Pauli spin blockade. A finite magnetic field lifts the blockade, with the lifting least effective when the external and SO fields are parallel. In this way, we find that the spin flip of a tunneling hole is due to a SO field pointing perpendicular to the double dot axis and almost fully out of the quantum well plane. We augment the measurements by a derivation of SO terms using group symmetric representations theory. It predicts that without in plane electric fields (a quantum well case), the SO field would be mostly within the plane, dominated by a sum of a Rashba and a Dresselhaus like term. We, therefore, interpret the observed SO field as originated in the electric fields with substantial in plane components.
Formation of quantum dots in GaN/AlGaN FETs

Tomohiro Otsuka, Takaya Abe, Takahito Kitada, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara

2020/02/09

DOI： 10.1038/s41598-020-72269-z 　

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GaN and the heterostructures are attractive in condensed matter science and applications for electronic devices. We measure the electron transport in GaN/AlGaN field-effect transistors (FETs) at cryogenic temperature. We observe formation of quantum dots in the conduction channel near the depletion of the 2-dimensional electron gas (2DEG). Multiple quantum dots are formed in the disordered potential induced by impurities in the FET conduction channel. We also measure the gate insulator dependence of the transport properties. These results can be utilized for the development of quantum dot devices utilizing GaN/AlGaN heterostructures and evaluation of the impurities in GaN/AlGaN FET channels.
Coherence of a driven electron spin qubit actively decoupled from quasi-static noise

Takashi Nakajima, Akito Noiri, Kento Kawasaki, Jun Yoneda, Peter Stano, Shinichi Amaha, Tomohiro Otsuka, Kenta Takeda, Matthieu R. Delbecq, Giles Allison, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

2020/01/09

DOI： 10.1103/PhysRevX.10.011060 　

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The coherence of electron spin qubits in semiconductor quantum dots suffers mostly from low-frequency noise. During the last decade, efforts have been devoted to mitigate such noise by material engineering, leading to substantial enhancement of the spin dephasing time for an idling qubit. However, the role of the environmental noise during spin manipulation, which determines the control fidelity, is less understood. We demonstrate an electron spin qubit whose coherence in the driven evolution is limited by high-frequency charge noise rather than the quasi-static noise inherent to any semiconductor device. We employed a feedback control technique to actively suppress the latter, demonstrating a $π$-flip gate fidelity as high as $99.04\pm 0.23\,\%$ in a gallium arsenide quantum dot. We show that the driven-evolution coherence is limited by the longitudinal noise at the Rabi frequency, whose spectrum resembles the $1/f$ noise observed in isotopically purified silicon qubits.
Transport measurements of CVD graphene nanoribbons

北田孝仁, 阿部峰也, 瀬尾瑞樹, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　75　(1)　2020

ISSN： 2189-079X
Formation of quantum dots of CVD graphene nanoribbons

北田孝仁, 阿部峰也, 篠崎基矢, 瀬尾瑞樹, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　75　(2)　2020

ISSN： 2189-079X
Noise analysis of high-frequency measurements in quantum dots

篠崎基矢, 武藤由依, 北田孝仁, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, 伊藤匠, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　75　(2)　2020

ISSN： 2189-079X
Noise dependence of the charge state estimation in quantum dots by Bayesian estimation

武藤由依, 篠崎基矢, 北田孝仁, 永安修也, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LI Sen, 伊藤匠, 樽茶清悟, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　75　(2)　2020

ISSN： 2189-079X
Charge state estimation of quantum dots by machine learning

中曽拓, 篠崎基矢, 相澤拓海, 北田孝仁, 武藤由依, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, 伊藤匠, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 兼村厚範, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　75　(2)　2020

ISSN： 2189-079X
Quantum nondemolition measurement of an electron spin qubit

Takashi Nakajima, Akito Noiri, Jun Yoneda, Matthieu R. Delbecq, Peter Stano, Tomohiro Otsuka, Kenta Takeda, Shinichi Amaha, Giles Allison, Kento Kawasaki, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

2019/04/25

DOI： 10.1038/s41565-019-0426-x 　

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Measurement of quantum systems inevitably involves disturbance in various forms. Within the limits imposed by quantum mechanics, however, one can design an "ideal" projective measurement that does not introduce a back action on the measured observable, known as a quantum nondemolition (QND) measurement. Here we demonstrate an all-electrical QND measurement of a single electron spin in a gate-defined quantum dot via an exchange-coupled ancilla qubit. The ancilla qubit, encoded in the singlet-triplet two-electron subspace, is entangled with the single spin and subsequently read out in a single shot projective measurement at a rate two orders of magnitude faster than the spin relaxation. The QND nature of the measurement protocol is evidenced by observing a monotonic increase of the readout fidelity over one hundred repetitive measurements against arbitrary input states. We extract information from the measurement record using the method of optimal inference, which is tolerant to the presence of the relaxation and dephasing. The QND measurement allows us to observe spontaneous spin flips (quantum jumps) in an isolated system with small disturbance. Combined with the high-fidelity control of spin qubits, these results pave the way for various measurement-based quantum state manipulations including quantum error correction protocols.
量子デバイスの高周波測定技術

大塚朋廣

日本物理学会講演概要集(CD-ROM)　74　(1)　2019

ISSN： 2189-079X
GaN FETにおける量子ドット形成

阿部峰也, 北田孝仁, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会講演概要集(CD-ROM)　74　(2)　2019

ISSN： 2189-079X
電子スピンの量子テレポーテーションに向けた実験

小嶋洋平, 小嶋洋平, 中島峻, 野入亮人, 米田淳, 大塚朋廣, 大塚朋廣, 武田健太, LI Sen, BARTLETT Stephen D., LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　74　(1)　2019

ISSN： 2189-079X
微小磁石ESRに用いる局所磁場パラメータの解析

伊藤匠, 大塚朋廣, 中島峻, DELBECQ Matthieu, 天羽真一, 米田淳, 武田健太, 野入亮人, ALLISON Giles, LUDWIG Arne, WIECK Andreas, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　74　(1)　2019

ISSN： 2189-079X
フィードバック制御による電子スピン量子ビットの操作忠実度の向上

野入亮人, 中島峻, 川崎賢人, 米田淳, STANO Peter, 天羽真一, 大塚朋廣, 武田健太, DELBECQ Matthieu R., ALLISON Giles, LUDWIG Arne, WIECK Andreas D., LOSS Daniel, LOSS Daniel, 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　74　(1)　2019

ISSN： 2189-079X
4重量子ドットにおける4電子スピン状態測定法の開発

伊藤匠, 大塚朋廣, 中島峻, DELBECQ Matthieu, 天羽真一, 米田淳, 武田健太, 野入亮人, ALLISON Giles, LUDWIG Arne, WIECK Andreas D., 樽茶清悟

日本物理学会講演概要集(CD-ROM)　74　(2)　2019

ISSN： 2189-079X
Difference in charge and spin dynamics in a quantum dot-lead coupled system

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2018/08/15

DOI： 10.1103/PhysRevB.99.085402 　

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We analyze time evolution of charge and spin states in a quantum dot coupled to an electric reservoir. Utilizing high-speed single-electron detection, we focus on dynamics induced by the first-order tunneling. We find that there is a difference between the spin and the charge relaxation: the former appears slower than the latter. The difference depends on the Fermi occupation factor and the spin relaxation becomes slower when the energy level of the quantum dot is lowered. We explain this behavior by a theory which includes the first-order tunneling processes. We conduct detailed comparison of the experiment and the theory with changing the energy of the quantum dot levels, and the theory can reproduce the experimental results.
Four single-spin Rabi oscillations in a quadruple quantum dot

Takumi Ito, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Akito Noiri, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2018/05/16

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Scaling up qubits is a necessary step to realize useful systems of quantum computation. Here we demonstrate coherent manipulations of four individual electron spins using a micro-magnet method in a quadruple quantum dot - the largest number of dots used for the single spin control in multiple quantum dots. We observe Rabi oscillations and electron spin resonance (ESR) for each dot and evaluate the spin-electric coupling of the four dots, and finally discuss practical approaches to independently address single spin control in multiple quantum dot systems containing even more quantum dots.
シリコン量子ドットにおける2スピン同時検出

米田淳, 武田健太, 野入亮人, 中島峻, 大塚朋廣, LI Sen, 小寺哲夫, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　73　(1)　2018

ISSN： 2189-079X
電子スピンの量子テレポーテーションに向けた実験スキーム

小嶋洋平, 小嶋洋平, 中島峻, 野入亮人, 米田淳, 大塚朋廣, 武田健太, 伊藤匠, 伊藤匠, BARTLETT Stephen D., LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　73　(1)　2018

ISSN： 2189-079X
ベイズ推定を用いた量子ドット電荷計の信号解析

大塚朋廣, 永安修也, 中島峻, DELBECQ Matthieu R., 米田淳, 武田健太, 野入亮人, LI Sen, 伊藤匠, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　73　(1)　2018

ISSN： 2189-079X
異種スピン量子ビット間の制御位相ゲート

野入亮人, 中島峻, 米田淳, DELBECQ Matthieu R., STANO Peter, 大塚朋廣, 武田健太, 天羽真一, ALLISON Giles, 川崎賢人, LUDWIG Arne, WIECK Andreas D., LOSS Daniel, LOSS Daniel, 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　73　(1)　2018

ISSN： 2189-079X
同位体制御Si/SiGe単一電子スピンの1/f電荷揺らぎによる位相雑音

米田淳, 武田健太, 大塚朋廣, 中島峻, DELBECQ Matthieu R, ALLISON Giles, 本田拓夢, 小寺哲夫, 小田俊理, 星裕介, 宇佐美徳隆, 伊藤公平, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(2)　ROMBUNNO.21pB31‐4　2017/09/25

ISSN： 2189-079X
同位体制御Si/SiGe電子スピン量子ビットの高速量子操作忠実度

米田淳, 武田健太, 大塚朋廣, 中島峻, DELBECQ Matthieu R, ALLISON Giles, 本田拓夢, 小寺哲夫, 小田俊理, 星裕介, 宇佐美徳隆, 伊藤公平, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(1)　ROMBUNNO.17pA21‐7　2017/03/21

ISSN： 2189-079X
Robust Single-Shot Spin Measurement with 99.5% Fidelity in a Quantum Dot Array

Takashi Nakajima, Matthieu R. Delbecq, Tomohiro Otsuka, Peter Stano, Shinichi Amaha, Jun Yoneda, Akito Noiri, Kento Kawasaki, Kenta Takeda, Giles Allison, Arne Ludwig, Andreas D. Wieck, Daniel Loss, Seigo Tarucha

2017/01/13

DOI： 10.1103/PhysRevLett.119.017701 　

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We demonstrate a new method for projective single-shot measurement of two electron spin states (singlet versus triplet) in an array of gate-defined lateral quantum dots in GaAs. The measurement has very high fidelity and is robust with respect to electric and magnetic fluctuations in the environment. It exploits a long-lived metastable charge state, which increases both the contrast and the duration of the charge signal distinguishing the two measurement outcomes. This method allows us to evaluate the charge measurement error and the spin-to-charge conversion error separately. We specify conditions under which this method can be used, and project its general applicability to scalable quantum dot arrays in GaAs or silicon.
局所的な電子状態の高速な制御,検出手法の研究

大塚朋廣

日本物理学会講演概要集(CD-ROM)　72　(1)　2017

ISSN： 2189-079X
異種スピン量子ビット間の制御NOTゲート II

中島峻, 野入亮人, 米田淳, 大塚朋廣, 武田健太, DELBECQ Matthieu R., 川崎賢人, ALLISON Giles, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(1)　2017

ISSN： 2189-079X
異種スピン量子ビット間の制御NOTゲート I

野入亮人, 中島峻, 米田淳, 大塚朋廣, 武田健太, DELBECQ Matthieu R., 川崎賢人, ALLISON Giles, LUDWIG Arne, WIECK Andreas D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(1)　2017

ISSN： 2189-079X
フィードバック制御による電子スピン位相緩和の抑制 II

野入亮人, 川崎賢人, 中島峻, 米田淳, STANO P., 大塚朋廣, 武田健太, DELBECQ Matthieu R., ALLISON Giles, LUDWIG Arne, WIECK Andreas D., LOSS D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(2)　2017

ISSN： 2189-079X
フィードバック制御による電子スピン位相緩和の抑制 I

中島峻, 川崎賢人, 野入亮人, 米田淳, STANO P., 大塚朋廣, 武田健太, DELBECQ Matthieu R., ALLISON Giles, LUDWIG Arne, WIECK Andreas D., LOSS D., 樽茶清悟, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(2)　2017

ISSN： 2189-079X
4重量子ドットにおける4スピンの独立なRabi振動の観測

伊藤匠, 大塚朋廣, 中島峻, DELBECQ Matthieu, 天羽真一, 米田淳, 武田健太, 野入亮人, ALLISON Giles, LUDWIG Arne, WIECK Andreas D., 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(1)　2017

ISSN： 2189-079X
量子ドット-電極結合系における電荷・スピンダイナミクス

大塚朋廣, 中島峻, DELBECQ Matthieu R., STANO Peter, 天羽真一, 米田淳, 武田健太, ALLISON Giles, 野入亮人, 伊藤匠, LOSS Daniel, LUDWIG Arne, WIECK Andreas D., 樽茶清悟

日本物理学会講演概要集(CD-ROM)　72　(2)　2017

ISSN： 2189-079X
Fast probe of local electronic states in nanostructures utilizing a single-lead quantum dot

Tomohiro Otsuka, Shinichi Amaha, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Retsu Sugawara, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2016/10/07

DOI： 10.1038/srep14616 　

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Transport measurements are powerful tools to probe electronic properties of solid-state materials. To access properties of local electronic states in nanostructures, such as local density of states, electronic distribution and so on, micro-probes utilizing artificial nanostructures have been invented to perform measurements in addition to those with conventional macroscopic electronic reservoirs. Here we demonstrate a new kind of micro-probe: a fast single-lead quantum dot probe, which utilizes a quantum dot coupled only to the target structure through a tunneling barrier and fast charge readout by RF reflectometry. The probe can directly access the local electronic states with wide bandwidth. The probe can also access more electronic states, not just those around the Fermi level, and the operations are robust against bias voltages and temperatures.
同位体制御されたSi/SiGe量子ドットにおける単一電子スピン共鳴

米田淳, 武田健太, 大塚朋廣, 中島峻, DELBECQ Matthieu R, ALLISON Giles, 本田拓夢, 小寺哲夫, 小田俊理, 星裕介, 宇佐美徳隆, 伊藤公平, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　71　(2)　ROMBUNNO.15aAB‐11　2016/09/23

ISSN： 2189-079X
Si/SiGe多重量子ドットの形成と電荷状態測定

大塚朋廣, 武田健太, 米田淳, 本田拓夢, DELBECQ Matthieu, ALLISON Giles, MARX Marian, 中島峻, 小寺哲夫, 小田俊理, 星裕介, 宇佐美徳隆, 伊藤公平, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　71　(2)　ROMBUNNO.15aAB‐10　2016/09/23

ISSN： 2189-079X
Tunneling induced spin dynamics in a quantum dot-lead hybrid system

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Peter Stano, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2016/08/27

DOI： 10.1038/s41598-017-12217-6 　

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Semiconductor quantum dots (QDs) offer a platform to explore the physics of quantum electronics including spins. Electron spins in QDs are considered good candidates for quantum bits in quantum information processing, and spin control and readout have been established down to a single electron level. We use these techniques to explore spin dynamics in a hybrid system, namely a QD coupled to a two dimensional electronic reservoir. The proximity of the lead results in relaxation dynamics of both charge and spin, the mechanism of which is revealed by comparing the charge and spin signal. For example, higher order charge tunneling events can be monitored by observing the spin. We expect these results to stimulate further exploration of spin dynamics in QD-lead hybrid systems and expand the possibilities for controlled spin manipulations.
Detection and control of charge states in a quintuple quantum dot

Takumi Ito, Tomohiro Otsuka, Shinichi Amaha, Matthieu R. Delbecq, Takashi Nakajima, Jun Yoneda, Kenta Takeda, Giles Allison, Akito Noiri, Kento Kawasaki, Seigo Tarucha

2016/04/15

DOI： 10.1038/srep39113 　

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A semiconductor quintuple quantum dot with two charge sensors and an additional contact to the center dot from an electron reservoir is fabricated to demonstrate the concept of scalable architecture. This design enables formation of the five dots as confirmed by measurements of the charge states of the three nearest dots to the respective charge sensor. The gate performance of the measured stability diagram is well reproduced by a capacitance model.These results provide an important step towards realizing controllable large scale multiple quantum dot systems.
Coherent electron-spin-resonance manipulation of three individual spins in a triple quantum dot

Akito Noiri, Jun Yoneda, Takashi Nakajima, Tomohiro Otsuka, Matthiew R. Delbecq, Kenta Takeda, Shinichi Amaha, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2016/04/13

DOI： 10.1063/1.4945592 　

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Quantum dot arrays provide a promising platform for quantum information processing. For universal quantum simulation and computation, one central issue is to demonstrate the exhaustive controllability of quantum states. Here, we report the addressable manipulation of three single electron spins in a triple quantum dot using a technique combining electron-spin-resonance and a micro-magnet. The micro-magnet makes the local Zeeman field difference between neighboring spins much larger than the nuclear field fluctuation, which ensures the addressable driving of electron-spin-resonance by shifting the resonance condition for each spin. We observe distinct coherent Rabi oscillations for three spins in a semiconductor triple quantum dot with up to 25 MHz spin rotation frequencies. This individual manipulation over three spins enables us to arbitrarily change the magnetic spin quantum number of the three spin system, and thus to operate a triple-dot device as a three-qubit system in combination with the existing technique of exchange operations among three spins.
Coherent transfer of electron spin correlations assisted by dephasing noise

Takashi Nakajima, Matthieu R. Delbecq, Tomohiro Otsuka, Shinichi Amaha, Jun Yoneda, Akito Noiri, Kenta Takeda, Giles Allison, Arne Ludwig, Andreas D. Wieck, Xuedong Hu, Franco Nori, Seigo Tarucha

2016/04/08

DOI： 10.1038/s41467-018-04544-7 　

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Quantum coherence of superposed states, especially of entangled states, is indispensable for many quantum technologies. However, it is vulnerable to environmental noises, posing a fundamental challenge in solid-state systems including spin qubits. Here we show a scheme of entanglement engineering where pure dephasing assists the generation of quantum entanglement at distant sites in a chain of electron spins confined in semiconductor quantum dots. One party of an entangled spin pair, prepared at a single site, is transferred to the next site and then adiabatically swapped with a third spin using a transition across a multi-level avoided crossing. This process is accelerated by the noise-induced dephasing through a variant of the quantum Zeno effect, without sacrificing the coherence of the entangled state. Our finding brings insight into the spin dynamics in open quantum systems coupled to noisy environments, opening an avenue to quantum state manipulation utilizing decoherence effects.
Single-electron Spin Resonance in a Quadruple Quantum Dot

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Takumi Ito, Retsu Sugawara, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2015/10/09

DOI： 10.1038/srep31820 　

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Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of the electron spin resonance is possible.
領域4「III-V族半導体によるトポロジカル絶縁体の実現〜InAs/GaSb量子スピンホール系のエッジ伝導〜」(企画講演,第70回年次大会(2015年)招待・企画・チュートリアル講演の報告,学会報告)

大塚朋廣

日本物理學會誌　70　(8)　638-638　2015/08/05
Publisher: 一般社団法人日本物理学会
ISSN： 0029-0181
Robust micro-magnet design for fast electrical manipulations of single spins in quantum dots

Jun Yoneda, Tomohiro Otsuka, Tatsuki Takakura, Michel Pioro-Ladrière, Roland Brunner, Hong Lu, Takashi Nakajima, Toshiaki Obata, Akito Noiri, Christopher J. Palmstrøm, Arthur C. Gossard, Seigo Tarucha

2015/07/07

DOI： 10.7567/APEX.8.084401 　

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Tailoring spin coupling to electric fields is central to spintronics and spin-based quantum information processing. We present an optimal micromagnet design that produces appropriate stray magnetic fields to mediate fast electrical spin manipulations in nanodevices. We quantify the practical requirements for spatial field inhomogeneity and tolerance for misalignment with spins, and propose a design scheme to improve the spin-rotation frequency (to exceed 50MHz in GaAs nanostructures). We then validate our design by experiments in separate devices. Our results will open a route to rapidly control solid-state electron spins with limited lifetimes and to study coherent spin dynamics in solids.
電極閉じ込め型シリコンMOS量子ドットの作製と評価

米田淳, 本田拓夢, 武田健太, MARX Marian, 大塚朋廣, 中島峻, DELBECQ Matthieu, 天羽真一, ALLISON Giles, 小寺哲夫, 小田俊理, 樽茶清悟

日本物理学会講演概要集(CD-ROM)　70　(2)　2015

ISSN： 2189-079X
8pAV-4 Experimental Study of Spin Qubits in Triple Quantum Dot II

Nakajima Takashi, Otsuka Tomohiro, Delbecq Matthieu, Amaha Shinichi, Yoneda Jun, Noiri Akito, Takeda Kenta, Sugawara Retsu, Tarucha Seigo

Meeting abstracts of the Physical Society of Japan　69　(2)　478-478　2014/08/22
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
8pAV-3 Experimental Study of Spin Qubits in Triple Quantum Dot I

Otsuka T., Nakajima T., Delbecq M., Amaha S., Yoneda J., Noiri A., Takeda K., Sugawara R., Tarucha S.

Meeting abstracts of the Physical Society of Japan　69　(2)　478-478　2014/08/22
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
8pAV-5 Electrically driven single-electron spin resonance in a Si/SiGe double quantum dot with a micromagnet

Takeda K., Kamioka J., Obata T., Otsuka T., Nakajima T., Delbecq M., Amaha S., Yoneda J., Noiri A., Sugawara R., Kodera T., Oda S., Tarucha S.

Meeting abstracts of the Physical Society of Japan　69　(2)　478-478　2014/08/22
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Single-spin manipulation in a double quantum dot in the field of a micromagnet

Stefano Chesi, Ying-Dan Wang, Jun Yoneda, Tomohiro Otsuka, Seigo Tarucha, Daniel Loss

2014/05/29

DOI： 10.1103/PhysRevB.90.235311 　

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The manipulation of single spins in double quantum dots by making use of the exchange interaction and a highly inhomogeneous magnetic field was discussed in [W. A. Coish and D. Loss, Phys. Rev. B 75, 161302 (2007)]. However, such large inhomogeneity is difficult to achieve through the slanting field of a micromagnet in current designs of lateral double dots. Therefore, we examine an analogous spin manipulation scheme directly applicable to realistic GaAs double dot setups. We estimate that typical gate times, realized at the singlet-triplet anticrossing induced by the inhomogeneous micromagnet field, can be a few nanoseconds. We discuss the optimization of initialization, read-out, and single-spin gates through suitable choices of detuning pulses and an improved geometry. We also examine the effect of nuclear dephasing and charge noise. The latter induces fluctuations of both detuning and tunneling amplitude. Our results suggest that this scheme is a promising approach for the realization of fast single-spin operations.
Single to quadruple quantum dots with tunable tunnel couplings

Tatsuki Takakura, Akito Noiri, Toshiaki Obata, Tomohiro Otsuka, Jun Yoneda, Katsuharu Yoshida, Seigo Tarucha

2014/01/10

DOI： 10.1063/1.4869108 　

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We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by gate geometry. For the triple and quadruple dots we study gate-tunable inter-dot tunnel couplings. Particularly for the triple dot we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot device has gate performance relevant for implementing spin-based four-qubit systems with controllable exchange couplings.
Single to quadruple quantum dots with tunable tunnel couplings

Tatsuki Takakura, Akito Noiri, Toshiaki Obata, Tomohiro Otsuka, Jun Yoneda, Katsuharu Yoshida, Seigo Tarucha

2014/01/10

DOI： 10.1063/1.4869108 　

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We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by gate geometry. For the triple and quadruple dots we study gate-tunable inter-dot tunnel couplings. Particularly for the triple dot we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot device has gate performance relevant for implementing spin-based four-qubit systems with controllable exchange couplings.
三重量子ドットを用いたスピン・キュービット実験 I

大塚朋廣, 中島峻, DELBECQ M., 天羽真一, 米田淳, 野入亮人, 武田健太, 菅原烈, 樽茶清悟

日本物理学会講演概要集　69　(2)　2014

ISSN： 1342-8349
Pauli spin blockade in a three-terminal triple quantum dot

Noiri A., Takakura T., Obata T., Otsuka T., Nakajima T., Yoneda J., Tarucha S.

Meeting abstracts of the Physical Society of Japan　68　(2)　634-634　2013/08/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Phase Gates Of A Single Electron Spin Qubit

Yoneda J., Otsuka T., Nakajima T., Takakura T., Obata T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　68　(2)　635-635　2013/08/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Probing energy relaxation in quantum Hall edge states utilizing quantum point contacts

Otsuka T., Sugihara Y., Yoneda J., Nakajima T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　68　(2)　611-611　2013/08/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Measurement of energy relaxation in quantum Hall edge states utilizing quantum point contacts

Tomohiro Otsuka, Yuuki Sugihara, Jun Yoneda, Takashi Nakajima, Seigo Tarucha

2013/04/29

DOI： 10.7566/JPSJ.83.014710 　

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We demonstrated a method to probe local electronic states and energy relaxation in quantum Hall edge states utilizing quantum point contacts. We evaluated relaxation lengths in two cases; first, with electron tunneling, and second, only with energy exchange without tunneling between edge states. The results were consistent with previous experiments and validated our method with quantum point contacts. We applied this method to measure the energy relaxation length around a hotspot in quantum Hall regimes and revealed the possible short-distance relaxation process to be the relaxation due to energy exchange between edge states without electron tunneling.
Measurement of energy relaxation in quantum Hall edge states utilizing quantum point contacts

Tomohiro Otsuka, Yuuki Sugihara, Jun Yoneda, Takashi Nakajima, Seigo Tarucha

2013/04/29

DOI： 10.7566/JPSJ.83.014710 　

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We demonstrated a method to probe local electronic states and energy relaxation in quantum Hall edge states utilizing quantum point contacts. We evaluated relaxation lengths in two cases; first, with electron tunneling, and second, only with energy exchange without tunneling between edge states. The results were consistent with previous experiments and validated our method with quantum point contacts. We applied this method to measure the energy relaxation length around a hotspot in quantum Hall regimes and revealed the possible short-distance relaxation process to be the relaxation due to energy exchange between edge states without electron tunneling.
29aXQ-4 Time-resolved Measurement of Fast Rabi Oscillation of Single-electron Spin Rresonance

Yoneda J., Otsuka T., Nakajima T., Takakura T., Obata T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　68　(1)　784-784　2013/03/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
29aXQ-11 Quadruple Quantum Dot with Tunable Interdot Tunnel Couplings

Noiri A., Takakura T., Obata T., Otsuka T., Yoneda J., Yoshida K., Tarucha S.

Meeting abstracts of the Physical Society of Japan　68　(1)　786-786　2013/03/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
26aXQ-6 Gate-Bias Dependence of Conductance Fluctuations in GaAs Quantum Point Contacts

Nakajima Takashi, Otsuka Tomohiro, Yoneda Jun, Noiri Akito, Tarucha Seigo

Meeting abstracts of the Physical Society of Japan　68　(1)　743-743　2013/03/26
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Detection of spin polarization utilizing singlet and triplet states in a single-lead quantum dot

Tomohiro Otsuka, Yuuki Sugihara, Jun Yoneda, Shingo Katsumoto, Seigo Tarucha

2012/06/26

DOI： 10.1103/PhysRevB.86.081308 　

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We propose and demonstrate a new method to probe local spin polarization in semiconductor micro devices at low and zero magnetic fields. By connecting a single-lead quantum dot to a semiconductor micro device and monitoring electron tunneling into singlet and triplet states in the dot, we can detect the local spin polarization formed in the target device. We confirm the validity of this detection scheme utilizing spin split quantum Hall edge states. We also observe non-zero local spin polarization at the device edge in low magnetic fields, which is not detectable with conventional macroscopic probes.
26pCE-8 Electron spin resonance in a double quantum dot with large Zeeman field difference

Yoneda J., Otsuka T., Takakura T., Obata T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　67　(1)　744-744　2012/03/05
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
26pCE-7 Detection of spin polarization utilizing two-electron states in a single-lead quantum dot

Otsuka T., Sugihara Y., Yoneda J., Obata T., Katsumoto S., Tarucha S.

Meeting abstracts of the Physical Society of Japan　67　(1)　744-744　2012/03/05
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
24aTR-6 Control of local Zeeman energy difference between neighboring quantum dots by micro-magnet design

Yoneda J., Otsuka T., Takakura T., Obata T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　66　(2)　705-705　2011/08/24
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
28pHD-2 Energy Level Spectroscopy of a Quantum Dot with a Side-coupled Satellite Dot

Kuwabara Yuki, Kim Sunwoo, Otsuka Tomohiro, Iye Yasuhiro, Katsumoto Shingo

Meeting abstracts of the Physical Society of Japan　66　(1)　729-729　2011/03/03
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
28aHD-3 Double-quantum-dot devices with a large difference in local magnetic field for fast spin manipulation

Yoneda J., Otsuka T., Takakura T., Obata T., Tarucha S.

Meeting abstracts of the Physical Society of Japan　66　(1)　724-724　2011/03/03
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Si/SiGe量子ドットにおけるショットキーゲート電極に対する考察

武田健太, 小幡利顕, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会講演概要集　66　(1)　2011

ISSN： 1342-8349
Si/SiGe量子ドット作製に向けたPdトップゲート動作点の低電圧化

福岡佑二, 小寺哲夫, 小寺哲夫, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 樽茶清悟, 小田俊理

応用物理学関係連合講演会講演予稿集(CD-ROM)　58th　2011
Si/SiGe量子ドット構造のシミュレーションと作製

福岡佑二, 小寺哲夫, 小寺哲夫, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 樽茶清悟, 小田俊理

応用物理学会学術講演会講演予稿集(CD-ROM)　72nd　2011
Si/SiGe系2DEGのPdショットキーゲート制御による結合量子ドットの作製

福岡佑二, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 小田俊理

応用物理学会学術講演会講演予稿集(CD-ROM)　71st　2010
SiGeヘテロ構造上のMOS電気ゲートを使った横型のドットの作製<英文title>Lateral dot fabrication by using a MOS electric gate on SiGe hetero structure.

小幡利顕, 申潤錫, ロランドブルナ, 武田健太, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会講演概要集　65　(2)　2010

ISSN： 1342-8349
PdショットキーゲートによるSi/SiGe量子ドットの作製とその評価

武田健太, 小幡利顕, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会講演概要集　65　(2)　2010

ISSN： 1342-8349
Probing local electronic states in the quantum Hall regime with a side coupled quantum dot

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

2009/12/24

DOI： 10.1103/PhysRevB.81.245302 　

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We demonstrate a new method for locally probing the edge states in the quantum Hall regime utilizing a side coupled quantum dot positioned at an edge of a Hall bar. By measuring the tunneling of electrons from the edge states into the dot, we acquire information on the local electrochemical potential and electron temperature of the edge states. Furthermore, this method allows us to observe the spatial modulation of the electrostatic potential at the edge state due to many-body screening effect.
Probing local electronic states in the quantum Hall regime with a side coupled quantum dot

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

2009/12/24

DOI： 10.1103/PhysRevB.81.245302 　

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We demonstrate a new method for locally probing the edge states in the quantum Hall regime utilizing a side coupled quantum dot positioned at an edge of a Hall bar. By measuring the tunneling of electrons from the edge states into the dot, we acquire information on the local electrochemical potential and electron temperature of the edge states. Furthermore, this method allows us to observe the spatial modulation of the electrostatic potential at the edge state due to many-body screening effect.
26aXG-11 Probing quantum Hall states with a side coupled quantum dot

Otsuka T., Abe E., Iye Y., Katsumoto S.

Meeting abstracts of the Physical Society of Japan　64　(2)　595-595　2009/08/18
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
30pTX-6 Detection of Spin Polarization with a Side Coupled Quantum Dot

Otsuka T., Abe E., Iye Y., Katsumoto S.

Meeting abstracts of the Physical Society of Japan　64　(1)　714-714　2009/03/03
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Detection of spin polarization with a side coupled quantum dot

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

2009/02/25

DOI： 10.1103/PhysRevB.79.195313 　

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We propose realistic methods to detect local spin polarization, which utilize a quantum dot side coupled to the target system. By choosing appropriate states in the dot, we can put spin selectivity to the dot and detect spins in the target with small disturbance. We also present an experiment which realizes one of the proposed spin detection schemes in magnetic fields.
Excited-state spectroscopy on a quantum dot side-coupled to a quantum wire

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

2008/07/23

DOI： 10.1063/1.2987424 　

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We report excited-state spectroscopy on a quantum dot side-coupled to a quantum wire with accurate energy estimation. Our method utilizes periodic voltage pulses on the dot, and the energy calibration is performed with reference to the bias voltage across the wire. We demonstrate the observation of the orbital excited state and the Zeeman splitting in a single dot.
Excited-state spectroscopy on a quantum dot side-coupled to a quantum wire

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

2008/07/23

DOI： 10.1063/1.2987424 　

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We report excited-state spectroscopy on a quantum dot side-coupled to a quantum wire with accurate energy estimation. Our method utilizes periodic voltage pulses on the dot, and the energy calibration is performed with reference to the bias voltage across the wire. We demonstrate the observation of the orbital excited state and the Zeeman splitting in a single dot.
横結合型量子ドットにおける励起状態の観測

大塚朋廣, 阿部英介, 家泰弘, 勝本信吾

日本物理学会講演概要集　63　(2)　2008

ISSN： 1342-8349
20pYF-4 Excited-State Spectroscopy on a Side-Coupled Quantum Dot

Otsuka T., Abe E., Iye Y., Katsumoto S.

Meeting Abstracts of the Physical Society of Japan　63　(0)　593-593　2008
Publisher: The Physical Society of Japan
DOI： 10.11316/jpsgaiyo.63.2.4.0_593_3 　

ISSN： 1342-8349
24aTH-8 Coulomb Interaction in a Side-Coupled Quantum Dot

Otsuka T., Abe E., Katsumoto S., Iye Y.

Meeting abstracts of the Physical Society of Japan　62　(2)　713-713　2007/08/21
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
20pRC-12 Non-Local Control of the Kondo Effect

Otsuka T., Katsumoto S., Iye Y.

Meeting abstracts of the Physical Society of Japan　62　(1)　685-685　2007/02/28
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Fano Effect in a Few-Electron Quantum Dot

Tomohiro Otsuka, Eisuke Abe, Shingo Katsumoto, Yasuhiro Iye, Gyong Luck Khym, Kicheon Kang

2007/01/01

DOI： 10.1143/JPSJ.76.084706 　

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We have studied the Fano effect in a few-electron quantum dot side-coupled to a quantum wire. The conductance of the wire, which shows an ordinal staircase-like quantization without the dot, is modified through the interference (the Fano effect) and the charging effects. These effects are utilized to verify the exhaustion of electrons in the dot. The "addition energy spectrum" of the dot shows a shell structure, indicating that the electron confinement potential is fairly circular. A rapid sign inversion of the Fano parameter on the first conductance plateau with the change of the wire gate voltage has been observed, and explained by introducing a finite width of dot-wire coupling.
29pXB-1 On Breaking of "Phase Rigidity" in Transport through a Two-Terminal AB Ring

Katsumoto Shingo, Ohtsuka Tomohiro, Aharony Amnon, Entin-Wohlman Ora

Meeting abstracts of the Physical Society of Japan　61　(1)　695-695　2006/03/04
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
29pXB-2 Quantum transport through a quantum wire with a side-coupled quantum dot

Otsuka T., Katsumoto S., Iye Y., Khym G.L., Kang Kicheon

Meeting abstracts of the Physical Society of Japan　61　(1)　695-695　2006/03/04
Publisher: The Physical Society of Japan (JPS)
ISSN： 1342-8349
Breakdown of `phase rigidity' and variations of the Fano effect in closed Aharonov-Bohm interferometers

Amnon Aharony, Ora Entin-Wohlman, Tomohiro Otsuka, Shingo Katsumoto, Hisashi Aikawa, Kensuke Kobayashi

2005/12/16

DOI： 10.1103/PhysRevB.73.195329 　

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Although the conductance of a closed Aharonov-Bohm interferometer, with a quantum dot on one branch, obeys the Onsager symmetry under magnetic field reversal, it needs not be a periodic function of this field: the conductance maxima move with both the field and the gate voltage on the dot, in an apparent breakdown of `phase rigidity'. These experimental findings are explained theoretically as resulting from multiple electronic paths around the interferometer ring. Data containing several Coulomb blockade peaks, whose shapes change with the magnetic flux, are fitted to a simple model, in which each resonant level on the dot couples to a different path around the ring.

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Books and Other Publications 1

量子ドット技術の最前線

荒川泰彦監修

エヌ・ティー・エス　2025/09

ISBN: 9784860439767

Presentations 299

High-Frequency Quantum Devices with Graphene and 2D Materials towards Quantum Information Processing Invited

Tomohiro Otsuka

Graphene India 2026　2026/03/10
Semiconductor Quantum Technologies Using Artificial Nanostructures and Emerging Materials

Hiroto Ogura, Yuto Tsukidate, Zhuoqun Li, Azusa Utsumi, Tomohiro Otsuka, Toshiaki Kato

The 70th Commemorative Fullerenes-Nanotubes-Graphene General Symposium　2026/03/05
New Materials and Informatics Approaches for Semiconductor Quantum Technologies Invited

Tomohiro Otsuka

The 29th SANKEN International Symposium　2026/01/08
New materials and techniques for semiconductor quantum technologies

Tomohiro Otsuka

Seminar at University of Washington QuantumX　2025/12/19
2025年度低温技術夏合宿ー77K小型冷凍機を作ろうー

齊藤雅裕, 大塚朋廣, 木原孟士

2025年度秋季低温工学・超電導学会研究発表会　2025/12/09
次世代量子情報処理に向けた半導体量子デバイスと新材料に関する研究 Invited

大塚朋廣

石田實記念財団研究奨励賞贈呈式・研究発表会　2025/11/07
Development of MoS2 quantum devices with a micro-graphite back gate

Yuta Kera, Akitomi Shirachi, Motoya Shinozaki, Shunsuke Yashima, Kosuke Noro, Takeshi Kumasaka, Azusa Utsumi, Takashi Taniguchi, Kenji Watanabe, Tomohiro Otsuka

International Symposium MSSp2025　2025/11/05
Formation of quantum dots in graphene nano islands

Takumi Seo, Motoya Shinozaki, Akiko Tada, Yuta Kera, Shunsuke Yashima, Kosuke Noro, Takeshi Kumasaka, Azusa Utsumi, Takashi Matsumoto, Yoshiyuki Kobayashi, Tomohiro Otsuka

International Symposium MSSp2025　2025/11/05
Observation of ZnO Double Quantum Dots in Few-Electron Regime

Kosuke Noro, Motoya Shinozaki, Yusuke Kozuka, Kazuma Matsumura, Yoshihiro Fujiwara, Takeshi Kumasaka, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

International Symposium MSSp2025　2025/11/05
On-Board Calibrated Cryogenic RF Characterization of SrTiO₃ Varactors for Quantum Device Applications

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Hisashi Inoue, Kenta Itoh, Yusuke Kozuka, Takanobu Watanabe, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

International Symposium MSSp2025　2025/11/05
Direct fabrication of graphene/hBN-based superconductor junctions by plasma-enhanced chemical vapor deposition

Zhuoqun Li, Yuto Tsukisate, Hiroto Ogura, Azusa Utsumi, Tomohiro Otsuka, Toshiaki Kato

The 16th International Conference on Recent Progress in Graphene and 2D Materials Research　2025/11/05
Efficient Fabrication of Graphene-Based Josephson Junctions for Large-Scale Integrated Quantum Devices

Hiroto Ogura, Yuto Tsukidate, Zhuoqun Li, Azusa Utsumi, Tomohiro Otsuka, Toshiaki Kato

The 16th International Conference on Recent Progress in Graphene and 2D Materials Research　2025/11/04
新量子材料の物性解明と革新的半導体量子技術への展開

大塚朋廣

JST創発森パネル2025秋の創発の場　2025/11/05
Cryogenic On-Board Calibrated RF Measurement for Characterizing SrTiO3-Based Capacitors

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Hisashi Inoue, Kenta Itoh, Yusuke Kozuka, Takanobu Watanabe, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

International Conference on Hybrid Quantum Systems and Nanotechnologies 2025　2025/10/27
量子コンピューター Invited

大塚朋廣

応用物理学会第24回スピントロニクス入門セミナー　2025/10/22
Integrated Machine Learning Approach for Defining Virtual Gates and Identifying the Single-Electron Regime in Quantum Dots

Yui Muto, Michael R. Zielewski, Motoya Shinozaki, Kosuke Noro, Tomohiro Otsuka

The 14th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2025/09/29
Cryogenic RF Characterization of SrTiO₃ Varactors with Integrated On-Board Calibration

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Hisashi Inoue, Kenta Itoh, Yusuke Kozuka, Takanobu Watanabe, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

The 14th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2025/09/29
Microwave varactor using Pt/SrTiO3 Schottky junctions

Kenta Itoh, Akitomi Shirachi, Motoya Shinozaki, Shoichi Sato, Takeshi Kumasa-ka, Tomohiro Otsuka, Takanobu Watanabe, Yusuke Kozuka

31st International Workshop on Oxide Electronics　2025/09/29
Electrostatically defined quantum dots in ZnO heterostructures

Kosuke Noro, Motoya Shinozaki, Yusuke Kozuka, Kazuma Matsumura, Yoshihiro Fujiwara, Takeshi Kumasaka, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

31st International Workshop on Oxide Electronics　2025/09/29
Few-Electron ZnO Double Quantum Dots Characterized via RF Reflectometry

Kosuke Noro, Motoya Shinozaki, Yusuke Kozuka, Kazuma Matsumura, Yoshihiro Fujiwara, Takeshi Kumasaka, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

The 14th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2025/09/29
Control of Contact Interface Quality for Efficient Fabrication of Graphene-Based Josephson Junctions

Hiroto Ogura, Yuto Tsukidate, Zhuoqun Li, Azusa Utsumi, Tomohiro Otsuka, Toshiaki Kato

Fullerenes-Nanotubes-Graphene General Symposium　2025/09/24
Direct fabrication of graphene/hBN-bridged superconductor junctions by plasma-enhanced chemical vapor deposition

Zhuoqun Li, Yuto Tsukidate, Hiroto Ogura, Azusa Utsumi, Tomohiro Otsuka, Toshiaki Kato

Fullerenes-Nanotubes-Graphene General Symposium　2025/09/24
Bilayer graphene quantum dot probed by RFSoC-based radio-frequency reflectometry

Motoya Shinozaki, Tomoya Johmen, Aruto Hosaka, Takumi Seo, Shunsuke Yashima, Akitomi Shirachi, Kosuke Noro, Shoichi Sato, Takashi Kumasaka, Tsuyoshi Yoshida, Tomohiro Otsuka

University of Washington - Tohoku University Quantum Materials Workshop　2025/09/25
半導体量子ハードウェアにおける機械学習アプローチ

大塚朋廣

学習物理領域研究会　2025/09/24
半導体量子ハードウェアにおける機械学習アプローチ

大塚朋廣

学習物理領域研究会　2025/09/24
オンチップ校正型高周波測定によるSrTiO3コンデンサの低温特性評価

白地昭豊鏡, 篠崎基矢, 富岡泰秀, 井上悠, 伊東謙汰, 小塚裕介, 渡邉孝信, 佐藤彰一, 熊坂武志, 大塚朋廣

日本物理学会　2025/09/18
酸化亜鉛における三重量子ドットの形成

馬場光一, 野呂康介, 小塚裕介, 熊坂武志, 篠﨑基矢, 川﨑雅司, 大塚朋廣

日本物理学会　2025/09/18
微小グラファイトバックゲートを有するMoS2量子デバイスの開発

計良雄太, 白地昭豊鏡, 篠﨑基矢, 八島俊介, 野呂康介, 熊坂武志, 内海あずさ, 谷口尚, 渡邊賢司, 大塚朋廣

日本物理学会　2025/09/18
グラフェンナノアイランド量子ドットの輸送特性評価

篠﨑基矢, 瀬尾拓未, 多田亜希子, 計良雄太, 八島俊介, 野呂康介, 熊坂武志, 内海あずさ, 松本貴士, 小林義之, 大塚朋廣

日本物理学会　2025/09/17
Machine Learning-Based Detection of Single-Electron Regime and Virtual Gate Definition in Quantum Dots

Yui Muto, Michael R. Zielewski, Motoya Shinozaki, Kosuke Noro, Tomohiro Otsuka

International Conference on Solid State Devices and Materials　2025/09/17
グラフェンジョセフソン接合集積素子に向けた接合界面制御プロセスの最適化

小倉宏斗, 李卓群, 内海あずさ, 大塚朋廣, 加藤俊顕

応用物理学会　2025/09/10
単一InAsコロイド量子ドットトランジスタにおける電気伝導特性

柴田憲治, 滝口智稀, 佐藤明, 佐々木悠人, 大塚朋廣

応用物理学会　2025/09/07
微小グラファイト電極を用いたMoS2デバイスの低温動作特性

計良雄太, 白地昭豊鏡, 篠﨑基矢, 八島俊介, 野呂康介, 熊坂武志, 内海あずさ, 谷口尚, 渡邊賢司, 大塚朋廣

ナノ・スピン実験施設研究発表会　2025/09/04
Single InAs colloidal quantum dot transistors

Kenji Shibata, Tomoki Takiguchi, Akira Sato, Yuto Sasaki, Tomohiro Otsuka

30th International Conference on Low Temperature Physics　2025/08/08
Informatics Approaches in Semiconductor Quantum Technologies Invited

Tomohiro Otsuka

The 11th Case Western Reserve X Tohoku Joint Symposium　2025/08/07
Gate-defined bilayer graphene quantum devices probed by radio-frequency reflectometry utilizing RFSoC platform

Motoya Shinozaki, Tomoya Johmen, Aruto Hosaka, Takumi Seo, Shunsuke Yashima, Akitomi Shirachi, Kosuke Noro, Shoichi Sato, Takashi Kumasaka, Tsuyoshi Yoshida, Tomohiro Otsuka

International Conference on Electronic Properties of Two-Dimensional Systems　2025/07/29
「量子コンピュータ (人工系の量子現象と半導体スピン量子ビット)」 Invited

大塚朋廣

第48回日本磁気学会サマースクール　2025/07/10
New Material Approaches for Semiconductor Quantum Technologies Invited

Tomohiro Otsuka

NIMS MANA Seminar, Tsukuba　2025/06/23
Semiconductor quantum devices based on new quantum materials Invited

Tomohiro Otsuka

University of Washington - Tohoku University Quantum Materials Workshop　2025/06/10
New materials and techniques for semiconductor quantum devices Invited

Tomohiro Otsuka

Seminar at Institute of Physics, Academia Sinica　2025/04/25
Devices utilizing new materials for semiconductor quantum technologies Invited

Tomohiro Otsuka

International VLSI Symposium on Technology, Systems and Applications　2025/04/23
Materials and Techniques for New Semiconductor Quantum Devices Invited

Tomohiro Otsuka

Seminar at Center for Quantum Science and Technology, National Tsing Hua University　2025/04/22
半導体量子情報エレクトロニクスと研究基盤技術

大塚朋廣

東北大学電気通信研究所研究基盤技術センター技術講演発表会　2025/03/31
酸化亜鉛少数電子二重量子ドットの形成

野呂康介, 篠﨑基矢, 小塚裕介, 松村和真, 藤原義弘, 熊坂武志, 塚﨑敦, 川﨑雅司, 大塚朋廣

日本物理学会　2025/03/21
機械学習による量子ドットの単一電子領域検出とバーチャルゲート定義の自動化

武藤由依, Michael R. Zielewski, 篠﨑基矢, 野呂康介, 大塚朋廣

日本物理学会　2025/03/21
Study on the response of the semiconductor quantum device to radiations

Gen Takakusa, Sei Yoshida, Yasuhiro Kishimoto, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2025/02/14
Electron transport through single nanocrystals coupled to nanogap metal leads

Kenji Shibata, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2025/02/14
Graphene nanodevice fabrication using atomic force microscopy

Keigo Tanaka, Masahiro Hara, Tomohiro Otsuka

2025/02/14
Automatic detection and analysis of charge transition lines in quantum dots by machine learning

Yui Muto, Michael R. Zielewski, Motoya Shinozaki, Kosuke Noro, Tomohiro Otsuka

The 6th International Symposium on AI and Electronics　2025/01/30
An ensemble of new materials and quantum technologies Invited

2024/12/11
New materials and techniques for semiconductor spin-based quantum technologies Invited

Tomohiro Otsuka

Impurity Spins for Quantum Information Science and Technologies　2024/12/04
Fabrication of SrTiO3-based capacitor for cryogenic variable microwave resonators”

Akitomi Shirachi, Motoya Shinozaki, Yasuhide Tomioka, Yusuke Kozuka, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2024/11/19
Analysis of Kondo state in quantum dots fabricated in ZnO heterostructures

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2024/11/19
Radio-frequency reflectometry of bilayer graphene quantum devices using RFSoC platform

Motoya Shinozaki, Tomoya Johmen, Aruto Hosaka, Takumi Seo, Shunsuke Yashima, Akitomi Shirachi, Kosuke Noro, Shoichi Sato, Takeshi Kumasaka, Takeshi Yoshida, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2024/11/19
Semiconductor quantum devices based on new materials Invited

Tomohiro Otsuka

3rd International Workshop of Spin/Quantum Materials and Devices & 6th Workshop on Quantum and Classical Cryogenic Devices, Circuits, and Systems　2024/11/06
Exploring Quantum Devices with New Materials Invited

Tomohiro Otsuka

Quantum Innovation 2024　2024/10/23
酸化亜鉛量⼦ドットの電気伝導特性と近藤効果の発現

野呂康介, 松村和真, 熊坂武志, 小塚裕介, 塚﨑敦, 川﨑雅司, 大塚朋廣

ナノ・スピン実験施設研究発表会　2024/10/02
Machine learning approaches in semiconductor quantum hardware

大塚朋廣

学習物理領域研究会、　2024/09/27
Machine learning approaches in semiconductor quantum hardware

大塚朋廣

学習物理領域研究会　2024/09/26
Quantum Dots in ZnO Heterostructures and Kondo Effects

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

The 13th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2024/09/26
Microwave resonances in disorder-induced quantum dots within GaN/AlGaN FETs

Motoya Shinozaki, Takaya Abe, Kazuma Matsumura, Takumi Aizawa, Takashi Kumasaka, Tomohiro Otsuka

The 13th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2024/09/25
RFSoCを用いた半導体量子デバイス高周波反射測定系の構築

篠﨑基矢, 上面友也, 保坂有杜, 瀬尾拓未, 八島俊介, 白地昭豊鏡, 野呂康介, 佐藤彰一, 熊坂武志, 吉田剛, 大塚朋廣

日本物理学会　2024/09/18
低温可変共振回路に向けたSrTiO3可変容量コンデンサ特性の面方位・ドープ依存性

白地昭豊鏡, 篠崎基矢, 富岡泰秀, 小塚裕介, 佐藤彰一, 熊坂武志, 大塚朋廣

日本物理学会　2024/09/18
原子間力顕微鏡による宙づりグラフェンの局所陽極酸化

田中奎伍, 柿添勇成, 松井朋裕, 大塚朋廣, 原正大

日本物理学会　2024/09/16
スピン量子ビットを用いた電子波束の単発測定手法の開発

Yunseong Jang, Han, Ngoc Tu, 藤田高史, 大塚朋廣, Arne Ludwig, Andreas D. Wieck, 山本倫久, Christopher Bäuerle, 新見康洋, 高田真太郎

日本物理学会　2024/09/16
単一PbS量子ドットトランジスタへの電気二重層ゲートの適用

滝口智稀, 高橋央輔, 大塚朋廣, 柴田憲治

応用物理学会　2024/09/16
単一ペロブスカイト量子ドットに対する電気伝導特性評価

高橋央輔, 大塚朋廣, 柴田憲治

応用物理学会　2024/09/16
New material-based approaches in quantum devices Invited

Tomohiro Otsuka

International Conference on Solid State Devices and Materials　2024/09/02
High-speed electronics for quantum devices and systems

Motoya Shinozaki, Yoshihiro Fujiwara, Tomoya Johmen, Tomohiro Otsuka

Germany-Japan mini workshop　2024/08/19
Semiconductor Quantum Devices Research at Tohoku University

Tomohiro Otsuka

Germany-Japan mini workshop,　2024/08/19
量子コンピュータ (人工系の量子現象と半導体スピン量子ビット) Invited

大塚朋廣

第47回日本磁気学会サマースクール　2024/08/08
Formation of quantum dots in ZnO heterostructures and observation of Kondo Effect

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

International Conference on the Physics of Semiconductors 2024　2024/08/01
Single PbS colloidal quantum dot transistors

Kenji Shibata, Masaki Yoshida, Kazuhiko Hirakawa, Tomohiro Otsuka, Satria Zulkarnaen Bisri, Yoshihiro Iwasa

International Conference on the Physics of Semiconductors 2024　2024/07/30
Towards Semiconductor Quantum Computers

Tomohiro Otsuka

Quantum Interaction　2024/07/30
Classifying the Charge State of Quantum Dots by Machine Learning and Improving the Performance by Visual Explanations of the Model

Yui Muto, Takumi Nakaso, Motoya Shinozaki, Takumi Aizawa, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

International Conference on the Physics of Semiconductors 2024　2024/07/30
Single PbS colloidal quantum dot transistors

Kenji Shibata, Masaki Yoshida, Kazuhiko Hirakawa, Tomohiro Otsuka, Satria Zulkarnaen Bisri, Yoshihiro Iwasa

The Materials Research Society (MRS) spring meeting　2024/04/26
単一ペロブスカイト量子ドットの電気伝導特性

高橋央輔, 大塚朋廣, 柴田憲治

2024年第71回応用物理学会春季学術講演会　2024/03/24
進行波型超伝導増幅器の集積性向上に向けた高誘電率基板上窒化ニオブ薄膜のマイクロ波特性評価

沓間弘樹, 森俊祐, 小塚裕介, 大塚朋廣, 松浦康平, 山下太郎

2024年第71回応用物理学会春季学術講演会　2024/03/22
酸化亜鉛量子ドット近藤効果の解析

野呂康介, 松村和真, 熊坂武志, 小塚裕介, 塚﨑敦, 川﨑雅司, 大塚朋廣

日本物理学会2024年春季大会　2024/03/21
GaN FETにおけるマイクロ波共鳴ピークの解析

松村和真, 阿部峰也, 篠崎基矢, 相澤拓海, 熊坂武志, 大塚朋廣

日本物理学会2024春季大会　2024/03/21
半導体量子デバイスの放射線に対する応答の研究

高草元, 岸本康宏, 吉田斉, 大塚朋廣

日本物理学会2024年春季大会　2024/03/21
Formation of quantum dots and analysis of Kondo effect in ZnO

Kosuke Noro, Yusuke Kozuka, Kazuma Matsumura, Takeshi Kumasaka, Yoshihiro Fujiwara, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

PASPS-27　2024/03/17
The study of the response of the semiconductor quantum device to radiation

Gen Takakusa, Sei Yoshida, Yasuhiro Kishimoto, Tomohiro Otsuka

UGAP2024 workshop　2024/03/05
Semiconductor Qubits and New Materials Invited

Tomohiro Otsuka

UK-Japan-Swiss Workshop ‘Materials for Quantum Electronics　2024/02/28
Improvement of Charge State Estimation in Quantum Dots by Machine Learning and Visualization of the Model by Grad-CAM

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

The 5th International Symposium on AI and Electronics　2024/02/20
Towards automatic parameter tuning of large-scale quantum system by machine learning

Takeshi Fukuhara, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2024/02/15
Single PbS colloidal quantum dot transistor

Kenji Shibata, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2024/02/15
Study on Response of Quantum Point Contact to Alpha Radiation

Sei Yoshida, Gen Takakusa, Yasuhiro Kishimoto, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2024/02/15
通信用ロジック・アルゴリズムを活用した量子古典ハイブリッド求解技術の検討

越川翔太, 保坂有杜, 西川翔太, 小西良明, 篠﨑基矢, 大塚朋廣, ハシタムトゥマラ, ウィッデヤスーリヤ, 張山昌論, 吉田剛

電子情報通信学会CS研究会　2024/01/11
Wide dynamic range charge sensing utilizing fast feedback control of radio-frequency reflectometry

Motoya Shinozaki, Yoshihiro Fujiwara, Kazuma Matsumura, Kosuke Noro, Riku Tataka, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2023/11/28
Improving the generalization performance of the machine learning model estimating charge states in quantum dots

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics,　2023/11/28
Transport Property of a Few Quantum Dots Formed in Short Channel GaN FETs

Kazuma Matsumura, Takaya Abe, Takahito Kitada, Takeshi Kumasaka, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2023/11/28
Controllable fabrication of graphene nanoribbon-based quantum dot devices

Tatsuki Kato, Mizuki Seo, Takahito Kitada, Tomohiro Otsuka, Toshiaki Kato

Symposium for the Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science and Spintronics　2023/11/28
Semiconductor nanostructures and quantum devices

Tomohiro Otsuka

AIMR Workshop　2023/11/27
High-frequency measurement in graphene nanostructures for quantum devices

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Takumi Aizawa, Tomohiro Otsuka

Workshop on Quantum and Classical Cryogenic Devices, Circuits, and Systems, Superconducting SFQ VLSI Workshop, and International Workshop of Spin/Quantum Materials and Devices,　2023/11/17
Automatic state recognition of quantum dot hardware utilizing machine learning

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

International Conference on Machine Learning Physics　2023/11/15
機械学習を用いた量子ドット電荷状態判別の汎化性能改良

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

第9回量子技術・機械学習融合ミーティング　2023/11/07
⼆層グラフェン微細構造における⾼周波反射測定⼿法の開発

上面友也, 篠崎基矢, 熊坂武志, 藤原義弘, 田高陸, 相澤拓海, 大塚朋廣

ナノ・スピン実験施設研究発表会　2023/10/05
Improving the dynamic range of charge sensing utilizing fast feedback control of rf reflectometry

Yoshihiro Fujiwara, Motoya Shinozaki, Kazuma Matsumura, Kosuke Noro, Riku Tataka, Shoichi Sato, Takeshi Kumasaka, Tomohiro Otsuka

The 12th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2023/09/28
機械学習を⽤いた量⼦ドットハードウェアの⾃動状態推定

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

学習物理領域研究会　2023/09/27
機械学習を⽤いた量⼦ドットハードウェアの⾃動状態推定

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

学習物理領域研究会　2023/09/27
Radio-frequency reflectometry in bilayer graphene quantum dot

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Takumi Aizawa, Tomohiro Otsuka

The 12th Workshop on Semiconductor/Superconductor Quantum Coherence Effect and Quantum Information　2023/09/27
単一コロイドPbS量子ドットトランジスタの電気伝導特性

柴田憲治, 吉田政希, 平川一彦, 大塚朋廣, Bisri Satria, 岩佐義宏

応用物理学会　2023/09/21
単一PbS量子ドットトランジスタの電気伝導特性

柴田憲治, 吉田政希, 平川一彦, 大塚朋廣, Bisri Satria, 岩佐義宏

日本物理学会　2023/09/17
短チャネルGaN FETにおける少数量子ドットの形成

松村和真, 阿部峰也, 北田孝仁, 熊坂武志, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会　2023/09/17
機械学習による量子ドット電荷状態推定の汎化性能改良

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

日本物理学会　2023/09/17
高周波反射測定の高速PID制御による電荷センサのダイナミックレンジ改善

篠﨑基矢, 藤原義弘, 松村和真, 野呂康介, 田髙陸, 佐藤彰一, 熊坂武志, 大塚朋廣

日本物理学会　2023/09/17
Radio-frequency reflectometry measurement in bilayer graphene microdevices

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Riku Tataka, Takumi Aizawa, Takeshi Kumasaka, Tomohiro Otsuka

International Conference on Electronic Properties of Two-Dimensional Systems　2023/06/11
Automatic charge state estimation in quantum dots by machine learning and visual explanation of the model with Grad-CAM

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

International Conference on Electronic Properties of Two-Dimensional Systems　2023/06/11
Gate-tunable carrier transport through single PbS colloidal quantum dots

Kenji Shibata, Msasaki Yoshida, Kazuhiko Hirakawa, Tomohiro, Otsuka, Satria, Z. Bisri, Yoshihiro Iwasa

International Conference on Electronic Properties of Two-Dimensional Systems　2023/06/11
Semiconductor spin qubits and new materials Invited

Tomohiro Otsuka

Workshop: Emerging Platforms for Quantum Computing　2023/04/10
量子ドット電荷状態推定機械学習モデルの予測判断根拠可視化

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

日本物理学会　2023/03/24
ナノギャップ電極と結合した単一PbS量子ドットの電気伝導特性

吉田政希, 阿部真弓, 平川一彦, 大塚朋廣, Bisri Satria, 岩佐義宏, 柴田憲治

応用物理学会　2023/03/18
Quantum dots in new materials for quantum devices Invited

Tomohiro Otsuka

International Workshop of Spin/Quantum Materials and Devices,　2023/02/24
量子ポイントコンタクトの放射線応答についての研究

吉田斉, 西川隆博, 柴田真尚, 岸本康宏, 大塚朋廣

RIEC Annual Meeting on Cooperative Research Projects　2023/02/16
Electron transport through single colloidal quantum dot coupled to nanogap metal electrodes

Kenji Shibata, Tomohiro Otsuka

RIEC Annual Meeting on Cooperative Research Projects　2023/02/16
大規模な量子系に対する自動制御技術の開発

福原武, 大塚朋廣

RIEC Annual Meeting on Cooperative Research Projects　2023/02/16
Noise Robust Automatic Recognition Method of Charge States in Quantum Dots by Machine Learning

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Motoki Shiga, Tomohiro Otsuka

The 4th International Symposium on AI and Electronics,　2023/02/13
機械学習による量子ドット状態の自動推定と制御

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 志賀元紀, 大塚朋廣

第8回量子技術・機械学習融合ミーティング　2023/01/24
Formation of quantum dots in MoS2 utilizing intrinsic Schottky barriers

Riku Tataka, Alka Sharma, Tomoya Johmen, Motoya Shinozaki, Takeshi Kumasaka, Yong P. Chen, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science　2022/10/25
High-frequency measurement in bilayer graphene nanodevices

Tomoya Johmen, Motoya Shinozaki, Yoshihiro Fujiwara, Riku Tataka, Takumi Aizawa, Takeshi Kumasaka, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science,　2022/10/25
Kondo Effects in ZnO Quantum Dots

Kosuke Noro, Takeshi Kumasaka, Yoshihiro Fujiwara, Yusuke Kozuka, Atsushi Tsukazaki, Masashi Kawasaki, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science,　2022/10/25
Charge state recognition in double quantum dot devices by machine learning

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science　2022/10/25
二層グラフェン微小デバイスにおける高周波反射測定

上面友也, 篠崎基矢, 熊坂武志, 藤原義弘, 田高陸, 相澤拓海, 大塚朋廣

日本物理学会　2022/09/13
MoS2におけるコンタクト，ゲート電極の開発と量子ドット形成

田髙陸, Alka Sharma, 上面友也, 篠崎基矢, 熊坂武志, Yong P. Che, 大塚朋廣

日本物理学会　2022/09/13
酸化亜鉛量子ドットの形成と近藤効果の観測

野呂康介, 熊坂武志, 藤原義弘, 小塚裕介, 塚﨑敦, 川﨑雅司, 大塚朋廣

日本物理学会　2022/09/13
Noise robust recognition of charge states in quantum dots by machine learning and preprocessing

Yui Muto, Takumi Nakaso, Takumi Aizawa, Motoya Shinozaki, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Atsunori Kanemura, Tomohiro Otsuka

International Conference on the Physics of Semiconductors 2022　2022/06/28
ナノギャップ電極と結合したPbS量子ドットにおける電気伝導特性

柴田憲治, 齋藤光貴, 大塚朋廣

応用物理学会　2022/03/23
半導体量子ビット研究の最前線シンポジウムはじめに

大塚朋廣

日本物理学会　2022/03/18
高周波反射測定による量子ドットQCA状態電荷遷移の実時間観測

相澤拓海, 篠﨑基矢, 藤原義弘, 熊坂武, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 大塚朋廣

日本物理学会　2022/03/16
GaN FETの電流コラプス下における量子ドット形成

阿部峰也, 篠崎基矢, 相澤拓海, 熊坂武志, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会　2022/03/16
機械学習と前処理によるノイズ耐性のある量子ドット電荷状態推定

武藤由依, 中曽拓, 相澤拓海, 篠﨑基矢, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 大塚朋廣

日本物理学会　2022/03/16
量子ポイントコンタクトの放射線応答

湯田秀明, 吉田斉, 大塚朋廣, 岸本康宏

日本物理学会　2022/03/16
微細CoFeB/MgO磁気トンネル接合における非線形電子輸送特性

篠﨑基矢, 五十嵐純太, 岩切秀一, 北田孝仁, 早川佳祐, 陣内佛霖, 大塚朋廣, 深見俊輔

日本物理学会　2022/03/15
Noise analysis of radio-frequency reflectometry for single spin and charge detection in quantum dots Invited

Tomohiro Otsuka, Motoya Shinozaki, Yui Muto, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Takumi Ito, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

1st Online RIEC International Workshop on Spintronics　2021/11/18
Quantum dots formed in GaN/AlGaN FETs and channel length dependence

Takaya Abe, Takahito Kitada, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

International Conference on Electronic Properties of Two-Dimensional Systems　2021/11/02
Channel length dependence of the formation of quantum dots in GaN FETs

Takaya Abe, Takahito Kitada, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science　2021/10/27
Error rate analysis of charge sensing in quantum dots by Bayesian approach

Motoya Shinozaki, Yui Muto, Takahito Kitada, Shuya Nagayasu, Takeshi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Sen Li, Takumi Ito, Seigo Tarucha, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science　2021/10/27
Improving low temperature contact resistance of 2D semiconductors using semimetal

Alka Sharma, Tomohiro Otsuka, Yong P. Chen

Symposium for The Core Research Clusters for Materials Science and Spintronics, and International Joint Graduate Program in Materials Science　2021/10/25
GaN FETにおけるマイクロ波依存伝導の観測

阿部峰也, 篠崎基矢, 相澤拓海, 熊坂武志, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会　2021/09/21
電荷検出器への応用に向けた金属ナノ接合の微細化と伝導特性制御

柴田憲治, 佐々木尚人, 斉藤大我, 大塚朋廣, 平川一彦

応用物理学会　2021/03/16
CVDグラフェンナノリボンにおける単一量子ドット形成

北田孝仁, 阿部峰也, 瀬尾瑞樹, 佐藤尚郁, 篠﨑基矢, 相澤拓海, 武藤由依, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会　2021/03/15
GaN FET中量子ドット形成のチャネル長依存性

阿部峰也, 北田孝仁, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会　2021/03/13
半導体量子ドットを用いた電子スピン状態の測定と制御 Invited

大塚朋廣

日本物理学会　2021/03/12
Readout noise in radio-frequency reflectometry in gallium arsenide quantum dots

Motoya Shinozaki, Yui Muto, Takahito Kitada, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Takumi Ito, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha, Tomohiro Otsuka

International Symposium for The Core Research Clusters for Materials Science and Spintronics　2021/02/24
Charge state estimation in quantum dots by Bayesian approach

Yui Muto, Motoya Shinozaki, Takahito Kitada, Shuya Nagayasu, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Sen Li, Takumi Ito, Seigo Tarucha, Tomohiro Otsuka

International Symposium for The Core Research Clusters for Materials Science and Spintronics　2021/02/24
Quantum Dots in plasma CVD Graphene Nanoribbons

Takahito Kitada, Mizuki Seo, Takaya Abe, Motoya Shinozaki, Naohumi Sato, Takumi Aizawa, Yui Muto, Toshiro Kaneko, Toshiaki Kato, Tomohiro Otsuka

International Symposium for The Core Research Clusters for Materials Science and Spintronics　2021/02/24
CVDグラフェンナノリボンにおける量子ドット形成

北田孝仁, 阿部峰也, 篠﨑基矢, 瀬尾瑞樹, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会　2020/09/11
機械学習による量子ドットの電荷状態推定

中曽拓, 篠﨑基矢, 相澤拓海, 北田孝仁, 武藤由依, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健, 野入亮人, 伊藤匠, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 兼村厚範, 大塚朋廣

日本物理学会　2020/09/09
量子ドット高周波反射測定のノイズ解析

篠﨑基矢, 武藤由依, 北田孝仁, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, 伊藤匠, Arne Ludwig, Andreas D. Wieck, 樽茶清悟, 大塚朋廣

日本物理学会　2020/09/09
ベイズ手法による量子ドット電荷状態推定のノイズ依存性

武藤由依, 篠﨑基矢, 北田孝仁, 永安修也, 中島峻, Matthieu R. Delbecq, 米田淳, 武田健太, 野入亮人, Sen Li, 伊藤匠, 樽茶清悟, 大塚朋廣

日本物理学会　2020/09/09
半導体微細構造を用いた量子デバイス Invited

大塚朋廣

東京大学物性研究所ワークショップ「ナノスケール物性科学の最先端と新展開」　2020/07/22
CVDグラフェンナノリボンの電気伝導特性測定

北田孝仁, 阿部峰也, 瀬尾瑞樹, 金子俊郎, 加藤俊顕, 大塚朋廣

日本物理学会　2020/04/01
GaN FET中量子ドット形成の絶縁膜依存性

阿部峰也, 北田孝仁, 伊藤範和, 田中岳利, 中原健, 大塚朋廣

日本物理学会　2020/04/01
Measurement and Control of Single-electron Spins by Utilizing Semiconductor Quantum Dot Invited

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

Symposium for The Core Research Clusters for Materials Science and Spintronics　2020/02/10
Quantum dots formed in GaN FETs

Takaya Abe, Takahito Kitada, Norikazu Ito, Taketoshi Tanaka, Ken Nakahara, Tomohiro Otsuka

Symposium for The Core Research Clusters for Materials Science and Spintronics　2020/02/10
Spin and Charge Dynamics in Nanostructures Probed by Quantum Dot Sensors

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

New Perspective in Spin Conversion Science　2020/02/03
Spin Dynamics in Nanostructures Probed by Quantum Dot Sensors

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

Materials Research Meeting 2019　2019/12/11
Speed up of quantum dot sensors utilizing Bayesian estimation

Tomohiro Otsuka, Shuya Nagayasu, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Sen Li, Takumi Ito, Seigo Tarucha

International Symposium on Materials Informatics　2019/02/10
Probing Spin Dynamics in Nanostructures Utilizing Quantum Dot Sensors

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

2018/11/22
Charge and Spin Dynamics in a Quantum Dot-Lead Hybrid System Invited

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Sen Li, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

International Symposium on Frontiers of Quantum Transport in Nano Science　2018/11/09
Speed up of quantum dot charge sensing utilizing Bayesian estimation International-presentation

Tomohiro Otsuka, Shuya Nagayasu, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Sen Li, Takumi Ito, Seigo Tarucha

International Conference on the Physics of Semiconductors　2018/07/30
Different charge and spin dynamics in a quantum dot-lead coupled system International-presentation

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2018/01/15
Probing Dynamics of Local Electronic States in Nanostructures Utilizing Fast Quantum Dot Probes International-presentation

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Peter Stano, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

International Symposium on Fluctuation and Structure out of Equilibrium　2017/11/21
Four Single-spin Rabi Oscillations in a Quadruple Quantum Dot International-presentation

Takumi Ito, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Akito Noiri, Giles Allison, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

International Conference on Electronic Properties of Two Dimensional Systems　2017/08/03
Difference in Charge and Spin Dynamics in a Quantum Dot-Lead Hybrid System International-presentation

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Peter Stano, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

International Conference on Electronic Properties of Two Dimensional Systems　2017/08/01
Fast Local Electronic Probes utilizing Quantum Dots for Fluctuation Measurement in Nanodevices

Tomohiro Otsuka, Shinichi Amaha, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Retsu Sugawara, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

新学術領域「ゆらぎと構造」第3回領域研究会　2016/06/17
AC Stark effect and optimal control of a strongly driven Si/SiGe quantum dot spin qubit International-presentation

K. Takeda, J. Kamioka, J. Yoneda, T. Otsuka, M. R. Delbecq, G. Allison, T. Nakajima, T. Kodera, S. Oda, S. Tarucha

Silicon Quantum Electronics Workshop　2016/06
Multiplexed reflectometry measurement of a gate-defined Si-MOS quantum dot International-presentation

J. Yoneda, T. Honda, K. Takeda, M. Marx, T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, G. Allison, T. Kodera, S. Oda, S. Tarucha

Silicon Quantum Electronics Workshop　2016/06
Measurement of charge states in Si/SiGe multiple quantum dots International-presentation

T. Otsuka, K. Takeda, J. Yoneda, T. Honda, M. R. Delbecq, G. Allison, M. Marx, T. Nakajima, T. Kodera, S. Oda, Y. Hoshi, N. Usami, K. M. Itoh, S. Tarucha

Silicon Quantum Electronics Workshop　2016/06
Measurement of spin relaxation in semiconductor quantum dots coupled to electric leads

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Akito Noiri, Takumi Ito, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

ImPACT量子情報技術ワークショップ　2016/03/29
Hybrid cQED architecture as a model system for non-equilibrium physics in condensed matter

Matthieu R. Delbecq, Giles Allison, Takashi Nakajima, Jun Yoneda, Kenta Takeda, Marian Marx, Tomohiro Otsuka, Shinich Amaha, Seigo Tarucha

ImPACT量子情報技術ワークショップ　2016/03/29
三重量子ドットにおける準安定電荷状態を利用したスピン・電荷変換

中島峻, Matthieu R. Delbecq, 大塚朋廣, 天羽真一, 米田淳, 野入亮人, 武田健太, Giles Allison、Arne Ludwig, Andreas D. Wieck, 樽茶清悟

日本物理学会　2016/03/19
三重量子ドット電子スピン共鳴における局所磁場差と交換相互作用の競合

米田淳, 野入亮人, 中島峻, 大塚朋廣, M. Delbecq, 天羽真一, Arne Ludwig, Andreas D. Wieck, 樽茶清悟

日本物理学会　2016/03/19
電極と結合した量子ドットにおけるスピン緩和測定

大塚朋廣, 中島峻, Matthieu R. Delbecq, 天羽真一, 米田淳, 武田健太, Giles Allison, 野入亮人, 伊藤匠, Arne Ludwig, Andreas D. Wieck, 樽茶清悟

日本物理学会　2016/03/19
Measurement of charge states in multiple quantum dots utilizing multiplexed fast charge sensors

Takumi Ito, Tomohiro Otsuka, Shinichi Amaha, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Akito Noiri, Takashi Nakajima, Seigo Tarucha

東京大学低温センター研究交流会　2016/02/23
Coherent electron-spin-resonance control of three individual spins in a triple quantum dot International-presentation

A. Noiri, J. Yoneda, T. Nakajima, T. Otsuka, M. R. Delbecq, K. Takeda, S. Amaha, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/14
Hybrid cQED architecture as a model system for non-equilibrium physics in condensed matter International-presentation

G. Allison, M. R. Delbecq, N. Lambert, T. Nakajima, J. Yoneda, K. Takeda, M. Marx, T. Otsuka, S. Amaha, F. Nori, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/13
Bayesian estimation of nuclear-spin bath for adaptive feedback with a single-electron spin qubit International-presentation

K. Kawasaki, T. Nakajima, J. Yoneda, M. R. Delbecq, S. Amaha, T. Otsuka, K. Takeda, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/13
Controlling entanglement of spin qubits in a triple quantum dot International-presentation

T. Nakajima, M. R. Delbecq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, K. Takeda, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/13
Electron spin resonance in a quadruple quantum dot International-presentation

T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, J. Yoneda, K. Takeda, A. Noiri, R. Sugawara, A. Ludwig, A. D. Wieck, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/13
A fast addressable spin qubit in a silicon quantum dot International-presentation

K. Takeda, J. Kamioka, T. Otsuka, J. Yoneda, T. Nakajima, M. R. Delbecq, S. Amaha, G. Allison, A. Noiri, R. Sugawara, T. Kodera, S. Oda, S. Tarucha

International Symposium on Dynamics in Artificial Quantum Systems　2016/01/13
Exploiting the slow dynamics of nuclear spins to enhance the coherence time of spin qubits in GaAs International-presentation

M. R. Delbecq, T. Nakajima, P. Stano, T. Otsuka, S. Amaha, J. Yoneda, K. Takeda, G. Allison, A. Ludwig, A. D. Wieck, S. Tarucha

International Symposium on Nanoscale Transport and Technology　2015/11/20
Generation of locally and non-locally entangled electron spin pairs in a triple quantum dot International-presentation Invited

T. Nakajima, M. R. Delbecq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, K. Takeda, A. Ludwig, A. D. Wieck, S. Tarucha

International Workshop : Quantum Nanostructures and Electron-Nuclear Spin Interactions　2015/10/20
半導体量子ドットを用いたスピンキュービット実験 Invited

大塚朋廣, 中島峻, M. Delbecq, 天羽真一, 米田淳, 武田健太, 野入亮人, 菅原烈, 伊藤匠, 川崎賢人, H. Lu, B, Shojaei、C. Palmstrom、A. Gossard, J. Watson, M. Manfra、A. Ludwig, A. Wieck, 樽茶清悟

第4回関西若手物性研究会　2015/10/17
三角形型三重量子ドットの電荷輸送特性

川崎賢人, 野入亮人, 天羽真一, 大塚朋廣, 中島峻, 米田淳, M. Delbecq, 武田健太, 樽茶清悟

日本物理学会　2015/09/17
四重量子ドットにおける単一電子スピン共鳴

大塚朋廣, 中島峻, Matthieu Delbecq, 天羽真一, 米田淳, 武田健太, 野入亮人, 菅原烈, Giles Allison、Arne Ludwig, Andreas Wieck, 樽茶清悟

日本物理学会　2015/09/16
高速複数電荷計を用いた多重量子ドット電荷状態の観測

伊藤匠, 大塚朋廣, 天羽真一, 中島峻, Matthieu Delbecq, 米田淳, 武田健太, Giles Allison, 野入亮人, 樽茶清悟

日本物理学会　2015/09/16
電極閉じ込め型シリコンMOS量子ドットの作製と評価

米田淳, 本田拓夢, 武田健太, Marian Marx, 大塚朋廣, 中島峻, Matthieu Delbecq, 天羽真一, Giles Allison, 小寺哲夫, 小田俊理, 樽茶清悟

日本物理学会　2015/09/16
Si2重量子ドット中の電子スピンの高速独立操作

武田健太, 神岡純, 小幡利顕, 大塚朋廣, 中島峻, Matthieu Delbecq, 天羽真一, 米田淳, Giles Alison, 野入亮人, 菅原烈, 小寺哲夫, 小田俊理, 樽茶清悟

日本物理学会　2015/09/16
三重量子ドットにおける非隣接スピンもつれ状態の形成と観測

中島峻, Matthieu R. Delbecq, 大塚朋廣, 天羽真一, 米田淳, 野入亮人, 武田健太, Arne Ludwig, Andreas D. Wieck, 樽茶清悟

日本物理学会　2015/09/16
Coherence of spin qubits measured faster than the decorrelation time of their environmental noise

Matthieu R. Delbecq, Takashi Nakajima, Tomohiro Otsuka, Shinichi Amaha, Jun Yoneda, Akito Noiri, Arne Ludwig, Andreas D. Wieck, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
A fast addressable single-spin qubit in a Si/SiGe double quantum dot with a micromagnet

Kenta Takeda, Jun Kamioka, Toshiaki Obata, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Jun Yoneda, Giles Allison, Akito Noiri, Retsu Sugawara, Tetsuo Kodera, Syunri Oda, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
A tunnel-coupled triangular triple quantum dot

Akito Noiri, Kento Kawasaki, Shinichi Amaha, Tomohiro Otsuka, Takashi Nakajima, Jun Yoneda, Matthieu R. Delbecq, Kenta Takeda, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
cQED incorporating SiGe quantum dots

Giles Allison, Matthieu R. Delbecq, Takashi Nakajima, Jun Yoneda, Kenta Takeda, Marian Marx, Tomohiro Otsuka, Shinich Amaha, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
Electrical characterization of silicon metel-oxide-semiconductor-based quantum dots

Jun Yoneda, Takumu Honda, Kenta Takeda, Marian Marx, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinichi Amaha, Giles Allison, Tetsuo Kodera, Syunri Oda, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
Enhancement of coherent time of a spin qubit by fast feedback in nuclear spin bath fluctuation

Kento Kawasaki, Takashi Nakajima, Jun Yoneda, Matthieu R. Delbecq, Shinichi Amaha, Tomohiro Otsuka, Kenta Takeda, Seigo Tarutya

半導体量子効果と量子情報の夏期研修会　2015/09/11
Increasing valley-splitting in Si/SiGe quantum dots

Marian Marx, Jun Yoneda, Giles Allison, Matthieu R. Delbecq, Takumu Honda, Tomohiro Otsuka, Kenta Takeda, Shinichi Amaha, Takashi Nakajima, Retsu Sugawara, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2015/09/11
Probing spin states in a triple quantum dot by Fourier transform spectroscopy International-presentation

T. Nakajima, M. R. Delbecq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, K. Takeda, A. Ludwig, A. D. Wieck, S. Tarucha

SpinTech VIII　2015/08/12
A strongly driven single-spin qubit in a Si/SiGe double quantum dot with a micro-magnet International-presentation

K. Takeda, J. Kamioka, T. Obata, T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, J. Yoneda, A. Noiri, R. Sugawara, T. Kodera, S. Oda, S. Tarucha

SpinTech VIII　2015/08/12
Implementation of three spin qubits in a lateral triple quantum dot International-presentation

A. Noiri, T. Nakajima, J. Yoneda, M. R. Delbecq, T. Otsuka, S. Amaha, K. Takeda, A. Ludwig, A. D. Wieck, S. Tarucha

SpinTech VIII　2015/08/11
A fast addressable single-spin qubit in a Si/SiGe double quantum dot with a micro-magnet International-presentation

K. Takeda, J. Kamioka, T. Obata, T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, J. Yoneda, G. Allison, A. Noiri, R. Sugawara, T. Kodera, S. Oda, S. Tarucha

Silicon Quantum Electronics Workshop 2015　2015/08/04
Improved design and fabrication for Si/SiGe quantum dots with increased valley-splitting International-presentation

M. Marx, K. Takeda, J. Yoneda, G. Allison, T. Honda, M. R. Delbecq, T. Otsuka, T. Nakajima, S. Amaha, T. Kodera, S. Oda, S. Tarucha

Silicon Quantum Electronics Workshop 2015　2015/08/03
Fabrication and characterization of gate-defined small Si-MOS quantum dot devices International-presentation

J. Yoneda, T. Honda, K. Takeda, M. Marx, T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, G. Allison, T. Kodera, S. Oda, S. Tarucha

Silicon Quantum Electronics Workshop 2015　2015/08/03
Enhanced coherence time of spin qubits in GaAs and dynamics of the nuclear spin bath International-presentation

M. R. Delbecq, T. Nakajima, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, A. Ludwig, A. D. Wieck, S. Tarucha

International Conference on Electronic Properties of Two-Dimensional Systems　2015/07/28
Realization of a Fast Single-lead Quantum Dot Probe and Evaluation of the Properties by Probing Quantum Dot States International-presentation

T. Otsuka, S. Amaha, T. Nakajima, M. R. Delbecq, J. Yoneda, K. Takeda, R. Sugawara, A. Ludwig, A. D. Wieck, S. Tarucha

International Conference on Electronic Properties of Two-Dimensional Systems　2015/07/28
Electrically Pulsed Fourier Transform Spectroscopy of Coupled Electron Spins in Triple Quantum Dot International-presentation

T. Nakajima, M. R. Delbecq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, K. Takeda, A. Ludwig, A. D. Wieck, S. Tarucha

International Conference on Electronic Properties of Two-Dimensional Systems　2015/07/28
Boosting single electron spin flips in quantum dots International-presentation

T. Ito, J. Yoneda, K. Takeda, A. Noiri, T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, S. Tarucha

International Conference on Modulated Semiconductor Structures　2015/07/27
A tunnel-coupled triangular triple quantum dot International-presentation

A. Noiri, K. Kawasaki, S. Amaha, T. Otsuka, T. Nakajima, J. Yoneda, M. R. Delbecq, K. Takeda, S. Tarucha

International Conference on Electronic Properties of Two-Dimensional Systems　2015/07/27
Single-electron Spin Resonance in a Quadruple Quantum Dot International-presentation

T. Otsuka, T. Nakajima, M. R. Delbecq, S. Amaha, J. Yoneda, K. Takeda, A. Noiri, R. Sugawara, A. Ludwig, A. D. Wieck, S. Tarucha

International Conference on Electronic Properties of Two-Dimensional Systems　2015/07/27
Exploring multiple quantum dots circuits charge stability diagrams

Matthieu Delbecq, Takashi Nakajima, Tomohiro Otsuka, Shinichi Amaha, Jun Yoneda, John Watson, Michael Manfra, Seigo Tarucha

日本物理学会　2015/03/23
シングルリード量子ドットプローブの高速化と量子ドット状態測定による性能評価

大塚朋廣, 天羽真一, 中島峻, DELBECQ M, 米田淳, 武田健太, 菅原烈, LUDWIG Arne, WIECK Andreas, 樽茶清悟

日本物理学会　2015/03/23
3重量子ドットを用いた3スピン量子ビットの共鳴周波数・ラビ振動数の特性

野入亮人, 米田淳, 中島峻, 大塚朋廣, Matthieu Delbecq, 天羽真一, Arne Ludwig, Andreas Wieck, 樽茶清悟

日本物理学会　2015/03/23
電子スピン共鳴によるSi量子ドット中のスピン・バレー状態の考察

武田健太, 神岡純, 小幡利顕, 大塚朋廣, 中島峻, DELBECQ M.R, 天羽真一, 米田淳, 野入亮人, 菅原烈, 小寺哲夫, 小寺哲夫, 小寺哲夫, 小田俊理, 樽茶清悟

日本物理学会　2015/03/23
三重量子ドットにおけるスピン量子ビット実験の忠実度向上

中島峻, DELBECQ M.R, 大塚朋廣, 天羽真一, 米田淳, 野入亮人, 武田健太, LUDWIG Arne, WIECK Andreas D, 樽茶清悟

日本物理学会　2015/03/23
アルミナ絶縁層を用いた傾斜磁場ESR法の改善

伊藤匠, 野入亮人, 米田淳, 米田淳, 中島峻, 中島峻, 大塚朋廣, 大塚朋廣, 天羽真一, 樽茶清悟, 樽茶清悟

日本物理学会　2015/03/23
Boosting single electron spin flips in quantum dots by device engineering

伊藤匠, 野入亮人, 米田淳, 中島峻, 大塚朋廣, 天羽真一, 樽茶清悟

MERIT自主キャンプ　2015/03/10
Implementation of three spin qubits in a lateral triple quantum dot International-presentation

A. Noiri, T. Nakajima, J. Yoneda, M. Delbecq, T. Otsuka, S. Amaha, A. Ludwig, A. D. Wieck, S. Tarucha

International Workshop on Topological Electronics　2015/03/09
Single-electron spin resonance in a Si/SiGe double quantum dot with a micromagnet International-presentation

K. Takeda, J. Kamioka, T. Obata, T. Otsuka, T. Nakajima, M. Delbecq, S. Amaha, J. Yoneda, A. Noiri, R. Sugawara, T. Kodera, S. Oda, S. Tarucha

American Physical Society March Meeting　2015/03/05
Addressable single-spin control in multiple quantum dots coupled in series International-presentation Invited

T. Nakajima, M. R. Delbeq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, A. D. Wieck, S. Tarucha

American Physical Society March Meeting　2015/03/04
Vanishing Influence from Nuclear Spins on Strongly Driven Single Electron Spins in Quantum Dots International-presentation

J. Yoneda, T. Otsuka, T. Nakajima, T. Takakura, T. Obata, M.l Pioro-Ladriere, H. Lu, C. Palmstrom, A. C. Gossard, S. Tarucha, ual, contri

International Symposium on Quantum System and Nuclear Spin Related Phenomena　2015/02/19
Increase by several orders of magnitude of the spin coherence time in GaAs by fast measurements International-presentation

M. R. Delbecq, T. Nakajima, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, A. Ludwig, A. D. Wieck, S. Tarucha

International Symposium on Quantum System and Nuclear Spin Related Phenomena　2015/02/19
超高速量子ドットプローブを用いた半導体微細構造中の局所電子状態のダイナミクスの研究

大塚朋廣, 天羽真一, 中島峻, Matthieu Delbecq, 米田淳, 武田健太, 菅原烈, Arne Ludwig, Andreas Wieck, 樽茶清悟

理研奨励ファンド成果報告会　2015/01/14
Addressable Control of Three Spin Qubits in Semiconductor Triple Quantum Dot International-presentation

M. R. Delbeq, T. Nakajima, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, A. D. Wieck, S. Tarucha

Workshop on Innovative Nanoscale Devices and Systems　2014/12/01
Experimental Study of Spin Qubits in Triple Quantum Dot

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinich Amaha, Jun Yoneda, Kenta Takeda, Akito Noiri, Retsu Sugawara, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2014/09/13
Fabrication of silicon quantum devices with the goal of the implementation of a Triple Quantum Dot

Marian Marx, Jun Yoneda, Giles Allison, Matthieu R. Delbecq, Takumu Honda, Tomohiro Otsuka, Kenta Takeda, Shinichi Amaha, Takashi Nakajima, Retsu Sugawara, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2014/09/12
Implementation of three spin qubits in a lateral triple quantum dot

Akito Noiri, Jun Yoneda, Takashi Nakajima, Tomohiro Otsuka, Shinichi Amaha, Matthieu R. Delbecq, Andreas D. Wieck, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2014/09/12
Vertically and Laterally Coupled Quadruple Quantum Dot

Shinich Amaha, Matthieu R. Delbecq, Takashi Nakajima, Tomohiro Otsuka, Jun Yoneda, Keiji Ono, Tsuyoshi Hatano, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2014/09/12
Full Control of a Quadruple Quantum Dot Circuit Charge States in the Single Electron Regime

Matthieu R. Delbecq, Takashi Nakajima, Tomohiro Otsuka, Shinichi Amaha, John D. Watson, Michael J. Manfra, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2014/09/11
微小磁石を備えたSi/SiGe2重量子ドットにおける単一電子スピン共鳴

武田健太, 神岡純, 小幡利顕, 大塚朋廣, 中島峻, DELBECQ M, 天羽真一, 米田淳, 野入亮人, 菅原烈, 小寺哲夫, 小田俊理, 樽茶清悟

日本物理学会　2014/09/08
三重量子ドットを用いたスピン・キュービット実験 II

中島峻, 大塚朋廣, DELBECQ Matthieu, 天羽真一, 米田淳, 野入亮人, 武田健太, 菅原烈, 樽茶清悟

日本物理学会　2014/09/08
三重量子ドットを用いたスピン・キュービット実験 I

大塚朋廣, 中島峻, DELBECQ M, 天羽真一, 米田淳, 野入亮人, 武田健太, 菅原烈, 樽茶清悟

日本物理学会　2014/09/08
Full control of quadruple quantum dot circuit charge states in the single electron regime International-presentation

M. R. Delbecq, T. Nakajima, T. Otsuka, S. Amaha, J. D. Watson, M. J. Manfra, S. Tarucha

International Conference on The Physics of Semiconductors　2014/08/13
Addressable control of single spin qubits in lateral triple quantum dot International-presentation

T. Nakajima, M. R. Delbeq, T. Otsuka, S. Amaha, J. Yoneda, A. Noiri, A. D. Wieck, S. Tarucha

International Conference on Low Temperature Physics　2014/08/08
縦横結合4重量子ドットの電気伝導特性

天羽真一, M. Delbecq, 中島峻, 大塚朋廣, 大野圭司, D. G. Austing, 羽田野剛司, 樽茶清悟

日本物理学会　2014/03/29
Fast Single Spin Operation in Semiconductor Quantum Dots International-presentation

T. Otsuka, J. Yoneda, T. Nakajima, T. Takakura, K. Yoshida, T. Obata, S. Tarucha, ual, contri

FIRST International Symposium on Topological Quantum Technology　2014/01/29
Scaling-up Spin Qubits in Semiconductor Quantum Dots International-presentation

T. Nakajima, T. Otsuka, M. R. Delbeq, S. Amaha, J. Yoneda, A. Noiri, K. Takeda, J. Kamioka, R. Sugawara, J. Watson, M. J. Manfra, A. D. Wieck, S. Tarucha

FIRST International Symposium on Topological Quantum Technology　2014/01/29
Fast Single Spin Operation in Semiconductor Quantum Dots

Tomohiro Otsuka, Jun Yoneda, Takashi Nakajima, Tatsuki Takakura, Katsuharu Yoshida, Toshiaki Obata, Seigo Tarucha

Emergent Matter Science Research Facility Work Shop　2013/12/20
Fast Single Spin Operation in Semiconductor Quantum Dots

Tomohiro Otsuka, Jun Yoneda, Takashi Nakajima, Tatsuki Takakura, Katsuharu Yoshida, Toshiaki Obata, Seigo Tarucha, ual contributi

量子サイバネティクス全体会議　2013/12/16
Single-step Z Rotation of a Single Spin Qubit in a Semiconductor Quantum Dot

Jun Yoneda, Tomohiro Otsuka, Takashi Nakajima, Tatsuki Takakura, Katsuharu Yoshida, Toshiaki Obata, S. Tarucha, ual, contri

量子情報処理プロジェクト全体会議　2013/12
Scale-up of spin qubits in semiconductor quantum dots

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbeq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Akito Noiri, Jun Kamioka, Retsu Sugawara, John Watson, Michael J. Manfra, Hong Lu, Borzoyeh Shojaei, Christopher Palmstrøm, Arthur Gossard, S. Tarucha

量子情報処理プロジェクト全体会議　2013/12
単一電子スピン量子ビットの位相ゲート

米田淳, 大塚朋廣, 中島峻, 高倉樹, 小幡利顕, 樽茶清悟

日本物理学会　2013/09/27
3端子3重量子ドットにおけるパウリスピンブロッケード

野入亮人, 高倉樹, 小幡利顕, 大塚朋廣, 中島峻, 米田淳, 樽茶清悟

日本物理学会　2013/09/27
量子ポイントコンタクトを用いた量子ホールエッジ状態におけるエネルギー緩和の観測

大塚朋廣, 大月朋廣, 杉原裕規, 米田淳, 中島峻, 樽茶清悟

日本物理学会　2013/09/26
Recent Progress on GaAs-based Spin Qubits

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Shinich Amaha, Jun Yoneda, Kenta Takeda, Akito Noiri, Jun Kamioka, Katsuharu Yoshida, Toshiaki Obata, Hong Lu, Borzoyeh Shojaei, Christopher Palmstrøm, Arthur Gossard, John Watson, Michael J. Manfra, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2013/09/04
Spin-based Quantum Information Processing with Quantum Dots

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Seigo Tarucha

RIKEN 異分野交流の夕べ　2013/08
Direct phase control of a single spin qubit International-presentation

J. Yoneda, T. Otsuka, T. Nakajima, T. Takakura, T. Obata, H. Lu, C. Palmstrom, A. C. Gossard, S. Tarucha, ual, contri

International School and Conference on Spintronics and Quantum Information Technology　2013/07/31
Coherent dynamics of a strongly driven single electron spin International-presentation

J. Yoneda, T. Otsuka, T. Nakajima, T. Takakura, T. Obata, H. Lu, C. Palmstrom, A. C. Gossard, S. Tarucha, ual, contri

International Conference on Electronic Properties of Two-dimentional Systems　2013/07/04
Probing energy relaxation in quantum Hall edge states utilizing quantum point contacts International-presentation

T. Otsuka, Y. Sugihara, J. Yoneda, T. Nakajima, S. Tarucha, ual, contri

International Conference on Electronic Properties of Two-dimentional Systems　2013/07/02
Spin-based Quantum Information Processing with Quantum Dots

Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Jun Yoneda, Kenta Takeda, Seigo Tarucha

RIKEN CEMS One Day Workshop　2013/04
トンネル結合制御可能な横型4重量子ドット

野入亮人, 高倉樹, 小幡利顕, 大塚朋廣, 米田淳, 吉田勝治, 樽茶清悟

日本物理学会　2013/03/29
単一電子スピン高速ラビ振動の時間分解測定

米田淳, 大塚朋廣, 中島峻, 高倉樹, 小幡利顕, 樽茶清悟

日本物理学会　2013/03/29
GaAs系量子ポイントコンタクトにおけるコンダクタンスの揺らぎのゲートバイアス依存性

中島峻, 大塚朋廣, 米田淳, 野入亮人, 樽茶清悟

日本物理学会　2013/03/26
Fast electrical manipulation of single electron spins in semiconductor quantum dots

Jun Yoneda, Tomohiro Otsuka, Takashi Nakajima, Tatsuki Takakura, Katsuharu Yoshida, Toshiaki Obata, Seigo Tarucha, Hong Lu, Borzoyeh Shojaei, Christopher Palmstrøm, Arthur Gossard

量子情報処理プロジェクト、量子サイバネティクス全体会議　2012/12
Detection of spin polarization utilizing singlet and triplet states in a single-lead quantum dot

Tomohiro Otsuka, Yuuki Sugihara, Jun Yoneda, Shingo Katsumoto, Seigo Tarucha

半導体量子効果と量子情報の夏期研修会　2012/09/06
Recent progress in a semiconductor quantum dot system for quantum computation - speeding up and scaling up

Jun Yoneda, Tomohiro Otsuka, Takashi Nakajima, Akito Noiri, Tatsuki Takakura, Kenta Takeda, Toshiaki Obata, Katsuharu Yoshida, Seigo Tarucha, Hong Lu, Borzoyeh Shojaei, Christopher Palmstrøm, Arthur Gossard

半導体量子効果と量子情報の夏期研修会　2012/09/06
Fast Electrical Control of Single Spins in Semiconductor Quantum Dots International-presentation

J. Yoneda, T. Otsuka, T. Takakura, K. Yoshida, T. Obata, S. Tarucha, H. Lu, C. Palmstrom, A. C. Gossard, qual contribution

International Conference on the Physics of Semiconductors　2012/08/02
Single to Quadruple Quantum Dots with Tunable Interdot Tunnel Couplings International-presentation

T. Takakura, A. Noiri, T. Obata, T. Otsuka, J. Yoneda, K. Yoshida, S. Tarucha

International Conference on the Physics of Semiconductors　2012/08/02
Detection of spin polarization with two-electron states in a single-lead quantum dot International-presentation

T. Otsuka, Y. Sugihara, J. Yoneda, S. Katsumoto, S. Tarucha

International Conference on the Physics of Semiconductors　2012/07/30
Speed-up of spin manipulations in semiconductor quantum dots International-presentation

T. Otsuka, J. Yoneda, T. Takakura, K. Yoshida, T. Obata, S. Tarucha, H. Lu, C. Palmstrom, A. C. Gossard, qual contribution

International Conference on Quantum Dots　2012/05/18
シングルリード量子ドット中の2電子状態を用いたスピン偏極検出

大塚朋廣, 杉原裕規, 米田淳, 小幡利顕, 勝本信吾, 樽茶清悟

日本物理学会　2012/03/26
大きなZeeman磁場差を有する二重量子ドットでの電子スピン共鳴実験

米田淳, 大塚朋廣, 高倉樹, 小幡利顕, 樽茶清悟

日本物理学会　2012/03/26
Speeding up single electron spin rotations in semiconductor quantum dots

Jun Yoneda, Tomohiro Otsuka, Tatsuki Takakura, Katsuharu Yoshida, Toshiaki Obata, Seigo Tarucha, Hong Lu, Christopher Palmstrøm, qual contributio

量子情報処理プロジェクト、量子サイバネティクス全体会議　2011/12/13
Speeding up single electron spin rotations in semiconductor quantum dots International-presentation

J. Yoneda, T. Otsuka, T. Takakura, K. Yoshida, T. Obata, S. Tarucha, H. Lu, C. Palmstrom, A. C. Gossard, qual contribution

International Workshop on Solid-State Quantum Computing　2011/12/12
Speed-up of Single Electron Spin Manipulation in Semiconductor Quantum Dots International-presentation

J. Yoneda, T. Otsuka, T. Takakura, K. Yoshida, T. Obata, S. Tarucha, ual, contri

International Workshop on Quantum Nanostructures and Nanoelectronics　2011/10
隣接量子ドット間ゼーマンエネルギー差の微小磁石設計による制御

米田淳, 大塚朋廣, 高倉樹, 小幡利顕, 樽茶清悟

日本物理学会　2011/09/24
Si/SiGe量子ドット構造のシミュレーションと作製

福岡佑二, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 小田俊理

応用物理学会　2011/09/01
Si/SiGe量子ドットにおけるショットキーゲート電極に対する考察

武田健太, 小幡利顕, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会　2011/03/28
横結合型量子ドットによる量子ドットのエネルギー準位スペクトル測定

桑原優樹, KIM Sunwoo, 大塚朋廣, 家泰弘, 勝本信吾

日本物理学会　2011/03/28
高速スピン回転操作のための大きな磁場差をもつ二重量子ドットデバイス

米田淳, 大塚朋廣, 高倉樹, 小幡利顕, 樽茶清悟

日本物理学会　2011/03/28
Si/SiGe量子ドット作製に向けたPdトップゲート動作点の低電圧化

福岡佑二, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 小田俊理

応用物理学関係連合講演会　2011/03/26
Speed-up of spin manipulation in semiconductor quantum dot

Tomohiro Otsuka, Jun Yoneda, Toshiaki Obata, Tatsuki Takakura, Kenta Takeda, Katsuharu Yoshida, Seigo Tarucha

量子情報処理プロジェクト報告会　2010/12
PdショットキーゲートによるSi/SiGe量子ドットの作製とその評価

武田健太, 小幡利顕, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会　2010/09/24
Lateral dot fabrication by using a MOS electric gate on SiGe hetero structure.

小幡利顕, 申潤錫, ロランドブルナ, 武田健太, 福岡佑二, 大塚朋廣, 小寺哲夫, 吉田勝治, 澤野憲太郎, 小田俊理, 白木靖寛, 樽茶清悟

日本物理学会　2010/09/24
Si/SiGe系2DEGのPdショットキーゲート制御による結合量子ドットの作製

福岡佑二, 小寺哲夫, 大塚朋廣, 武田健太, 小幡利顕, 吉田勝治, 澤野憲太郎, 内田建, 白木靖寛, 樽茶清悟, 小田俊理

応用物理学会　2010/09/14
微小磁石を用いた半導体量子ドット中の電子スピン操作

大塚朋廣, 米田淳, 小幡利顕, 高倉樹, 武田健太, Michel Pioro-Ladriere, 吉田勝治, 樽茶清悟

量子情報処理プロジェクトサマースクール　2010/08
Energy level spectroscopy of a quantum dot with a side‐coupled satellite dot International-presentation

Sunwoo Kim, Yuki Kuwabara, Tomohiro Otsuka, Yasuhiro Iye, Singo Katsumoto

International Conference on the Physics of Semiconductors　2010/07
Probing Local Electronic States in the Quantum Hall Regime with a Side Coupled Quantum Dot International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

International Symposium on Quantum Nanostructures and Spin-related Phenomena　2010/03
Probing local electronic states in the quantum Hall regime International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

International Symposium on Quantum Nanophotonics and Nanoelectronics　2009/11
横結合型量子ドットを用いた量子ホール状態の観測

大塚朋廣, 阿部英介, 家泰弘, 勝本信吾

日本物理学会　2009/09/26
Probing edge states in the quantum Hall regime with a side coupled quantum dot International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

International Symposium on Compound Semiconductors　2009/08
Detection of spin polarization in a quantum wire International-presentation

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

International Conference on Electronic Properties of Two-dimentional Systems　2009/07/21
側面結合量子ドットによるスピン偏極検出

大塚朋廣, 阿部英介, Amnon Aharony, Ora Entin-Wohlman, 都倉康弘, 勝本信吾

ナノ量子情報エレクトロニクス公開シンポジウム　2009/04/22
横結合型量子ドットを用いたスピン偏極の検出

大塚朋廣, 阿部英介, 家泰弘, 勝本信吾

日本物理学会　2009/03/30
Detection of spin polarization with a side coupled quantum dot International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

International Symposium on Nanoscale Transport and Technology　2009/01/22
側面結合した量子ドットによるスピン検出

勝本信吾, 大塚朋廣, 阿部英介, 家泰弘

物性科学領域横断研究会　2008/11
Excited state spectroscopy in side-coupled quantum dots International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

The IEEE Nanotechnology Materials and Devices Conference　2008/10/21
横結合型量子ドットにおける励起状態の観測

大塚朋廣, 阿部英介, 家泰弘, 勝本信吾

日本物理学会　2008/09/20
半導体量子ドットスピン状態の制御

大塚朋廣, 阿部英介, 勝本信吾

スピン流の創出と制御研究会　2008/02
T結合型量子ドットにおけるクーロン相互作用を利用した軌道占有制御

大塚朋廣, 阿部英介, 家泰弘, 勝本信吾

ナノ量子情報シンポジウム　2007/10/25
Control of shell filling with Coulomb interaction in quantum dots side-coupled to quantum wires International-presentation

T. Otsuka, E. Abe, Y. Iye, S. Katsumoto

International Symposium on Compound Semiconductors　2007/10/15
横結合型量子ドットにおけるクーロン相互作用

大塚朋廣, 阿部英介, 勝本信吾, 家泰弘

日本物理学会　2007/09/24
Potential dependent intra-dot Coulomb interaction in quantum dots side-coupled to quantum wires International-presentation

Tomohiro Otsuka, Eisuke Abe, Yasuhiro Iye, Shingo Katsumoto

International Conference on Electronic Properties of Two-dimentional Systems　2007/07
近藤状態の非局所制御

大塚朋廣, 勝本信吾, 家泰弘

日本物理学会　2007/03/20
Electronic states in quantum dots side-coupled to quantum wires International-presentation

Tomohiro Otsuka, Eisuke Abe, Shingo Katsumoto, Yasuhiro Iye

Frontiers in Nanoscale Science and Technology Workshop　2007/03
近藤状態の非局所制御

大塚朋廣, 勝本信吾, 家泰弘

半導体スピン工学の基礎と応用研究会　2006/12
Phase Information from Two-Terminal Conductance of Quantum Dot Systems International-presentation

T. Otsuka, H. Aikawa, M. Eto, G. L. Khym, K. Kang, Y. Iye, S. Katsumoto

International Conference on the Physics of Semiconductors　2006/07/28
2端子ABリングでの位相固定の破れについて

勝本信吾, 大塚朋廣, Amnon Aharony, Ora Entin-Wohlman

日本物理学会　2006/03/29
横結合型量子ドットを持つ量子細線の伝導特性

大塚朋廣, 勝本信吾, 家泰弘, G. L. Khym, Kicheon Kang

日本物理学会　2006/03/29

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Research Projects 11

プラズママテリアルズインフォマティクスが拓く完全カイラリティ制御ナノチューブ合成

加藤俊顕, 岩崎悠真, 大塚朋廣, 是常隆

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(A)

Institution: 東北大学

2023/04/01 - 2027/03/31
高品質酸化亜鉛微細構造における新奇量子電子物性解明

大塚朋廣, 小塚裕介

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(B)

Institution: 東北大学

2023/04/01 - 2026/03/31

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高品質な新しいヘテロ構造として、酸化亜鉛ヘテロ構造が作製されるようになっている。この構造では新しい独自の電子物性が現れることが期待される。そこで本研究では、高品質な酸化亜鉛材料作製、微細構造作製、精密伝導測定により、高品質酸化亜鉛微細構造における新奇量子電子物性の研究を行っている。本年度は特に、高品質酸化亜鉛ヘテロ構造を用いた微細構造の作製技術開発を中心に研究を行った。高品質酸化亜鉛ヘテロ構造は新しい材料であり、従来の半導体材料と異なるため、その微細加工において新しい技術開発が必要となる。特に半導体量子ドットやその複合系など、比較的複雑な微細構造試料を作製するため、新しい微細加工プロセスの開発を進めた。この際、研究チームメンバーがそれぞれ得意とする微細加工技術を組み合わせて活用することにより、高品質な酸化亜鉛微細構造の作製に成功した。また作製した高品質酸化亜鉛微細構造について、形状測定や電気伝導測定によりその基本特性を評価した。これらの評価結果をもとに、微細加工プロセスの最適化を行い、さらにこの技術を活用して新たな半導体量子ドットなどの微細構造の作製と評価を開始した。半導体量子ドットは電子を微小領域に閉じ込めるの構造であり、その内部では単電子帯電効果や量子準位の形成等が生じる。これらの現象について、電気伝導測定によりその特性を調べ、詳細な解析を進めている。これらの成果は、新材料の基礎物性解明の観点から有用であるとともに、高品質酸化亜鉛ヘテロ構造を活用した次世代デバイスの開発等に向けた重要なステップである。
機械学習による半導体量子ハードウェア最適化と応用

大塚朋廣

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 学術変革領域研究(A)

Institution: 東北大学

2023/04/01 - 2025/03/31

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機械学習やその他の情報科学の手法は、近年多くの学術分野に影響を及ぼしている。量子ハードウェア物理分野でも、これらの技術を用いることで従来にない新しい進展が期待されている。本研究では機械学習による半導体量子ハードウェア最適化と応用の研究を推進し、量子ハードウェアの状態推定、制御の自動化や、これを活用した量子ハードウェア、材料の物理解明等の研究を行っている。本年度は特に、機械学習を用いた半導体量子ハードウェアの状態推定手法の開発と改良を中心に研究を行った。半導体量子ハードウェアとして、電子を微小領域に閉じ込めた半導体量子ドットを用いて、その内部の電子の量子状態を活用する量子ハードウェアがある。これを用いて量子情報処理に向けた量子ビットシステム等を構成する際には、内部の電子状態の識別と制御が重要となる。従来、このプロセスは人間が行ってきたが、我々は畳み込みニューラルネットワークを用いた半導体量子ドットの電荷状態の自動推定を研究した。シミュレーションデータおよび実験データの双方について、その動作検証と解析を行った。さらに、Grad-CAMという可視化技術を用いて、そのプロセスを解析して従来の人間による判断と比較し、その結果を基に電荷状態推定器の改良を行った。またこのような機械学習手法と融合性の高いハードウェア制御技術についても研究を実施した。これらの成果は量子ハードウェア物理分野における情報科学手法の活用を進めるものであり、将来の大規模半導体量子ハードウェアの制御等に向けて役立つと期待される。
半導体量子ドットデバイスの放射線応答の調査と放射線検出器への利用

吉田斉, 岸本康宏, 大塚朋廣

Offer Organization: 日本学術振興会

System: 科学研究費助成事業挑戦的研究(萌芽)

Category: 挑戦的研究(萌芽)

Institution: 大阪大学

2022/06/30 - 2025/03/31
デコヒーレンスを活用した革新的量子技術の研究

大塚朋廣

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 挑戦的研究(萌芽)

Institution: 東北大学

2021/07/09 - 2024/03/31

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量子状態が壊れてしまうデコヒーレンスは、現状の現実世界の量子系では避けることができず、量子系の活用において問題となっている。しかし、もしこのデコヒーレンスをうまく利用できれば、有用な量子技術の要素として活用できる可能性もある。本研究では、操作性の良いデコヒーレンスを導入可能である半導体量子ドット系を用いて、デコヒーレンスについての物理解明を進め、これを活用した量子技術について研究している。本年度は特に半導体量子ドット系を用いた実験環境の整備、改良や、半導体量子ドット系の測定を中心に研究を行った。本研究では半導体量子ドットの中に形成される電圧等で人工的に制御可能な量子状態を実験系として利用する。このため、半導体微細加工技術を活用することにより、量子効果の発現する半導体量子ドット試料の作製を行った。また半導体量子ドット中の量子状態を明瞭に観測できる極低温環境における単一電子検出回路等の整備を行い、さらにその測定感度を向上させるための改良を行った。そしてこれを利用して半導体量子ドット系での量子状態の測定を行い、量子ドット内にトラップされた電子のスピンを利用した量子状態を観測した。また極低温環境下での高速電気信号制御系についても整備を行い、これを利用して半導体量子ドット中の量子状態の制御についても実施した。また半導体量子ドット系におけるデコヒーレンスに関するパラメータについても、その制御、評価を開始した。
Elucidation and control of hole spin dynamics in quantum structures

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (A)

Institution: Tokyo Institute of Technology

2020/04/01 - 2023/03/31
先進プラズマ活用1次元ナノカーボン材料の完全原子配列制御合成と革新的応用開拓

加藤俊顕, 大塚朋廣, 澁田靖

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 基盤研究(A)

Institution: 東北大学

2019/04/01 - 2023/03/31

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研究四年計画の二年度目にあたる今年度は、１次元ナノカーボン材料の原子レベル構造制御合成と応用に向けた研究を行い以下の成果を得た。第一に、初年度に立ち上げたその場観測プラズマCVDを用いることで、(6,5)ナノチューブの90%以上の超高純度合成を実現した。これはこれまで報告されている(6,5)ナノチューブの世界最高純度である。次年度以降では、プラズマ条件の最適化によりさらなる高純度化、及び(6,5)以外のカイラリティの選択合成を目指す。第二に、グラフェンナノリボンの量子デバイス応用に関して、本手法で合成したグラフェンナノリボンにおいて、量子化に伴う励起準位が明確に発現することを実証した。また、通常数百ミリKでしか安定に存在しない励起準位が２０K以上の高温条件でも観測可能であることを明らかとした。さらに、グラフェンナノリボン合成に用いるニッケルナノバー長とプラズマCVD合成条件を最適化することで、励起準位が観測できるグラフェンナノリボン量子ドットを高確率で合成することにも成功した。次年度以降は、高確率で励起準位観測が可能な本GNR量子ドットを用いることで、二重量子ドットを活用した量子演算の実証を試みる。第三に、1次元ナノカーボン材料と類似の原子層物質である遷移金属ダイカルコゲナイドに関して、一般的な気相―固相相転移に加え、液相―固相相転移による結晶成長が支配的であることを実験的に明らかにした。さらに、液相―固相相転移において、液相前駆体の化学ポテンシャルが核成長に与える効果を熱力学的観点から実験的に説明することに成功した。
スピン変換研究に向けた電気的超高速局所スピンプローブの開発と応用

大塚朋廣

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 新学術領域研究(研究領域提案型)

2017/04/01 - 2019/03/31

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本研究では半導体量子ドット等の半導体ナノ構造を活用することにより、固体ナノ構造中の局所スピン状態およびその時間変化にアクセスできる電気的高速局所スピンプローブを開発し、これを用いて固体ナノ構造中の局所スピン現象を調べた。本年度は特に、電気的高速局所スピンプローブ手法の改良、およびこのスピンプローブを用いた固体ナノ構造中の局所スピン状態ダイナミクスの測定解析を中心に行った。固体ナノ構造中でのスピン変換現象等をミクロに解明するためには、固体ナノ構造中の局所スピン状態に直接アクセスできる局所スピンプローブが有用となる。半導体量子ドット内にはスピンに依存した準位が存在し、この準位への電子のトンネルを調べることで、固体ナノ構造中の局所スピン状態を調べるプローブを実現することができる。またこのプローブを高周波測定技術と組み合わせることによって、ダイナミクスまで測定することが可能となる。この電気的高速局所スピンプローブを用いて、固体ナノ構造中の局所スピン状態およびそのダイナミクスを調べた。二次元電子ガスからなる電極と結合した半導体量子ドット中の電子スピンについて測定を行い、単一電子レベルで電荷状態とスピン状態の時間変化に差があることを明らかにした。この結果について、ミクロなモデルを構築して計算を行い、実験結果を再現することに成功した。また電気的高速局所スピンプローブの測定手法を活用することにより、他の固体ナノ構造中の局所スピン状態の観測と操作の研究についても貢献した。
高速量子プローブを用いた微小系の電子輸送ゆらぎの研究

大塚朋廣

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 新学術領域研究(研究領域提案型)

Institution: 国立研究開発法人理化学研究所

2016/04/01 - 2018/03/31

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本研究では、半導体微細構造を活用した微小系を用いて、微小系における電子輸送、ゆらぎ、ダイナミクスの測定、解明を行った。本年度は特に高速量子プローブを活用した微小系における局所電子状態のダイナミクス測定、量子微小系の局所電子状態測定を中心に実施した。微小系における局所電子状態およびそのダイナミクスは、物性科学等の基礎科学やエレクトロニクスデバイス等の応用の両面から重要となっている。この微小系における局所電子状態について、高速量子プローブを使って引き続き測定し、またその結果の解析を行った。半導体量子ドットからなる開放微小系について、局所電子状態の測定を実施したところ、局所電子状態が電極との結合に依存してマイクロ秒程度の時間スケールで変化する様子を観測した。さらに半導体量子ドット中の局所電子状態の時間変化の詳細を調べたところ、トンネルの低次の過程と、高次の過程による電子状態変化をミクロな観点から解明することができた。また高速量子プローブで開発してきた測定手法は、古典微小系だけでなく量子現象が発現する量子微小系に対しても適用可能である。量子微小系は量子エレクトロニクス、量子情報処理等に向けて近年、注目を集めており、本研究では高速量子プローブの技術を活用して量子微小系における局所電子状態測定を行った。この結果、量子ドット内状態の高精度操作、多重量子ドットにおける電子状態操作の実現等に貢献した。
Probing local electronic and spin states in semiconductor microstructures by single-lead quantum dots

OTSUKA Tomohiro

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Young Scientists (B)

Institution: The Institute of Physical and Chemical Research

2013/04/01 - 2015/03/31

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We measured local electronic and spin states in semiconductor microstructures by probes utilizing quantum microstructures. We analyzed experimental results on the measurement of energy relaxation in quantum Hall edge states by quantum point contacts and revealed a possible mechanism of the probe operation. We developed new fast local electronic probes, which can access dynamics of local electronic and spin states, by using the quantum dot probes and high frequency measurement techniques. We applied these new probes to measure local electronic states in quantum dots and confirmed the operation and examined the characteristics.
Study of quantum coherence in multiple system utilizing multi single-lead quantum dots

OTSUKA Tomohiro

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Research Activity Start-up

Institution: The University of Tokyo

2010 - 2011

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We have demonstrated experiments relating multiple quantum systems utilizing semiconductor nano structures. We measured relaxation in quantum Hall edge states, which are important components of multiple quantum systems, with quantum point contacts and discussed about the relaxation mechanisms. We also developed a new method to detect local spin polarization in semiconductor nano structures, which is essential in spin related quantum systems, by using single-lead quantum dots and confirmed its operation. With this new method, we probed local spin polarization formed in quantum Hall edge states.

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Social Activities 7

実験人工量子力学と量子デバイス

東北大学オープンキャンパス

2023/07/26 - 2023/07/27
小さな世界の不思議な性質：実験人工量子力学

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2022/10/08 - 2022/10/09
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Media Coverage 21

機械学習を活用し、量子ドットの電圧を自動的に調整する手法を実証 ─大規模量子コンピューターの調整自動化に期待─

東北大学プレスリリース

2026/03/06

Type: Internet
半導体コロイド量子ドット環境適合性材料で評価電子デバイスへの応用期待

科学新聞

2026/01/16

Type: Newspaper, magazine
単一コロイド量子ドットで電気的なスピン検出と制御に成功～環境調和型材料から拓く量子・スピントロニクス技術～

東北大学プレスリリース

2026/01/06

Type: Internet
東北大、酸化亜鉛で三重量子ドット形成

日刊工業新聞

2025/11/03

Type: Internet
酸化亜鉛デバイスで量子ドット形成東北大、量子コン開発へ向け進展期待

科学新聞

2025/10/31

Type: Newspaper, magazine
酸化亜鉛における電界制御三重量子ドット形成と量子セルオートマトン効果を観測

日本経済新聞

2025/10/23

Type: Internet
Controlling Triple Quantum Dots in a Zinc Oxide Semiconductor

Tohoku University Research News

2025/10/23

Type: Internet
東北大、ベイズの定理で量子ドット電荷推定量子計算基礎技術に

日刊工業新聞

2025/04/14

Type: Internet
New Bayesian Method Enables Rapid Detection of Quantum Dot Charge States

Tohoku University Research News

2025/04/09

Type: Internet
東北大、量子ドットの電荷状態を高速に検出する解析手法を開発

日本経済新聞

2025/04

Type: Internet
A Pathway Towards New Quantum Devices: Electrically Defined Quantum Dots in Zinc Oxide

Tohoku University Research News

2024/11/08

Type: Internet
Visual Explanations of Machine Learning Models to Estimate Charge States in Quantum Dots

Tohoku University Research News

2024/04/22

Type: Internet
東北大、機械学習活用による量子ドットの電荷状態推定と可視化に基づく更なる性能改善を実証

日本経済新聞

2024/04/22

Type: Internet
電気伝導の詳細評価単一コロイド量子ドット東北工大など

日刊工業新聞

2023/12/18

Type: Newspaper, magazine
単一コロイド量子ドットで電気伝導の評価と制御に成功

東北大学プレスリリース

2023/12/01

Type: Internet
東北工業大・東大・東北大・理研・東京農工大、単一コロイド量子ドットで電気伝導の評価と制御に成功

日本経済新聞

2023/12/01

Type: Internet
東北大、高速量子ビット読み出し手法をグラフェンで実現

日本経済新聞

2023/07/18

Type: Internet
高速量子ビット読み出し手法をグラフェンで実現 ─グラフェン量子コンピュータへ期待─

東北大プレスリリース

2023/07/18

Type: Internet
東北大、グラフェンナノリボン上で量子ドット作成量子デバイス作製に応用

日刊工業新聞

2023/01/09

Type: Newspaper, magazine
東北大、グラフェン量子ドットデバイスの集積化合成技術を開発

日本経済新聞

2023/01/06

Type: Internet
グラフェン量子ドットデバイスの集積化合成技術を開発 ― 次世代高性能量子コンピュータの実現に期待 ―

東北大プレスリリース

2023/01/06

Type: Internet

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