Yamamoto, Naoki

写真a

Affiliation

Faculty of Science and Technology, Department of Applied Physics and Physico-Informatics (Yagami)

Position

Professor

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Career 【 Display / hide 】

  • 2003.04
    -
    2007.03

    日本学術振興会, 特別研究員

  • 2004.07
    -
    2007.02

    California Institute of Technology, Department of Physics, Postdoctral Fellow

  • 2007.04
    -
    2008.03

    Australian National University, Department of Engineering, Postdoctral Fellow

  • 2008.04
    -
    2011.03

    慶應義塾大学, 理工学部・物理情報工学科, 専任講師

  • 2011.04
    -
    2019.03

    慶應義塾大学, 理工学部・物理情報工学科, 准教授

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Academic Background 【 Display / hide 】

  • 1999.03

    The University of Tokyo, Faculty of Engineering, 計数工学科

    University, Graduated

  • 2004.03

    The University of Tokyo, 情報理工学系研究科, システム情報学専攻

    Graduate School, Completed, Doctoral course

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Academic Degrees 【 Display / hide 】

  • 情報理工学, The University of Tokyo, Coursework, 2004.03

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Research Areas 【 Display / hide 】

  • Natural Science / Applied mathematics and statistics (量子計算、量子情報)

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Control and system engineering (量子制御)

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Research Keywords 【 Display / hide 】

  • Quantum control

  • Quantum information

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Books 【 Display / hide 】

  • Linear Dynamical Quantum Systems: Analysis, Synthesis, and Control

    H. I. Nurdin and N. Yamamoto, Springer, 2017.05

  • 複素関数論の基礎

    YAMAMOTO Naoki, 裳華房, 2015.11

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Papers 【 Display / hide 】

  • Natural quantum reservoir computing for temporal information processing

    Suzuki Y., Gao Q., Pradel K.C., Yasuoka K., Yamamoto N.

    Scientific Reports (Scientific Reports)  12 ( 1 )  2022.12

    　View Summary

    Reservoir computing is a temporal information processing system that exploits artificial or physical dissipative dynamics to learn a dynamical system and generate the target time-series. This paper proposes the use of real superconducting quantum computing devices as the reservoir, where the dissipative property is served by the natural noise added to the quantum bits. The performance of this natural quantum reservoir is demonstrated in a benchmark time-series regression problem and a practical problem classifying different objects based on temporal sensor data. In both cases the proposed reservoir computer shows a higher performance than a linear regression or classification model. The results indicate that a noisy quantum device potentially functions as a reservoir computer, and notably, the quantum noise, which is undesirable in the conventional quantum computation, can be used as a rich computation resource.

  • Speed limits for two-qubit gates with weakly anharmonic qubits

    Ashhab S., Yoshihara F., Fuse T., Yamamoto N., Lupascu A., Semba K.

    Physical Review A (Physical Review A)  105 ( 4 )  2022.04

    ISSN  24699926

    　View Summary

    We consider the implementation of two-qubit gates when the physical systems used to realize the qubits possess additional quantum states in the accessible energy range. We use optimal control theory to determine the maximum achievable gate speed for two-qubit gates in the qubit subspace of the many-level Hilbert space, and we analyze the effect of the additional quantum states on the gate speed. We identify two competing mechanisms. On one hand, higher energy levels are generally more strongly coupled to each other. Under suitable conditions, this stronger coupling can be utilized to make two-qubit gates significantly faster than the reference value based on simple qubits. On the other hand, a weak anharmonicity constrains the speed at which the system can be adequately controlled: according to the intuitive picture, faster operations require stronger control fields, which are more likely to excite higher levels in a weakly anharmonic system, which in turn leads to faster decoherence and uncontrolled leakage outside the qubit space. To account for this constraint, we modify the pulse optimization algorithm to avoid pulses that lead to appreciable population of the higher levels. In this case, we find that the presence of the higher levels can lead to a significant reduction in the maximum achievable gate speed. We also compare the optimal-control gate speeds with those obtained using the cross-resonance or selective-darkening gate protocol. We find that this protocol, with some parameter optimization, can be used to achieve a relatively fast implementation of the controlled-NOT gate. These results can help the search for optimized gate implementations in realistic quantum computing architectures, such as those based on superconducting circuits. They also provide guidelines for desirable conditions on anharmonicity that would allow optimal utilization of the higher levels to achieve fast quantum gates.

  • Grover search revisited: Application to image pattern matching

    Tezuka H., Nakaji K., Satoh T., Yamamoto N.

    Physical Review A (Physical Review A)  105 ( 3 )  2022.03

    ISSN  24699926

    　View Summary

    The landmark Grover algorithm for amplitude amplification serves as an essential subroutine in various types of quantum algorithms, with guaranteed quantum speedup in query complexity. However, there has been no proposal to realize the original motivating application of the algorithm, i.e., the database search or more broadly the pattern matching in a practical setting, mainly due to the technical difficulty in efficiently implementing the data loading and amplitude amplification processes. In this paper, we propose a quantum algorithm that approximately executes the entire Grover database search or pattern matching algorithm. The key idea is to use the recently proposed approximate amplitude encoding method on a shallow quantum circuit, together with the easily implementable inversion-test operation for realizing the projected quantum state having similarity to the query data, followed by the amplitude amplification operation that is independent to the target data index. We provide a thorough demonstration of the algorithm in the problem of image pattern matching.

  • Noisy quantum amplitude estimation without noise estimation

    Tanaka T., Uno S., Onodera T., Yamamoto N., Suzuki Y.

    Physical Review A (Physical Review A)  105 ( 1 )  2022.01

    ISSN  24699926

    　View Summary

    Many quantum algorithms contain an important subroutine - the quantum amplitude estimation. As the name implies, this is essentially the parameter estimation problem and thus can be handled via the established statistical estimation theory. However, this problem has an intrinsic difficulty that the system, i.e., the real quantum computing device, inevitably introduces unknown noise; the probability distribution model then has to incorporate many nuisance noise parameters, resulting that the construction of an optimal estimator becomes inefficient and difficult. For this problem we apply the theory of nuisance parameters (more specifically, the parameter orthogonalization method) to precisely compute the maximum likelihood estimator for only the target amplitude parameter by removing the other nuisance noise parameters. That is, we can estimate the amplitude parameter without estimating the noise parameters. We validate the parameter orthogonalization method in a numerical simulation and study the performance of the estimator in the experiment using a real superconducting quantum device.

  • Applications of quantum computing for investigations of electronic transitions in phenylsulfonyl-carbazole TADF emitters

    Gao Q., Jones G.O., Motta M., Sugawara M., Watanabe H.C., Kobayashi T., Watanabe E., Ohnishi Y.y., Nakamura H., Yamamoto N.

    npj Computational Materials (npj Computational Materials)  7 ( 1 )  2021.12

    　View Summary

    A quantum chemistry study of the first singlet (S1) and triplet (T1) excited states of phenylsulfonyl-carbazole compounds, proposed as useful thermally activated delayed fluorescence (TADF) emitters for organic light emitting diode (OLED) applications, was performed with the quantum Equation-Of-Motion Variational Quantum Eigensolver (qEOM-VQE) and Variational Quantum Deflation (VQD) algorithms on quantum simulators and devices. These quantum simulations were performed with double zeta quality basis sets on an active space comprising the highest occupied and lowest unoccupied molecular orbitals (HOMO, LUMO) of the TADF molecules. The differences in energy separations between S1 and T1 (ΔEST) predicted by calculations on quantum simulators were found to be in excellent agreement with experimental data. Differences of 17 and 88 mHa with respect to exact energies were found for excited states by using the qEOM-VQE and VQD algorithms, respectively, to perform simulations on quantum devices without error mitigation. By utilizing state tomography to purify the quantum states and correct energy values, the large errors found for unmitigated results could be improved to differences of, at most, 4 mHa with respect to exact values. Consequently, excellent agreement could be found between values of ΔEST predicted by quantum simulations and those found in experiments.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Reviews, Commentaries, etc. 【 Display / hide 】

  • 連続時間カルマンフィルタと量子状態推定

    山本 直樹

    計測自動制御学会誌 56 ( 9 ) 662 - 667 2017.09

    Article, review, commentary, editorial, etc. (scientific journal)

  • 量子フィードバック制御のための推定論とその応用

    山本 直樹

    京都大学数理解析研究所講究録 1834 ( 5 ) 96 - 108 2013.05

    Article, review, commentary, editorial, etc. (bulletin of university, research institution), Single Work

  • 量子フィードバック制御の数理

    山本 直樹

    数理科学 585   21 - 27 2012.03

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Single Work

  • 確率微分方程式の基礎

    山本 直樹

    計測と制御 50 ( 11 ) 937-943 2011.11

    Article, review, commentary, editorial, etc. (scientific journal), Single Work

  • 量子力学と確率システム理論

    山本 直樹

    計測と制御 50 ( 11 ) 993-999 2011.11

    Article, review, commentary, editorial, etc. (scientific journal), Single Work

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Presentations 【 Display / hide 】

  • Quantum op-amp and functionalities

    N. Yamamoto

    APS March Meeting (Los Angeles, California, USA) , 

    2018.03
    , 

    Oral presentation (general), APS

  • 散逸下における量子状態制御の限界

    小林幸一、山本直樹

    第37回量子情報技術研究会, 

    2017.11
    , 

    Oral presentation (general)

  • 多段量子フィードバック増幅器の感度解析

    横寺裕、山本直樹

    第36回量子情報技術研究会, 

    2017.05
    , 

    Poster presentation

  • 散逸下における量子状態制御の限界

    小林幸一、山本直樹

    第35回量子情報技術シンポジウム, 

    2016.11
    , 

    Poster presentation

  • LQG制御による量子スクイズド状態の角度揺らぎ抑制

    黒柳亮介、山本直樹

    第35回量子情報技術シンポジウム (高エネルギー加速器研究機構) , 

    2016.11
    , 

    Poster presentation

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • 量子ソフトウェア

    2018.10
    -
    Present

    科学技術振興機構, MEXT - Quantum Leap Flagship Program(MEXT Q-LEAP), Research grant, Principal investigator

  • フィードバック増幅による量子機能創出

    2016.10
    -
    2020.03

    科学技術振興機構, Precursory Research for Embryonic Science and Technology, Research grant, Principal investigator

  • システム制御理論に基づく量子状態変換法の設計理論

    2015.04
    -
    2018.03

    日本学術振興会, Grant-in-Aid for Scientific Research, Research grant, Principal investigator

  • デコヒーレンスフリー量子情報処理のためのシステム制御理論

    2012.04
    -
    2015.03

    日本学術振興会, Grant-in-Aid for Scientific Research, Research grant, Principal investigator

  • 線形量子ネットワークのフィードバック制御理論

    2009.04
    -
    2012.03

    日本学術振興会, Grant-in-Aid for Scientific Research, Research grant, Principal investigator

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Awards 【 Display / hide 】

  • Outstanding Reviewer Award

    2018.02, IOP

  • エレクトロニクスソサイエティ活動功労表彰

    2018.02, 電子情報通信学会

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Courses Taught 【 Display / hide 】

  • PRESENTATION TECHNIQUE

    2025

  • MATHEMATICS FOR APPLIED PHYSICS (A)

    2025

  • MATHEMATICAL ENGINEERING FOR QUANTUM MECHANICS

    2025

  • INDEPENDENT STUDY ON FUNDAMENTAL SCIENCE AND TECHNOLOGY

    2025

  • GRADUATE RESEARCH ON FUNDAMENTAL SCIENCE AND TECHNOLOGY 2

    2025

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Courses Previously Taught 【 Display / hide 】

  • 物理情報数学A

    Keio University

    2014.04
    -
    2015.03
    , 

    Spring Semester, Lecture, Lecturer outside of Keio, 1h

    複素関数論

  • 応用確率論

    Keio University

    2014.04
    -
    2015.03
    , 

    Autumn Semester, Lecture, Within own ｆaculty, 1h

    確率・確率過程論

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Committee Experiences 【 Display / hide 】

  • 2013.04
    -
    Present

    量子情報技術時限付専門委員, 電子情報通信学会エレクトロニクスソサエティ

    　View Remarks

    2015年 4月 ~ 2017年3月 の２年間、幹事

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