Koike, Tatsuhiko

写真a

Affiliation

Faculty of Science and Technology, Department of Physics （Yagami）

Position

Assistant Professor/Senior Assistant Professor

Related Websites

External Links
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Career 【 Display / hide 】

  • 1993.04
    -
    1996.03

    Tokyo Institute of Technology, 物理学科, JSPS postdoctoral fellow

  • 1993.04
    -
    1996.03

    Tokyo Institute of Technology, 物理学科, JSPS postdoctoral fellow

  • 1996.04
    -
    2006.03

    Department of Physics, Keio University, 物理学科, 助手

  • 1996.04
    -
    2006.03

    Department of Physics, Keio University, 物理学科, 助手

  • 2000.02
    -
    2001.03

    University of Maryland, JSPS postdoctoral fellow

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Academic Background 【 Display / hide 】

  • 1991.03

    The University of Tokyo, Faculty of Science, Department of Physics

  • 1991.03

    The University of Tokyo, Faculty of Science, Department of Physics

    University, Graduated

  • 1993.03

    Tokyo Institute of Technology, Graduate School, Division of Science and Engineeri, 物理学

  • 1993.03

    Tokyo Institute of Technology, Graduate School, Division of Science and Engineeri, 物理学

    Graduate School, Completed, Master's course

  • 1996.03

    Tokyo Institute of Technology, Graduate School, Division of Science and Engineeri, 物理学

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Academic Degrees 【 Display / hide 】

  • 修士（理学）, Tokyo Institute of Technology, Coursework, 1993.03

  • 博士（理学）, Tokyo Institute of Technology, Coursework, 1996.03

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Research Areas 【 Display / hide 】

  • Natural Science / Semiconductors, optical properties of condensed matter and atomic physics (Atomic/Molecular/Quantum Electronics, Plasma)

  • Natural Science / Semiconductors, optical properties of condensed matter and atomic physics (Atomic/Molecular/Quantum Electronics, Plasma)

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics (Elementary Particle/Atomic Nucleus/Cosmic Ray/Space Physics)

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics (Elementary Particle/Atomic Nucleus/Cosmic Ray/Space Physics)

  • Informatics / Theory of informatics (Fundamental Informatics)

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Books 【 Display / hide 】

  • Singularities in Geometry and Topology

    KOIKE TATSUHIKO, European Mathematical Society, 2012

    Scope: 51-69

  • 爆発と凝集

    原隆, 古池達彦, 東京大学出版会, 2006.02

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Papers 【 Display / hide 】

  • Nambu-Goto strings with a null symmetry and contact structure

    Hiroshi Kozaki, Tatsuhiko Koike, Yoshiyuki Morisawa and Hideki Ishihara

    Physical Review D （American Physical Society)  108   084069 2023.08

    Research paper (scientific journal), Joint Work, Accepted

  • Quantum brachistochrone

    Tatsuhiko Koike

    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences （Royal Society Publishing)  380 （ 2239 ）  2022.12

    Lead author, Last author, Corresponding author,  ISSN  1364503X

    　View Summary

    Quantum brachistochrone (QB) is a quantum analogue of classical brachistochrone (shortest path). It is a solution to the following problem: How can we perform a desired quantum operation (or obtain a desired final quantum state) most quickly, by a time-dependent Hamiltonian subject to given constraints? Finding QB is a fundamental problem in quantum mechanics in its own right. Moreover, it will be useful in the study of quantum information and quantum engineering, such as quantum speed limits and implementations of quantum computers. A general framework for finding QBs, called QB formalism, has been developed. It is based on Pontryagin's maximum principle. We review the basics of the QB formalism, give simple examples, and briefly discuss some related studies. This article is part of the theme issue 'Shortcuts to adiabaticity: theoretical, experimental and interdisciplinary perspectives'.

  • A general formulation of time-optimal quantum control and optimality of singular protocols

    Wakamura Hiroaki, Koike Tatsuhiko

    NEW JOURNAL OF PHYSICS （New Journal of Physics)  22 （ 7 ）  2020.07

    ISSN  1367-2630

    　View Summary

    We present a general theoretical framework for finding the time-optimal unitary evolution of the quantum systems when the Hamiltonian is subject to arbitrary constraints. Quantum brachistochrone (QB) is such a framework based on the variational principle, whose drawback is that it only deals with equality constraints. While inequality constraints can be reduced to equality ones in some situations, they usually cannot, especially when a drift field, an uncontrollable part, is present in the Hamiltonian. We first develop a framework based on Pontryagin's maximum principle (MP) in order to deal with inequality constraints as well. The new framework contains QB as a special case, and their detailed correspondence is given. Second, we address the problem of singular controls, which satisfy MP trivially so as to cause a trouble in determining the optimal protocol. To overcome this difficulty, we derive an additional necessary condition for a singular protocol to be optimal by applying the generalized Legendre-Clebsch condition. Third, we discuss general relations among the drift, the singular controls, and the inequality constraints. Finally, we demonstrate how our framework and results work in some examples. We also discuss the physical meaning of singular controls.

  • Cohomogeneity-one-string integrability of spacetimes

    Morisawa Y, Hasegawa S, Koike T, Ishihara H

    Classical and Quantum Gravity （Classical and Quantum Gravity)  36 （ 15 ）  2019.07

    Joint Work,  ISSN  02649381

    　View Summary

    © 2019 IOP Publishing Ltd. A classical string whose world sheet shares a one-dimensional symmetry with the spacetime is called cohomogeneity-one (C1). We propose C1-string integrability, i.e. integrability of all C1 strings in the spacetime, as a class of hidden symmetry of a spacetime. The C1 string may probe symmetry which is not probed by a particle. We present a simple, systematic procedure for finding constants of motion of a C1 string and examining C1 string integrability of a spacetime. We apply the framework to some physically important spacetimes such as AdS5, AdS5 × S5, and AdS5 × Tp,q. C1 strings and C1-string integrability may be useful for a prior examination of general string integrability of a highly symmetric spacetime since, among the examples above, all C1 string integrable spacetimes are string-integrable, and the previously obtained chaotic string solutions in those or other spacetimes are of class C1.

  • Disturbance by optimal discrimination

    Ryuitiro Kawakubo and Tatsuhiko Koike

    Physical Review A （American Physical Society)  97 （ 3 ） 032102 (5pp) 2018.03

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  24699926

    　View Summary

    © 2018 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. We discuss the disturbance by measurements which unambiguously discriminate between given candidate states. We prove that such an optimal measurement necessarily changes distinguishable states indistinguishable when the inconclusive outcome is obtained. The result was previously shown by Chefles [Phys. Lett. A 239, 339 (1998)PYLAAG0375-960110.1016/S0375-9601(98)00064-4] under restrictions on the class of quantum measurements and on the definition of optimality. Our theorems remove these restrictions and are also applicable to infinitely many candidate states. Combining with our previous results, one can obtain concrete mathematical conditions for the resulting states. The method may have a wide variety of applications in contexts other than state discrimination.

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Presentations 【 Display / hide 】

  • Quantum brachistochrone and Pontryagin's maximum principle

    Tatsuhiko Koike

    重力と量子で紡ぐ宇 宙 (公共の宿 しきぶ温泉 湯楽里) , 

    2023.08
    , 

    Oral presentation (invited, special), 斉田 浩見、樽家 篤史、野田 宗佑、吉野 裕高、柳 哲文

  • 等質余次元1物体から量子最速曲線まで

    古池 達彦

    相対論と重力研究の現在，過去・未来 (大阪市立大学) , 

    2022.03
    , 

    Oral presentation (invited, special)

  • A generalization of quantum brachistochrone

    Hiroaki Wakamura, Tatsuhiko Koike

    第21回「特異点と時空、および関連する物理」研究会 (秋田市) , 

    2019.12
    , 

    Oral presentation (general), 特異点研究会組織委員会

  • 量子系での時間最適制御の一般論と特異的な制御

    若村浩明, 川久保龍一郎, 古池達彦

    日本物理学会2019年秋季大会 (岐阜大学柳戸キャンパス) , 

    2019.09
    , 

    Oral presentation (general), 日本物理学会

  • Time-optimal unitary evolution and singular control

    Hiroaki Wakamura and Tatsuhiko Koike

    Gordon Research Conference on Quantum control of Light and Matter (Coherent Control of Quantum Systems with Increasing Complexity) (Newport, USA) , 

    2019.08
    , 

    Poster presentation

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

  • 時間最適量子制御の基礎理論と特異制御に関する研究

    2020.04
    -
    2023.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, 古池 達彦, Grant-in-Aid for Scientific Research (C), Principal investigator

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Awards 【 Display / hide 】

  • Teshima Memorial Doctoral Thesis Award

    KOIKE TATSUHIKO, 1996.03, 手島工業教育資金団, Renormalization group analysis of critical behaviour in gravitational collapse

    Type of Award： Award from publisher, newspaper, foundation, etc.

  • Teshima Memorial Doctoral Thesis Award

    HKOIKE TATSUHIKO, HR, 1996.03, 手島工業教育資金団, Renormalization group analysis of critical behaviour in gravitational collapse

    Type of Award： Award from publisher, newspaper, foundation, etc.

  • Teshima Memorial Doctoral Thesis Award

    KOIKE TATSUHIKO, 1996.03, 手島工業教育資金団, Renormalization group analysis of critical behaviour in gravitational collapse

    Type of Award： Award from publisher, newspaper, foundation, etc.

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Courses Taught 【 Display / hide 】

  • THEORY OF RELATIVITY

    2024

  • PHYSICS SEMINAR 4

    2024

  • PHYSICS EXERCISE 2

    2024

  • PHYSICS C

    2024

  • LITERATURE OF PHYSICS

    2024

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Courses Previously Taught 【 Display / hide 】

  • LITERATURE OF PHYSICS

    Keio University

    2023.04
    -
    2024.03

  • THEORY OF RELATIVITY

    Keio University

    2023.04
    -
    2024.03

  • PHYSICS C

    Keio University

    2023.04
    -
    2024.03

  • PHYSICS EXERCISE 2

    Keio University

    2023.04
    -
    2024.03

  • INDEPENDENT STUDY ON FUNDAMENTAL SCIENCE AND TECHNOLOGY

    Keio University

    2023.04
    -
    2024.03

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Memberships in Academic Societies 【 Display / hide 】

  • 日本物理学会新著紹介小委員会, 

    2007.11
    -
    2009.10

  • 日本物理学会新著紹介小委員会, 

    2007.11
    -
    2009.10
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Committee Experiences 【 Display / hide 】

  • 2007.11
    -
    2009.10

    Committee Member, 日本物理学会新著紹介小委員会

  • 2007.11
    -
    2009.10

    委員, 日本物理学会新著紹介小委員会

  • 2007.11
    -
    2009.10

    Committee Member, 日本物理学会新著紹介小委員会

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