Updated on 2026/03/31

写真a

 
OKUNISHI KOUICHI
 
Organization
Graduate School of Science Department of Physics Professor
School of Science Department of Physics
Title
Professor
Affiliation
Institute of Science
Affiliation campus
Sugimoto Campus

Position

  • Graduate School of Science Department of Physics 

    Professor  2025.04 - Now

  • School of Science Department of Physics 

    Professor  2025.04 - Now

Degree

  • 博士(理学) （ Osaka University ）

Research Areas

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics  / テンソルネットワーク、量子エンタングルメント

  • Natural Science / Magnetism, superconductivity and strongly correlated systems  / 量子スピン系

Research Interests

  • Magnetism

  • Statistical Physics

  • 磁性

  • 統計物理学

  • quantum information physics

Research subject summary

  • 量子情報にもとづく量子多体系の理論的研究

  • 量子スピン系の理論的研究

Professional Memberships

  • 日本物理学会

  • 電子スピンサイエンス学会

  • THE SOCIETY OF ELECTRON SPIN SCIENCE AND TECHNOLOGY

  • 日本物理学会

Awards

  • 日本物理学会領域３若手奨励賞

Job Career (off-campus)

  • Osaka Metropolitan University   Graduate School of Science Department of Physics

    2025.04 - Now

  • Niigata University

    2011.02 - 2025.03

  • - Niigata University, Research assistant

    2000

Education

  • Osaka University   The second semester of doctoral program   Graduated/Completed

    1996.04 - 1999.03

Papers

  • Translational Symmetry Broken Magnetization Plateau of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>S</mml:mi> <mml:mo>=</mml:mo> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mn>2</mml:mn> </mml:mfrac> </mml:math> Anisotropic Spin Ladder with Ferromagnetic Rung Interaction

    Tôru Sakai, Koki Doi, Kiyomi Okamoto, Kouichi Okunishi, Masaru Hashimoto, Tomoki Houda, Rito Furuchi, Hiroki Nakano

    Journal of Physics: Conference Series   3161 ( 1 )   012004 - 012004   2026.01（ ISSN:1742-6588 ） （ eISSN:1742-6596 ）

    　More details

    Publishing type：Research paper (scientific journal)  

    Abstract

    The magnetization process of the S = 1/2 anisotropic spin ladder with the ferromagnetic rung interaction is investigated using the numerical diagonalization of finite-size clusters. It is found that the translational symmetry broken magnetization plateau would appear at half the saturation magnetization, when the competing anisotropies are sufficiently large. The phase diagram with respect to the anisotropies and several magnetization curves are presented.

    DOI： 10.1088/1742-6596/3161/1/012004

    Other URL： https://iopscience.iop.org/article/10.1088/1742-6596/3161/1/012004/pdf

  • Quantum Phase Transition and Magnetic Excitation in the S = 1/2 Ising-like Antiferromagnetic Chain CsCoCl3 in Transverse Magnetic Fields

    Shojiro Kimura, Hiroaki Onishi, Yasuo Narumi, Kouichi Okunishi, Masayuki Hagiwara, Koichi Kindo, Hikomitsu Kikuchi

    Journal of the Physical Society of Japan   2025.12

    　More details

    Publishing type：Research paper (scientific journal)  

    DOI： 10.7566/JPSJ.94.124703

  • Improving the accuracy of the tree-tensor network approach by optimization of network structure Reviewed

    Toshiya Hikihara, Hiroshi Ueda, Kouichi Okunishi, Kenji Harada, Tomotoshi Nishino

    Physical Review B   2025.10

    　More details

    Publishing type：Research paper (scientific journal)  

    DOI： 10.1103/ljj8-tkpc

  • Tensor Renormalization Group Study of the 3D SU(2) and SU(3) Gauge Theories with the Reduced Tensor Network Formulation Reviewed

    Atis Yosprakob, Kouichi Okunishi

    Progress of Theoretical and Experimental Physics   2025.03

    　More details

    Publishing type：Research paper (scientific journal)  

    DOI： 10.1093/ptep/ptaf028

  • Holographic Analysis of Boundary Correlation Functions for the Hyperbolic-Lattice Ising Model Reviewed

    Kouichi Okunishi, Tomotoshi Nishino

    Progress of Theoretical and Experimental Physics   2024.09

    　More details

    Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

    DOI： 10.1093/ptep/ptae137

  • Visualization of Entanglement Geometry by Structural Optimization of Tree Tensor Network

    Toshiya Hikihara, Hiroshi Ueda, Kouichi Okunishi, Kenji Harada, Tomotoshi Nishino

    arXiv:2401.16000   2024.01

    　More details

    Publishing type：Research paper (international conference proceedings)  

    DOI： 10.48550/arXiv.2401.16000

  • Statistical mechanics approach to the holographic renormalization group: Bethe lattice Ising model and p-adic AdS/CFT Reviewed

    Kouichi Okunishi, Tadashi Takayanagi

    Progress of Theoretical and Experimental Physics   2024.01

    　More details

    Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

    DOI： 10.1093/ptep/ptad156

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MISC

  • Clifford Circuits Augmented Grassmann Matrix Product States OA

    Atis Yosprakob, Wei-Lin Tu, Tsuyoshi Okubo, Kouichi Okunishi, Donghoon Kim

    2025.10

    　More details

    Recent advances in combining Clifford circuits with tensor network (TN)
    states have shown that classically simulable disentanglers can significantly
    reduce entanglement, mitigating the bond-dimension bottleneck in TN
    simulations. In this work, we develop a variational TN framework based on
    Grassmann tensor networks, which natively encode fermionic statistics while
    preserving locality. By incorporating locally defined Clifford circuits within
    the fermionic formalism, we simulate benchmark models including the
    tight-binding and $t$-$V$ models. Our results show that Clifford disentangling
    removes the classically simulable component of entanglement, leading to a
    reduced bond dimension and improved accuracy in ground-state energy estimates.
    Interestingly, imposing the natural Grassmann-evenness constraint on the
    Clifford circuits significantly reduces the number of disentangling gates, from
    720 to just 32, yielding a far more efficient implementation. These findings
    highlight the potential of Clifford-augmented Grassmann TNs as a scalable and
    accurate tool for studying strongly correlated fermionic systems, particularly
    in higher dimensions.

    Other URL： http://arxiv.org/pdf/2510.04164v1

  • Holographic Aspects of Dynamical Mean-Field Theory OA

    Kouichi Okunishi, Akihisa Koga

    2025.09

    　More details

    Dynamical mean-field theory (DMFT) is one of the most standard theoretical
    frameworks for addressing strongly correlated electron systems. Meanwhile, the
    concept of holography, developed in the field of quantum gravity, provides an
    intrinsic relationship between quantum many-body systems and space-time
    geometry. In this study, we demonstrate that these two theories are closely
    related to each other by shedding light on holographic aspects of DMFT,
    particularly for electrons with a semicircle density of states. We formulate a
    holographic renormalization group for the branch Green's function from the
    outer edge to the interior of the Bethe lattice network, and then find that its
    fixed point can be interpreted as a self-consistent solution of Green's
    function in DMFT. By introducing an effective two-dimensional anti-de Sitter
    space, moreover, we clarify that the scaling dimensions for the branch Green's
    function and the boundary correlation functions of electrons at the outer edge
    of the Bethe lattice network are characterized by the fixed-point Green's
    function. We also perform DMFT computations for the Bethe-lattice Hubbard
    model, which illustrate that the scaling dimensions capture the Mott transition
    in the deep interior.

    Other URL： http://arxiv.org/pdf/2509.19704v1

Grant-in-Aid for Scientific Research

  • The Natural Laws of Extreme Universe--A New Paradigm for Spacetime and Matter from Q uantum Information

    Grant-in-Aid for Transformative Research Areas (A)  2025

  • Quantum many-body systems and tensor networks from quantum information perspectives

    Grant-in-Aid for Transformative Research Areas (A)  2025

Contract research

  • Quantum-classical fusion mediated by tensor network

    JST  JST CREST  2024.10

Charge of on-campus class subject

  • 物理学特別演習1B

    2025   Intensive lecture   Graduate school

  • 物理学特別演習2B

    2025   Intensive lecture   Graduate school

  • 物理学特別研究1B

    2025   Intensive lecture   Graduate school

  • 物理学特別研究2B

    2025   Intensive lecture   Graduate school

  • 海外特別研究2

    2025   Intensive lecture   Graduate school

  • 物理学特別演習3B

    2025   Intensive lecture   Graduate school

  • 物理学特別演習4B

    2025   Intensive lecture   Graduate school

  • 物理学特別演習5B

    2025   Intensive lecture   Graduate school

  • 物理学特別研究3B

    2025   Intensive lecture   Graduate school

  • 物理学特別研究4B

    2025   Intensive lecture   Graduate school

  • 物理学特別研究5B

    2025   Intensive lecture   Graduate school

  • 海外特別研究3

    2025   Intensive lecture   Graduate school

  • 物理学卒業演習B

    2025   Weekly class   Undergraduate

  • 物理学卒業研究B

    2025   Intensive lecture   Undergraduate

  • 海外特別研究3

    2025   Intensive lecture   Graduate school

  • 物理学特別演習3A

    2025   Intensive lecture   Graduate school

  • 物理学特別演習4A

    2025   Intensive lecture   Graduate school

  • 物理学特別演習5A

    2025   Intensive lecture   Graduate school

  • 物理学特別研究3A

    2025   Intensive lecture   Graduate school

  • 物理学特別研究4A

    2025   Intensive lecture   Graduate school

  • 物理学特別研究5A

    2025   Intensive lecture   Graduate school

  • 物理学特別演習1A

    2025   Intensive lecture   Graduate school

  • 物理学特別演習2A

    2025   Intensive lecture   Graduate school

  • 物理学特別研究1A

    2025   Intensive lecture   Graduate school

  • 物理学特別研究2A

    2025   Intensive lecture   Graduate school

  • 量子統計力学A

    2025   Weekly class   Graduate school

  • 物理学卒業演習A

    2025   Weekly class   Undergraduate

  • 物理学卒業研究A

    2025   Intensive lecture   Undergraduate

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Charge of off-campus class subject

  • quantum statistical mechanics A

    2025.04
    -
    Now
    Institution：Osaka Metropolitan University

  • 統計力学演習I

    Institution：Niigata University

  • 課題探索特講

    Institution：Niigata University

  • 統計力学III

    Institution：Niigata University

  • 基礎物理学演習I

    Institution：Niigata University

  • 基礎物理学演習II

    Institution：Niigata University

  • 多体問題

    Institution：Niigata University

  • 多体系物理学

    Institution：Niigata University

  • 専門力アクティブラーニング

    Institution：Niigata University

  • 物性物理学I

    Institution：Niigata University

  • 物性物理学II

    Institution：Niigata University

  • 物理学基礎AII

    Institution：Niigata University

  • 物理学基礎ゼミ

    Institution：Niigata University

  • 物理学演習II

    Institution：Niigata University

  • 物理学演習III

    Institution：Niigata University

  • 物理数学演習I

    Institution：Niigata University

  • 現代物理学

    Institution：Niigata University

  • 理学・スタディースキルズ

    Institution：Niigata University

  • 統計力学I

    Institution：Niigata University

  • 統計力学II

    Institution：Niigata University

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Social Activities　⇒ Link to the list of Social Activities

  • Associate Editors

    Role(s)： Edit

    Type： Promotional material

    Physical Society of Japan  J Phys Soc Jpn.  2022.04 - Now

  • 日本物理学会領域１１世話人

    Role(s)： Logistic support

  • 日本物理学会・領域３運営委員

    Role(s)： Logistic support