Morita, Satoshi

写真a

Affiliation

Graduate School of Science and Technology ( Yagami )

Position

Project Associate Professor (Non-tenured)
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Papers 【 Display / hide 】

  • Tensor Renormalization Group Calculations of Partition-Function Ratios

    Satoshi Morita, Naoki Kawashima

    Journal of the Physical Society of Japan 95 ( 4 )  2026.04

    ISSN  00319015

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    The behavior of dimensionless quantities defined as ratios of partition functions is analyzed to investigate phase transitions and critical phenomena. At criticality, the universal values of these ratios can be predicted from conformal field theory (CFT) through the modular-invariant partition functions on a torus. We perform numerical calculations using the bond-weighted tensor renormalization group for three two-dimensional models belonging to different universality classes: the Ising model, the three-state Potts model, and the four-state Potts model. The partition-function ratios obey the same finite-size scaling form as the Binder parameter, and their critical values agree well with the universal values predicted by CFT. In the four-state Potts model, we observe logarithmic corrections in the system-size dependence of these ratios.

  • TeNeS-v2: Enhancement for real-time and finite temperature simulations of quantum many-body systems

    Yuichi Motoyama, Tsuyoshi Okubo, Kazuyoshi Yoshimi, Satoshi Morita, Tatsumi Aoyama, Takeo Kato, Naoki Kawashima

    Computer Physics Communications 315 2025.10

    ISSN  00104655

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    Quantum many-body systems are challenging targets for computational physics due to their large number of degrees of freedom. The tensor networks, particularly Tensor Product States (TPS) and Projected Entangled Pair States (PEPS), effectively represent these systems on two-dimensional lattices. However, the technical complexity of TPS/PEPS-based coding can be challenging for many researchers to manage effectively. To reduce this problem, we developed TeNeS (Tensor Network Solver). This paper introduces TeNeS-v2, which extends TeNeS with real-time and finite temperature simulations, providing deeper insights into quantum many-body systems. We detail the new algorithms, input/output design, and application examples, demonstrating TeNeS-v2's applicability to various quantum spin and Bose models on two-dimensional lattices. New version program summary: Program Title: TeNeS CPC Library link to program files: https://doi.org/10.17632/psm26xxbvd.2 Developer's repository link: https://github.com/issp-center-dev/TeNeS Licensing provisions: GPLv3 Programming language: C++11 Journal reference of previous version: Comput. Phys. Commun. (2022) 279, 108437, doi:10.1016/j.cpc.2022.108437 Reasons for the new version: To extend the capabilities of TeNeS to include real-time and finite temperature simulations, enabling deeper insights into quantum many-body systems beyond ground states. Summary of revisions: TeNeS-v2 introduces real-time evolution and finite temperature simulation capabilities, expanding the range of quantum many-body phenomena that can be studied. Nature of problem: Quantum many-body systems are extremely difficult to simulate because of the huge dimension of the Hilbert space. Conventional methods have difficulty in accurately representing these systems, especially for properties beyond small lattices and ground states. Advanced computational techniques are required to efficiently capture the dynamics and thermal properties of these systems. Solution method: TeNeS employs tensor networks, specifically Tensor Product States (TPS) and Projected Entangled Pair States (PEPS), to efficiently represent quantum many-body states on two-dimensional lattices. The real-time evolution is handled through a straightforward extension of imaginary time evolution methods, allowing the study of dynamical properties. Finite temperature simulations are conducted using an imaginary time evolution approach starting from the infinite-temperature mixed state. These methods enable the accurate calculation of various physical properties in different quantum states. Additional comments including restrictions and unusual features: TeNeS-v2 maintains ease of use by providing flexible input file configurations and supporting a variety of two-dimensional lattice models. Increasing the bond dimension to improve accuracy requires more computational resources. Finite temperature calculations may exhibit unphysical behavior due to limitations of the tensor network approximation method. Users should be aware of these potential problems and interpret the results following the suggestions made in the text.

  • Tensor network renormalization approach to antiferromagnetic 6-state clock model on the Union Jack lattice

    Kenji Homma, Satoshi Morita, Naoki Kawashima

    Physical Review B 111 ( 13 )  2025.04

    ISSN  24699950

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    Using the nuclear norm regularization techniques on tensor network renormalization algorithm, we study the phase diagram, the critical behavior, and the duality property of the antiferromagnetic 6-state clock model on the Union Jack lattice. We find that this model undergoes multiple phase transitions; there is the Berezinskii-Kosterlitz-Thouless, Z6 symmetry breaking, and chiral transition with decreasing temperature. Furthermore, we provide convincing numerical evidence that its quasi-long-range order is well explained by the compactified boson conformal field theory (CFT) and the chiral transition is in perfect agreement with the Ising CFT, including central charge, scaling dimension spectrum, and operator product expansion coefficients.

  • Multi-impurity method for the bond-weighted tensor renormalization group

    Satoshi Morita, Naoki Kawashima

    Physical Review B 111 ( 5 )  2025.02

    ISSN  24699950

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    We propose a multi-impurity method for the bond-weighted tensor renormalization group (BWTRG) to compute the higher-order moment of physical quantities in a two-dimensional system. The replacement of the bond weight with an impurity matrix in a bond-weighted triad tensor network represents a physical quantity such as the magnetization and the energy. We demonstrate that the accuracy of the proposed method is much higher than the conventional tensor renormalization group for the Ising model and the five-state Potts model. Furthermore, we perform the finite-size scaling analysis and observe that the dimensionless quantity characterizing the structure of the fixed point tensor satisfies the same scaling relation in the critical region as the Binder parameter. The estimated critical temperature dependence on the bond dimension indicates that the exponent relating the correlation length to the bond dimension varies continuously with respect to the BWTRG hyperparameter. We find that BWTRG with the optimal hyperparameter is more efficient in terms of computational time than alternative approaches based on the matrix product state in estimating the critical temperature.

  • Optimization of conveyance of quantum particles by moving potential well

    Satoshi Morita, Yoshiaki Teranishi, Seiji Miyashita

    Physical Review Research 6 ( 4 )  2024.10

    ISSN  26431564

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    Quantum mechanical control of the position of a particle by using a trapping potential well is an important problem for the manipulation of a quantum particle. We study the probability of successful conveyance of the particle trapped in a potential well for a given length within a given fixed time, i.e., survival probability after the motion. For the actual motion of conveyance, we need to accelerate the particle to move and then decelerate it to stop at the destination. Acceleration and deceleration cause a dropoff of a particle from the trapping potential well. The relaxation of the survival probability in a process with a constant acceleration rate is studied in detail. First, the process is studied as the relaxation of the survival probability of the trapped particle by direct numerical calculations. The survival probability obeys an exponential decay in a long time, which is analyzed from a viewpoint of eigenvalue problem. The value of survival probability is also estimated by the Wentzel-Kramers-Brillouin method with connection formulas using the Airy function and the Weber function. The value is further estimated by a method of the resonance states. We emphasize the fact that an important source of dropoff comes from a nonanalytic change of velocity at the starting point. When the rested particle begins to move, the ground state of the rest frame is redistributed to eigenstates of the moving frame, and then each eigenstate of the moving frame evolves in time. The dephasing of wave functions of the distributed populations reduces the probability of successful conveyance. In general, a smooth start gives a small initial disturbance but it requires a large acceleration during the process to reach the destination in the fixed time which causes a larger dropoff in the process. Considering these conflicting facts, we study the survival probability in concrete conveyance schemes, i.e., protocols with (1) a sudden change of velocity to a constant velocity, (2) a sudden change of acceleration rate to a constant acceleration, and (3) a smooth change of acceleration by studying the real-time change of populations of the adiabatic (instantaneous) eigenstates. We observe the time evolution of the trapped probability and the population distribution during the conveyance process. In cases that the potential well has several bound states, we propose a method to select the particle trapped at the ground state by making use of the difference of survival probabilities of bound states.

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Reviews, Commentaries, etc. 【 Display / hide 】

  • テンソルネットワークと統計力学

    森田 悟史

    数理科学 60 ( 2 ) 15 - 22 2022.02

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Presentations 【 Display / hide 】

  • Analysis of Phase Transitions and Critical Phenomena using Bond-Weighted Tensor Renormalization Group

    Satoshi Morita, Naoki Kawashima

    [International presentation]  Tensor Network States: Algorithms and Applications 2025 (TNSAA 2025) (National Cheng Kung University, Tainan) , 

    2025.12
    , 

    Oral presentation (invited, special)

  • Multi-impurity method for bond-weighted tensor renormalization group

    Satoshi Morita, Naoki Kawashima

    [International presentation]  Tensor Network States: Algorithms and Applications 2024 (TNSAA 2024) (Henry Cheng International Conference Centre, Hong Kong) , 

    2024.12
    , 

    Poster presentation

  • テンソルくりこみ群による相転移・臨界現象の解析

    森田 悟史

    Tensor Network 2024 in Kanazawa (石川県政記念 しいのき迎賓館) , 

    2024.11
    , 

    Oral presentation (invited, special)

  • Multi-impurity method for bond weighted tensor renormalization group

    Satoshi Morita, Naoki Kawashima

    [International presentation]  28th International Conference on Statistical Physics (STATPHYS28) (The University of Tokyo, Hongo campus, Tokyo) , 

    2023.08
    , 

    Oral presentation (general)

  • Multi-impurity method for bond weighted tensor renormalization group

    Satoshi Morita, Naoki Kawashima

    [International presentation]  Conference on Computational Physics (CCP2023) (Kobe International Conference Center) , 

    2023.08
    , 

    Oral presentation (general)

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

  • Improvement of tensor network renormalization group and high accuracy analysis of phase transitions and critical phenomena

    2020.04
    -
    2024.03

    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Principal investigator

    　View Summary

    今年度は、(1) 複数の引力相互作用が存在する古典ダイマー模型の研究、 (2) 1次元量子スピン梯子模型における研究、(3) 離散的なスピン回転対称性を持つ古典スピン系におけるビンダー比の振る舞いの研究を主に行った。
    (1)に関しては、行列積状態を用いた数値計算を行い相転移の普遍性を特定した．特に，コラムナー秩序相から無秩序相への転移は、臨界指数が連続的に変化するAshkin-Teller模型と同じ普遍性を持つことを明らかにした．これにより、幅広いパラメータ領域で、Ashkin-Teller型相転移を起こす臨界面が存在することが判明した。また、並進対称を破らずに配向秩序をもつネマティック状態が存在する場合は、高温側に回転対称性を破る相転移、低温側に並進対称性を破る相転移が存在する。どちらの相転移も、2次元イジング模型と同じ普遍性に属することを明らかにした。
    (2)に関しては、行列積状態を用いた数値計算と有効的な場の理論を用いた解析を組み合わせ、異方的相互作用が存在する1次元量子スピン梯子における量子相転移の研究を行った。前年度からの進展としては、対称性によって守られたトポロジカルな相が存在するパラメータ領域を含む領域を考察し、トポロジカルな指数を用いて相を明確に同定した。また、次々近接相互作用を含むスピン1の量子スピン梯子模型において、直積状態が基底状態となり、異なる系列の磁気プラトーが磁化曲線に現れるパラメータ領域を求めることに成功した。

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Awards 【 Display / hide 】

  • HPCIソフトウェア賞（開発部門賞）最優秀賞

    mVMC開発者チーム, 2023.05, 一般社団法人HPCIコンソーシアム, mVMC

  • Outstanding Paper Award of the Physical Society of Japan

    Ryui Kaneko, Satoshi Morita, Masatoshi Imada, 2023.01, The Physical Society of Japan, Gapless Spin-Liquid Phase in an Extended Spin 1/2 Triangular Heisenberg Model

  • Young Scientist Award at the 3rd CMSI meeting

    2012.12, Computational Materials Science Initiative (CMSI), Optimization of many-variable variational Monte Carlo method

    Type of Award： Award from Japanese society, conference, symposium, etc.

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Committee Experiences 【 Display / hide 】

  • 2026.04
    -
    2027.03

    計算物理領域運営委員, 日本物理学会

  • 2019.04
    -
    2020.03

    領域11運営委員, 日本物理学会

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