Hayata, Tomoya

写真a

Affiliation

School of Medicine (Hiyoshi)

Position

Associate Professor (Non-tenured)
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Research Areas 【 Display / hide 】

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

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Papers 【 Display / hide 】

  • Phase transition on superfluid vortices in Higgs-Confinement crossover

    Tomoya Hayata, Yoshimasa Hidaka, Dan Kondo

    Journal of High Energy Physics 2025 ( 3 )  2025.03

    　View Summary

    We propose a novel method to distinguish states of matter by identifying spontaneous symmetry breaking on extended objects, such as vortices, even in the absence of a bulk phase transition. As a specific example, we investigate the phase transition on superfluid vortices in the Higgs-confinement crossover using a U(1)gauge × U(1)global model in (3 + 1) dimensions. This model exhibits superfluidity of U(1)global symmetry and allows for a crossover between the Higgs and confinement regimes by varying the gauge coupling constant from weak to strong. We demonstrate that, on vortices, spontaneous breaking of the ℤ2 flavor symmetry occurs in the weak coupling (Higgs) regime, while it does not in the strong coupling (confinement) regime. We also confirm that those regimes are separated by a second-order phase transition through Monte Carlo simulations, whose universality class corresponds to the two-dimensional Ising model.

  • Floquet evolution of the q -deformed SU(3)1 Yang-Mills theory on a two-leg ladder

    Tomoya Hayata, Yoshimasa Hidaka

    Physical Review D 111 ( 3 )  2025.02

    ISSN  24700010

    　View Summary

    We simulate Floquet time-evolution of a truncated SU(3) lattice Yang-Mills
    theory on a two-leg ladder geometry under open boundary conditions using IBM's
    superconducting 156-qubit device ibm\_fez. To this end, we derive the quantum
    spin representation of the lattice Yang-Mills theory, and compose a quantum
    circuit carefully tailored to hard wares, reducing the use of CZ gates. Since
    it is still challenging to simulate Hamiltonian evolution in present noisy
    quantum processors, we make the step size in the Suzuki-Trotter decomposition
    very large, and simulate thermalization dynamics in Floquet circuit composed of
    the Suzuki-Trotter evolution. We demonstrate that IBM's Heron quantum processor
    can simulate, by error mitigation, Floqeut thermalization dynamics in a large
    system consisting of $62$ qubits. Our work would be a benchmark for further
    quantum simulations of lattice gauge theories using real devices.

  • Floquet evolution of the -deformed Yang-Mills theory on a two-leg ladder

    T Hayata, Y Hidaka

    Physical Review D 111 (3), 034513  2025

  • Floquet prethermalization of Z2 lattice gauge theory on superconducting qubits

    Tomoya Hayata, Kazuhiro Seki, Arata Yamamoto

    Physical Review D 110 ( 11 )  2024.12

    Lead author, Corresponding author, Accepted,  ISSN  24700010

    　View Summary

    Simulating nonequilibirum dynamics of a quantum many-body system is one of
    the promising applications of quantum computing. We simulate the time evolution
    of one-dimensional ${\bf Z}_2$ lattice gauge theory on IBM's superconducting
    156-qubit device ibm\_fez. We consider the Floquet circuit made of the Trotter
    decomposition of Hamiltonian evolution and focus on its dynamics toward
    thermalization. Quantum simulation with the help of error mitigation is
    successful in running the Floquet circuit made of $38$ and $116$ qubits up to
    $10$ Trotter steps in the best case. This is enough to reach the early stage of
    prethermalization. Our work would be a benchmark for the potential power of
    quantum computing for high-energy physics problems.

  • Chiral fermion on quantum computers

    Arata Yamamoto, Tomoya Hayata, Katsumasa Nakayama

    arXiv preprint arXiv:2309.10507 453 2024.11

    ISSN  23318422

    　View Summary

    Quantum computation often suffers from artificial symmetry breaking. We
    should strive to suppress the artifact both by theoretical and technological
    improvements. The theoretical formalism of the lattice fermion with exact
    chiral symmetry is called the chiral fermion. In this presentation, we show how
    the chiral fermion describes chiral physics in quantum computing. We also show
    that, although a drawback of the chiral fermion is large computational cost,
    there is a loophole in one dimension.

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

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Reviews, Commentaries, etc. 【 Display / hide 】

  • Simulating Floquet scrambling circuits on trapped-ion quantum computers

    Kazuhiro Seki, Yuta Kikuchi, Tomoya Hayata, Seiji Yunoki

    arXiv preprint arXiv:2405.07613  2024.05

    ISSN  23318422

    　View Summary

    Complex quantum many-body dynamics spread initially localized quantum
    information across the entire system. Information scrambling refers to such a
    process, whose simulation is one of the promising applications of quantum
    computing. We demonstrate the Hayden-Preskill recovery protocol and the
    interferometric protocol for calculating out-of-time-ordered correlators to
    study the scrambling property of a one-dimensional kicked-Ising model on
    20-qubit trapped-ion quantum processors. The simulated quantum circuits have a
    geometrically local structure that exhibits the ballistic growth of
    entanglement, resulting in the circuit depth being linear in the number of
    qubits for the entire state to be scrambled. We experimentally confirm the
    growth of signals in the Hayden-Preskill recovery protocol and the decay of
    out-of-time-ordered correlators at late times. As an application of the created
    scrambling circuits, we also experimentally demonstrate the calculation of the
    microcanonical expectation values of local operators adopting the idea of
    thermal pure quantum states.

  • Lindblad evolution without the sign problem

    Tomoya Hayata

    arXiv preprint arXiv:2107.07059  2021.07

    ISSN  23318422

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    Quantum Monte Carlo is one of the most powerful numerical tools for studying
    nonpeturbative properties of quantum many-body systems. However, its
    application to real-time problems is limited since the complex and
    highly-oscillating path-integral weight of the real-time evolution harms the
    important sampling. % , which is the notorious sign problem. In this Letter, we
    show that some real-time problems in open fermion systems can be simulated
    using the quantum Monte Carlo. To this end, we prescribe a mapping between a
    real-time problem in open quantum systems and a statistical problem in
    non-Hermitian quantum systems; for some cases, the latter can be solved without
    suffering from the complex measure problem. To explain our idea and demonstrate
    how it works, we compute the real-time evolution of fidelities in open fermion
    systems under dissipation.

  • Chirality-driven edge flow and non-Hermitian topology in active nematic cells

    Lisa Yamauchi, Tomoya Hayata, Masahito Uwamichi, Tomoki Ozawa, Kyogo Kawaguchi

     2020.08

    　View Summary

    Many of the biological phenomena involve collective dynamics driven by
    self-propelled motion and nonequilibrium force (i.e., activity) that result in
    features unexpected from equilibrium physics. On the other hand, biological
    experiments utilizing molecular motors, bacteria, and mammalian cells have
    served as ideal setups to probe the effect of activity in materials and compare
    with theory. As has been established, however, biomolecules are chiral in
    nature, which can lead to the chiral patterning of cells and even to the
    left-right symmetry breaking in our body. The general mechanism of how the
    dynamics of bio-matters can couple with its own inherent chirality to produce
    macroscopic patterns is yet to be elucidated. Here we report that cultured
    neural progenitor cells (NPCs), which undergo self-propelled motion with
    nematic cell-to-cell interactions, exhibit large scale chiral patterns when
    flowing out from containers made by gel. Moreover, a robust chiral cell flow is
    produced along the boundary when the NPCs are cultured on substrates with
    edges. Perturbation by actomyosin inhibitors allowed control over the
    chirality, resulting in the switching of the direction of the chiral patterning
    and boundary flow. As predicted by a hydrodynamic theory analogous to the
    non-Hermitian Schrodinger equation, we find an edge-localized unidirectional
    mode in the Fourier spectrum of the cell density, which corresponds to the
    topological Kelvin wave. These results establish a novel mechanism of flow that
    emerges from a pool of bipolar cells, and demonstrate how topological concepts
    from condensed matter physics can naturally arise in chiral active systems and
    multi-cellular phenomena.

  • Diffusive Nambu-Goldstone modes in quantum time-crystals

    Tomoya Hayata, Yoshimasa Hidaka

     2018.08

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    We study the Nambu-Goldstone (NG) modes associated with spontaneous breaking
    of the continuous time-translation symmetry. To discuss a quantum time-crystal
    with the spontaneously-broken continuous time-translation symmetry, we
    introduce the van der Pol type nonlinear-friction to open quantum systems. By
    considering small fluctuations around a time-periodic mean-field solution, we
    show that a gapless collective mode necessarily appears; this is nothing but
    the NG mode associated with a time crystal. We show that its dispersion
    relation becomes $\omega=-iC\bm p^2$. We also show that noncommutative breaking
    of the time-translation and U(1) symmetries results in mixing of the NG modes,
    and the (typically) propagating NG mode appears, whose dispersion relation
    becomes $\omega=(\pm C_1-iC_2)\bm p^2$.

  • Anomalous transport phenomena from dissipative charge pumping

    Tomoya Hayata

     2017.06

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    The Berry curvature involving time and momentum derivatives, which we term
    emergent electric field, induces a nondisspative current known as the adiabatic
    charge pumping or Thouless pumping in periodically driven systems. We study
    dissipative currents originated from the interplay between emergent electric
    fields and electric/magnetic fields in two and three dimensions on the basis of
    the Boltzmann transport theory. As an example of two-dimensional models, we
    study the Rashba Hamiltonian with time-dependent and anisotropic spin-orbit
    coupling. We show that the interplay between emergent electric fields and
    electric fields leads to a current transverse to electric fields, which is
    symmetric and contributes to the entropy production. As an example of
    three-dimensional models, we study the Weyl Hamiltonian under AC electric
    fields. We show that the interplay between emergent electric fields and
    magnetic fields leads to a Hall-type current at zero DC electric fields, which
    is now transverse to DC magnetic fields: $j_{x}=\sigma_{xy}B_y$
    ($\sigma_{xy}=-\sigma_{yx}$). The Hall photocurrent is relevant in the
    inversion symmetry breaking Weyl semimetals such as TaAs or SrSi$_2$.

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

  • ゲージ理論のための量子計算手法の開発と非平衡現象への応用

    2024.04
    -
    2027.03

    日本学術振興会, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Principal investigator

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    近年の量子計算機や量子情報理論の急速的な進展によって、量子計算もしくは関連する計算手法（特にテンソルネットワークに基づく手法）を素粒子・原子核物理学、すなわち、場の量子論的な系の問題へと応用する試みが注目を集めている。本研究は場の量子論の中でも特に宇宙初期や高エネルギー重イオン衝突実験の物理で重要になるゲージ理論の時間発展を計算するための量子計算手法の開発を行う。簡単な非平衡問題に関して開発した計算手法を超伝導型量子計算機を使って実際に実行することで、手法の開発に留まらず、より将来的な応用へと繋がる実践的な研究を行うことを目標とする。

  • Chiral transport phenomena in active matters

    2021.04
    -
    2024.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, HAYATA Tomoya, Grant-in-Aid for Scientific Research (B), Principal investigator

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    We experimentally found a chirality-driven collective motion in active matters, and revealed the microscopic mechanism based on a agent-based model. Through quantitative comparison between experiments and numerical simulations based on a agent-based model, we construct a method to determine parameters of a agent-based model from experimental observables and make a theoretical prediction based on the agent-based model obtained from experiments.

  • Study of Nonequilibrium and high-density QCD using Hamiltonian formalism

    2021.04
    -
    2024.03

    Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), No Setting

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    極限状態におけるハドロン多体系の物理における２つの未解決問題: ハドロンの非平衡ダイナミクス及び，高密度ハドロン物質の相構造の理解の問題の定性的理解を目指す．これらの状態の理解は宇宙初期の時間発展，高エネルギー重イオン衝突の物理や中性子星の内部がどのような状態になりどのような状態方程式が実現されるかを理解する上で重要になる．格子上のハミルトニアン形式を用いて，その実時間発展や高密度状態を数値シミュレーションすることで，どのようにハドロンが熱平衡状態にいたるか，高密度ハドロンの相構造はどのようになるか明らかにする．
    (1+1)次元系のQCDの有限密度の問題に取り組んだ． (1+1)次元系では，グルーオンのダイナミカルな自由度が存在しない．そのため，適切なユニタリ変換を施すことで，フェルミオンのみの自由度で書かれたハミルトニアンに変換することができる．また，フェルミオンをスピン系に変換する手法を用いることで，問題は，(1+1)次元のスピン系の問題に帰着することができる．さらに，(1+1)次元系では，密度演算子のくりこみ群の手法が有効である．我々は，SU(2)及びSU(3)の(1+1)次元QCDをスピン系に変換し，開放端境界条件のもと，密度演算子くりこみ群を用いて解析した．我々は，状態方程式や，密度分布，カイラル凝縮や分布関数の振る舞いを調べることで，有限密度QCDの振る舞いを考察することができた．まず，開放端境界条件の有限密度では，SU(2)，SU(3)ともに非一様相が実現することがわかった．また，SU(2)QCDでは，分布関数の振る舞いが，BEC/BCSクロスオーバーと類似した振る舞いを示していることがわかった．ここで，BECはボーズアインシュタイン凝縮，BCSはバーディーン-クーパー-シュリーファーの頭文字を表す．興味深いことに，SU(3)QCDに関しても同様の分布関数の振る舞いが確認された．
    高次元への拡張として，ハニカム格子上の(2+1)次元SU(2)ゲージ理論の定式化に取り組んだ．定式化は完了し，小さい自由度の場合には，厳密対角化を用いた数値計算もうまくいくことがわかった．
    (1+1)次元のQCDの性質を調べる研究がうまくいっているため．また，SU(3)におけるガウスの拘束条件を解いて，具体的なヒルベルト空間を構成する方法も出来上がりつつある．
    まず，(1+1)次元QCDの研究成果を論文にまとめる．並行して，高次元への拡張の研究及び，（１＋１）次元QCDの実時間発展の問題に取り組む．

  • 複素ランジュバン法を用いた非平衡量子系の研究

    2016.04
    -
    2019.03

    日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, No Setting

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    本年度は、非平衡量子開放系における自発的対称性の破れ、特に、南部-ゴールドストーンモードの研究を行った。南部-ゴールドストーンモードは自発的対称性の破れに伴い普遍的に現れるギャップレスモードであり、対称性の自発的に破れた系の低エネルギーダイナミクスを決定する。本研究では、時間的に振動する凝縮を伴う非平衡定常状態について、その低エネルギーダイナミクスを南部-ゴールドストーンモードを通じて解析した。
    近年、時間結晶と呼ばれる時間並進対称性が自発的に破れた量子物質の存在が理論的に提案され、いくつかの系においてその実験的な検証がなされている。南部-ゴールドストーンモードは連続的な対称性が自発的に破れれば一般的に現れるため、時間結晶においても南部-ゴールドストーンモードが現れると期待される。我々はヴァンデルポール振動子と呼ばれる力学系を場の理論的な系に一般化し、非平衡定常状態における時間周期解とその周りの摂動を調べた。その結果、時間並進対称性が自発的に破れた解の周りでは時間並進対称性を復元する力学的自由度に結合するゼロモード、つまり、時間並進対称性の自発的破れに伴う南部-ゴールドストーンモードが必ず現れることを発見した。さらに、時間並進対称性と内部[U(1)]対称性が非可換的に破れる系を理論的に構成することで、保存系では現れないタイプの（過減衰を起こした）南部-ゴールドストーンモードが時間結晶では現れることを示した。

  • 正準交換関係に基づく新しいＱＣＤ和則の構築と、そのＱＣＤ物性への応用

    2012.04
    -
    2015.03

    日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, No Setting

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    本年度は、媒質中のQCD和則ついての研究を行った。昨年度までの研究をより一般の場合、特に有限温度、有限密度の場合に拡張し、その拡張した和則の現象論的応用を行った。これまでに得られた成果を論文にまとめているところであり、今後、論文を投稿する予定である。
    また、交付申請書に記載されていない研究をいくつか行い、成果を論文にまとめて発表した。南部-ゴールドストーンボソンの一般論についての研究を行い、論文を2件投稿した。これらについてはすでに出版されている。一つ目の論文では、有限温度、有限密度中での、南部-ゴールドストーンボソンの分散の計算、特に分散の虚部の振る舞いを解析し、有限温度媒質中での南部-ゴールドストーンボソンの長波長での振る舞いを一般的に議論した。もう一つの論文では、時空対称性を含むより一般の場合についての弾性変数の数勘定の定理を議論した。また、強い電場中でのシュウィンガー効果についての論文を1件投稿した。これもすでに出版されている。確率過程量子化に基づくシュウィンガー効果の解析方法を構成し、簡単な例を用いて構成した方法が実際にうまく使えることを実演した。今後、構成した方法を用いて、重イオン衝突や物性実験を解析する研究を行う予定である。
    他にも、非一様な閉じこめ相転移や、複素ランジュバン法を用いた量子渦の生成の第一原理的計算、さらに、相対論的流体力学の場の量子論からの導出に関する研究など3件を論文として投稿した。
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Courses Taught 【 Display / hide 】

  • PHYSICS 2

    2025

  • PHYSICS 1

    2025

  • LABORATORY OF PHYSICS

    2025

  • LABORATORY OF PHYSICS

    2024

  • PHYSICS 1

    2024

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