KEIO RESEARCHERS INFORMATION SYSTEM

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

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

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Phases of the $q$-deformed $\mathrm{SU}(N)$ Yang-Mills theory at large $N$

  Tomoya Hayata, Yoshimasa Hidaka, Hiromasa Watanabe

   2026.01

  　View Summary

  We investigate the $(2+1)$-dimensional $q$-deformed $\mathrm{SU}(N)_k$ Yang-Mills theory in the lattice Hamiltonian formalism, which is characterized by three parameters: the number of colors $N$, the coupling constant $g$, and the level $k$. By treating these as tunable parameters, we explore how key properties of the theory, such as confinement and topological order, emerge in different regimes. Employing a variational mean-field analysis that interpolates between the strong- and weak-coupling regimes, we determine the large-$N$ phase structure in terms of the 't Hooft coupling $λ_\mathrm{tH}=g^2N$ and the ratio $k/N$. We find that the topologically ordered phase remains robust at large $N$ under appropriate scalings of these parameters. This result indicates that the continuum limit of large-$N$ gauge theory may be more intricate than naively expected, and motivates studies beyond the mean-field theory, both to achieve a further understanding of confinement in gauge theories and to guide quantum simulations of large-$N$ gauge theories.

• Quantum anomaly for benchmarking quantum computing

  T Hayata, A Yamamoto

  arXiv preprint arXiv:2603.03697  2026

  　View Summary

  Given the rapid advances in quantum computing hardware, establishing systematic strategies for verifying the correctness of quantum computations has become increasingly important. Exploiting the fact that the axial anomaly in gauge theories is exact to all orders in perturbation theory, we propose the axial anomaly as a nontrivial benchmark for quantum simulations of lattice gauge theories. We simulate anomalous axial-charge production in ${\mathbb Z}_N$ lattice gauge theories on the trapped-ion quantum computer ``Reimei''. After taking the U(1), infinitesimal time, and infinite volume limits, we successfully reproduce the anomaly coefficient within statistical uncertainties, even without error mitigation. Our results demonstrate that the axial anomaly can be simulated on current quantum computers and serves as a verification test of quantum computations.

• Phases of the -deformed Yang-Mills theory at large

  T Hayata, Y Hidaka, H Watanabe

  arXiv preprint arXiv:2601.03843  2026

• Onset of thermalization of q-deformed SU (2) Yang-Mills theory on a trapped-ion quantum computer

  T Hayata, Y Hidaka, Y Kikuchi

  arXiv preprint arXiv:2601.13530  2026

  　View Summary

  Nonequilibrium dynamics of quantum many-body systems is one of the main targets of quantum simulations. This focus - together with rapid advances in quantum-computing hardware - has driven increasing applications in high-energy physics, particularly in lattice gauge theories. However, most existing experimental demonstrations remain restricted to (1+1)-dimensional and/or abelian gauge theories, such as the Schwinger model and the toric code. It is essential to develop quantum simulations of nonabelian gauge theories in higher dimensions, addressing realistic problems in high-energy physics. To fill the gap, we demonstrate a quantum simulation of thermalization dynamics in a (2+1)-dimensional $q$-deformed $\mathrm{SU}(2)_3$ Yang-Mills theory using a trapped-ion quantum computer. By restricting the irreducible representations of the gauge fields to the integer-spin sector of $\mathrm{SU}(2)_3$, we obtain a simplified yet nontrivial model described by Fibonacci anyons, which preserves the essential nonabelian fusion structure of the gauge fields. We successfully simulate the real-time dynamics of this model using quantum circuits that explicitly implement $F$-moves. In our demonstrations, the quantum circuits execute up to 47 sequential $F$-moves. We identify idling errors as the dominant error source, which can be effectively mitigated using dynamical decoupling combined with a parallelized implementation of $F$-moves.

• Dissipative ground-state preparation of a quantum spin chain on a trapped-ion quantum computer

  K Seki, Y Kikuchi, T Hayata, S Yunoki

  arXiv preprint arXiv:2601.08137  2026

  　View Summary

  We demonstrate a dissipative protocol for ground-state preparation of a quantum spin chain on a trapped-ion quantum computer. As a first step, we derive a Kraus representation of a dissipation channel for the protocol recently proposed by Ding et al. [Phys. Rev. Res. 6, 033147 (2024)] that still holds for arbitrary temporal discretization steps, extending the analysis beyond the Lindblad dynamics regime. The protocol guarantees that the fidelity with the ground state monotonically increases (or remains unchanged) under repeated applications of the channel to an arbitrary initial state, provided that the ground state is the unique steady state of the dissipation channel. Using this framework, we implement dissipative ground-state preparation of a transverse-field Ising chain for up to 19 spins on the trapped-ion quantum computer Reimei provided by Quantinuum. Despite the presence of hardware noise, the dynamics consistently converges to a low-energy state far away from the maximally mixed state even when the corresponding quantum circuits contain as many as 4110 entangling gates, demonstrating the intrinsic robustness of the protocol. By applying zero-noise extrapolation, the resulting energy expectation values are systematically improved to agree with noiseless simulations within statistical uncertainties.

display all >>

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

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

• Chiral transport phenomena in active matters

  Hayata, Tomoya

  科学研究費補助金研究成果報告書 2023

• Real-time dynamics of topological phenomena in active nematics

  Hayata, Tomoya

  学事振興資金研究成果実績報告書 (慶應義塾大学)  2020

Reviews, Commentaries, etc. 【 Display / hide 】

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.

  • Access to Document (DOI)

• Dense QCD₂ with matrix product states

  Hayata, T. and Hidaka, Y. and Nishimura, K.

  Journal of High Energy Physics 2024 ( 7 )  2024

  ISSN  10298479

  • Access to Document (DOI)

• q deformed formulation of Hamiltonian SU(3) Yang-Mills theory

  早田智也, 日高義将

  日本物理学会講演概要集(CD-ROM) 79 ( 1 )  2024

  ISSN  2189-079X

• Quantum many-body scars in lattice gauge theories

  早田智也, 日高義将, 西村健太郎

  日本物理学会講演概要集(CD-ROM) 78 ( 1 )  2023

  ISSN  2189-079X

• q deformed formulation of Hamiltonian SU(3) Yang-Mills theory

  Hayata, T. and Hidaka, Y.

  Journal of High Energy Physics 2023 ( 9 )  2023

  ISSN  10298479

  • Access to Document (DOI)

display all >>

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

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

• Exploring the QCD Phase Diagram through Generalized Symmetries

  2025.04

  -

  2029.03

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

  　View Summary

  QCD相構造，特に高密度QCD相の理解は大きな未解決問題でありその解明は，ハドロン物理の大きな目標のひとつである．
  理論的には非摂動的解析に困難があり，高密度QCD相の理解を進展させるには既存の解析手法及び発想とは異なるアプローチが不可欠である．
  近年進展が著しい一般化対称性は非摂動的アプローチとして有力視されている方法であり，一般化対称性を用いて高密度QCDの問題に挑む．
  特に，位相欠陥のような広がった物体に注目し，その上の新奇な相転移や，輸送現象の解明を通じて高密度QCD相の相構造の解明に挑む．

• 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

  　View Summary

  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

  　View Summary

  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, Hidaka Yoshimasa, Grant-in-Aid for Scientific Research (B), No Setting

  　View Summary

  To overcome the limitations of conventional Monte Carlo methods in tracing how protons and neutrons emerged from the quark-gluon plasma of the early universe and in probing the interiors of high dense Matter such as neutron stars, we developed a new Hamiltonian-based framework and achieved the following results: Real-time simulations on small lattices revealed that thermalization occurs within the short Boltzmann time scale. By reformulating gauge theories with quantum groups, we validated the method's reliability through direct comparison with Monte Carlo data. Applying the density matrix renormalization group to (1+1)-dimensional finite-density systems, we determined the equation of state.

• 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

  　View Summary

  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。

display all >>

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• PHYSICS 2

  2025

• PHYSICS 1

  2025

• LABORATORY OF PHYSICS

  2025

• PHYSICS 2

  2024

• PHYSICS 1

  2024

display all >>