論文 - 早田　智也

Simulating Floquet scrambling circuits on trapped-ion quantum computers

Kazuhiro Seki, Yuta Kikuchi, Tomoya Hayata, Seiji Yunoki

Physical Review Research 2025年04月

査読有り

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Simulating Floquet scrambling circuits on trapped-ion quantum computers

Seki K., Kikuchi Y., Hayata T., Yunoki S.

Physical Review Research 7 （ 2 ）  2025年04月

ISSN  26431564

　概要を見る

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. Our experiments are made possible by extensively utilizing one of the highest-fidelity quantum processors currently available and, thus, should be considered as a benchmark for the current status of the most advanced quantum computers.

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Phase transition on superfluid vortices in Higgs-Confinement crossover

Hayata T., Hidaka Y., Kondo D.

Journal of High Energy Physics 2025 （ 3 ）  2025年03月

査読有り

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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.

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

Hayata T., Hidaka Y.

Physical Review D 111 （ 3 ）  2025年02月

査読有り,  ISSN  24700010

　概要を見る

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 hardware, reducing the number of controlled-Z 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, Floquet 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.

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Digital quantum simulation of many-body localization crossover in a disordered kicked Ising model

T Hayata, K Seki, S Yunoki

arXiv preprint arXiv:2510.01983 2025年

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

T Hayata, Y Hidaka

Physical Review D 111 (3), 034513 2025年

Simulating Floquet scrambling circuits on trapped-ion quantum computers

K Seki, Y Kikuchi, T Hayata, S Yunoki

Physical Review Research 7 (2), 023032 2025年

Floquet prethermalization of Z2 lattice gauge theory on superconducting qubits

Hayata T., Seki K., Yamamoto A.

Physical Review D 110 （ 11 ）  2024年12月

筆頭著者, 責任著者, 査読有り,  ISSN  24700010

　概要を見る

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 Z2 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.

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Chiral fermion on quantum computers

Yamamoto A., Hayata T., Nakayama K.

Proceedings of Science 453 2024年11月

ISSN  23318422

　概要を見る

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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Dense QCD<inf>2</inf> with matrix product states

Hayata T., Hidaka Y., Nishimura K.

Journal of High Energy Physics （Springer Science and Business Media LLC）  2024 （ 7 ）  2024年07月

査読有り,  ISSN  10298479

　概要を見る

We study one-flavor SU(2) and SU(3) lattice QCD in (1 + 1) dimensions at zero temperature and finite density using matrix product states and the density matrix renormalization group. We compute physical observables such as the equation of state, chiral condensate, and quark distribution function as functions of the baryon number density. As a physical implication, we discuss the inhomogeneous phase at nonzero baryon density, where the chiral condensate is inhomogeneous, and baryons form a crystal. We also discuss how the dynamical degrees of freedom change from hadrons to quarks through the formation of quark Fermi seas.

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Non-Hermitian p -wave superfluid and effects of the inelastic three-body loss in a one-dimensional spin-polarized Fermi gas

Tajima H., Sekino Y., Inotani D., Dohi A., Nagataki S., Hayata T.

Physical Review Research 6 （ 2 ）  2024年04月

査読有り,  ISSN  26431564

　概要を見る

We theoretically investigate non-Hermitian p-wave Fermi superfluidity in one-dimensional spin-polarized Fermi gases which is relevant to recent ultracold atomic experiments. Considering an imaginary atom-dimer coupling responsible for the three-body recombination process in the Lindblad formalism, we discuss the stability of the superfluid state against the atomic loss effect. Within the two-channel non-Hermitian BCS-Eagles-Leggett theory, the atomic loss is characterized by the product of the imaginary atom-dimer coupling and the p-wave effective range. Our results indicate that for a given imaginary atom-dimer coupling, a smaller magnitude of the effective ranges of p-wave interaction is crucial for reaching the non-Hermitian p-wave Fermi superfluid state. Moreover, our theoretical framework for many-body systems with the three-body loss, which is inevitable in ultracold atoms, would promote further progress in non-Hermitian cold-atomic physics.

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Two-dimensional lattice with an imaginary magnetic field

Ozawa T., Hayata T.

Physical Review B （American Physical Society (APS)）  109 （ 8 ）  2024年02月

査読有り,  ISSN  24699950

　概要を見る

We introduce a two-dimensional non-Hermitian lattice model with an imaginary magnetic field and elucidate various unique features which are absent in Hermitian lattice models with real magnetic fields. To describe the imaginary magnetic field, we consider both the Landau gauge and the symmetric gauge, which are related by a generalized gauge transformation, changing not only the phase but also the amplitude of the wave function. We discuss the complex energy spectrum and the non-Hermitian Aharonov-Bohm effect as examples of properties which are due to the imaginary magnetic field independent of the generalized gauge transformation. We show that the energy spectrum does not converge as the lattice size is made larger, which comes from the intrinsic nonperiodicity of the model. However, we have found that the energy spectrum does converge if one fixes the length of one side and makes the other side longer; this asymptotic behavior can be understood in the framework of the non-Bloch band theory. We also find an analog of the Aharonov-Bohm effect; the net change of the norm of the wave function upon adiabatically forming a closed path is determined by the imaginary magnetic flux enclosed by the path, which provides an experimentally observable feature of the imaginary magnetic field.

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Dynamical chirality production in one dimension

Hayata T., Nakayama K., Yamamoto A.

Physical Review D 109 （ 3 ）  2024年02月

査読有り,  ISSN  24700010

　概要を見る

We discuss the quantum computation of dynamical chirality production in lattice gauge theory. Although the chirality of a lattice fermion is complicated in general dimensions, it can be simply formulated on a one-dimensional lattice. The chiral fermion formalism enables us to extract the physical part of the chirality production that would be interpreted as the chiral anomaly in the continuous theory. We demonstrate the computation of the Z2 lattice gauge theory on a classical emulator.

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Non-Hermitian -wave superfluid and effects of the inelastic three-body loss in a one-dimensional spin-polarized Fermi gas

H Tajima, Y Sekino, D Inotani, A Dohi, S Nagataki, T Hayata

Physical Review Research 6 (2), 023060 2024年

Floquet prethermalization of Z₂ lattice gauge theory on superconducting qubits

Hayata, T. and Seki, K. and Yamamoto, A.

arXiv 2024年

ISSN  23318422

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Floquet prethermalization of lattice gauge theory on superconducting qubits

T Hayata, K Seki, A Yamamoto

Physical Review D 110 (11), 114503 2024年

Simulating Floquet scrambling circuits on trapped-ion quantum computers

Seki, K. and Kikuchi, Y. and Hayata, T. and Yunoki, S.

arXiv 2024年

ISSN  23318422

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Dense $\textrm{QCD}_2$ with matrix product states

Tomoya Hayata, Yoshimasa Hidaka, Kentaro Nishimura

2023年11月

　概要を見る

We study one-flavor $\mathrm{SU}(2)$ and $\mathrm{SU}(3)$ lattice QCD in
($1+1$) dimensions at zero temperature and finite density using matrix product
states and the density matrix renormalization group. We compute physical
observables such as the equation of state, chiral condensate, and quark
distribution function as functions of the baryon number density. As a physical
implication, we discuss the inhomogeneous phase at nonzero baryon density,
where the chiral condensate is inhomogeneous, and baryons form a crystal. We
also discuss how the dynamical degrees of freedom change from hadrons to quarks
through the formation of quark Fermi seas.


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

Hayata T., Hidaka Y.

Journal of High Energy Physics 2023 （ 9 ）  2023年09月

査読有り,  ISSN  1029-8479

　概要を見る

We study SU(3) Yang-Mills theory in (2 + 1) dimensions based on networks of Wilson lines. With the help of the q deformation, networks respect the (discretized) SU(3) gauge symmetry as a quantum group, i.e., SU(3) k, and may enable implementations of SU(3) Yang-Mills theory in quantum and classical algorithms by referring to those of the stringnet model. As a demonstration, we perform a mean-field computation of the groundstate of SU(3) k Yang-Mills theory, which is in good agreement with the conventional Monte Carlo simulation by taking sufficiently large k. The variational ansatz of the mean-field computation can be represented by the tensor networks called infinite projected entangled pair states. The success of the mean-field computation indicates that the essential features of Yang-Mills theory are well described by tensor networks, so that they may be useful in numerical simulations of Yang-Mills theory.

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String-net formulation of Hamiltonian lattice Yang-Mills theories and quantum many-body scars in a nonabelian gauge theory

Hayata T., Hidaka Y.

Journal of High Energy Physics 2023 （ 9 ）  2023年09月

査読有り,  ISSN  1029-8479

　概要を見る

We study the Hamiltonian lattice Yang-Mills theory based on spin networks that provide a useful basis to represent the physical states satisfying the Gauss law constraints. We focus on SU(2) Yang-Mills theory in (2 + 1) dimensions. Following the string-net model, we introduce a regularization of the Kogut-Susskind Hamiltonian of lattice Yang-Mills theory based on the q deformation, which respects the (discretized) SU(2) gauge symmetry as quantum group, i.e., SU(2)k, and enables implementation of the lattice Yang-Mills theory both in classical and quantum algorithms by referring to those of the string-net model. Using the regularized Hamiltonian, we study quantum scars in a nonabelian gauge theory. Quantum scars are nonthermal energy eigenstates arising in the constrained quantum many-body systems. We find that quantum scars from zero modes, which have been found in abelian gauge theories arise even in a nonabelian gauge theory. We also show the spectrum of a single-plaquette model for SU(2)k and SU(3)k with naive cutoff and that based on the q-deformation to discuss cutoff dependence of the formulation.

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