Exact many-body scars and their stability in constrained quantum chains

Surace, Federica Maria; Votto, Matteo; Lazo, Eduardo González; Silva, Alessandro; Dalmonte, Marcello; Giudici, Giuliano

doi:10.1103/physrevb.103.104302

Cited by 43 publications

(23 citation statements)

References 48 publications

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“…A promising solution is to exploit quantum many-body scarring (QMBS) states that were first discovered in a 51 Rydberg-atom chain [14] and explained based on the effective PXP model [15,16]. While breaking the thermalization rendered ergodicity, the QMBS states are distinct from the quantum states in classically integrable systems and from quantum many-body localized states as well [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…For example, superconducting circuits of two-dimensional qubit array [5,48] with the advantages of high density integration and flexible controllability [49,50] can emulate many models with a broad tunable range of local couplings in a single device. In this regard, the experimentally observed QMBS states in the atomic platform are specific with respect to the constrained model [14,16,51]. The superconducting platform enables the QMBS states in disparate many-body systems (e.g., the Heisenberg spin system [52], among others) to be studied in a more in-depth and comprehensive way.…”

Section: Introductionmentioning

confidence: 99%

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Many-body Hilbert space scarring on a superconducting processor

Zhang¹,

Dong²,

Gao³

et al. 2022

Preprint

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Thermalization in complex and strongly interacting quantum many-body systems represents an obstacle to applications. It was recently suggested theoretically that quantum many-body scarring (QMBS) states embedded in the thermalized energy spectrum can overcome this difficulty. Here, by programming a superconducting circuit of two-dimensional multiqubit array with tunable couplings, we experimentally investigate the slow quantum thermalization dynamics associated with QMBS states in the paradigmatic settings of chain and comb tensor topologies, which are effectively described by the unconstrained spin model. Robust QMBS states have been successfully observed in a superconducting circuit of up to 30 qubits with an extraordinarily large Hilbert space for exact diagonalization simulations of classical computers. The QMBS states can be readily distinguished from the conventional thermalized states through the population dynamics, the entanglement entropy, and the fidelity, paving the way to exploiting these states for mitigating quantum thermalization for significant applications in quantum information science and technology.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Many-body Hilbert space scarring on a superconducting processor

Zhang¹,

Dong²,

Gao³

et al. 2022

Preprint

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“…S2 and S4), which confirms that periodic revivals of OTOCs are general phenomena for initial states within the scarred subspace, not some fine-tuned results. We attribute the unusual revival dynamics inside the light cone to the local rather than global thermalization argued above and robustness of scarred eigenstates against local perturbations: The quantum many-body scars have been shown to present certain robustness against perturbations and disorders [50][51][52][53][54]. Under some local perturbations like the σ x(z) i(j) operators (e −iH t σ x 1 |ψ ), thermalization happens locally and propagates outwards.…”

Section: (B) For a Sketch]mentioning

confidence: 86%

“…Conclusions and discussions.-In summary, we have numerically calculated the information scrambling dynamics in quantum many-body scarred systems, and found a new paradigm (a linear light cone and periodic oscillations inside the light cone) intrinsically different from the previously studied ETH or MBL cases. Analytical explanations based on perturbation-type calculations are provided [65], yet we expect this work to inspire subsequent in-depth analytical studies, from the perspectives such as Hilbert space fragmentation [46,47,[84][85][86], connections to the classical OTOC and chaos theory [32-34, 65, 87, 88], robustness of scarred eigenstates under perturbations [50][51][52][53][54], black hole physics [89,90], and information scrambling dynamics in other many-body scarred systems [13]. The two criteria, OTOCs and Holevo information, support each other and have been demonstrated to have measurable signatures with current experimental technologies.…”

Section: (B) For a Sketch]mentioning

confidence: 99%

Quantum Information Scrambling in Quantum Many-body Scarred Systems

Yuan,

Zhang,

Wang

et al. 2022

Preprint

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Quantum many-body scarred systems host special non-thermal eigenstates which support periodic revival dynamics and weakly break the ergodicity. In this paper, we study the quantum information scrambling dynamics in quantum many-body scarred systems, with a focus on the "PXP" model. We use the out-of-time-ordered correlator (OTOC) and Holevo information as measures of the information scrambling, and apply an efficient numerical method based on matrix product operators to compute them up to 41 spins. We find that both the OTOC and Holevo information exhibit a linear light cone and periodic oscillations inside the light cone for initial states within the scarred subspace, which is in sharp contrast to thermal or many-body localized systems. To explain the formation of the linear light cone structure, we provide a perturbation-type calculation based on a phenomenological model. In addition, we demonstrate that the OTOC and Holevo information dynamics of the "PXP" model can be measured using the Rydberg-atom quantum simulators with current experimental technologies, and numerically identify the measurable signatures using experimental parameters.

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“…Nowadays exact quantum many-body scars (QMBSs) and their stability in constrained quantum chains attract attention [15]. Quantum scars are nonthermal eigenstates characterized by low entanglement entropy, initially detected in systems subject to nearest neighbor Rydberg blockade, the PXP model [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Quantum Many-Body Scars in Spin-1 Kitaev Chains

You,

Zhao,

Ren

et al. 2022

Preprint

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To provide a physical example of quantum scars, we study the many-body scars in the spin-1 Kitaev chain where the so-called PXP Hamiltonian is exactly embedded in the spectra. Regarding the conserved quantities, the Hilbert space is fragmented into disconnected subspaces and we explore the associated constrained dynamics. The continuous revivals of the fidelity and the entanglement entropy when the initial state is prepared in |Z k (k = 2, 3) state illustrate the essential physics of the PXP model. We study the quantum phase transitions in the one-dimensional spin-1 Kitaev-Heisenberg model using the density-matrix renormalization group and Lanczos exact diagonalization methods, and determine the phase diagram. We parametrize the two terms in the Hamiltonian by the angle φ, where the Kitaev term is K ≡ sin(φ) and competes with the Heisenberg J ≡ cos(φ) term. One finds a rich ground state phase diagram as a function of the angle φ. Depending on the ratio K/J ≡ tan(φ), the system either breaks the symmetry to one of distinct symmetry broken phases, or preserves the symmetry in a quantum spin liquid phase with frustrated interactions. We find that the scarred state is stable for perturbations which obey Z2-symmetry, while it becomes unstable against Heisenberg-type perturbations.

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Exact many-body scars and their stability in constrained quantum chains

Cited by 43 publications

References 48 publications

Many-body Hilbert space scarring on a superconducting processor

Many-body Hilbert space scarring on a superconducting processor

Quantum Information Scrambling in Quantum Many-body Scarred Systems

Quantum Many-Body Scars in Spin-1 Kitaev Chains

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