Many-body Hilbert space scarring on a superconducting processor

Zhang, Pengfei; Dong, Hua; Gao, Yu; Zhao, Liangtian; Huang, Jie; Guo, Qiujiang; Chen, Jiachen; Deng, Jinfeng; Liu, Bobo; Ren, Wenhui; Yao, Yuan; Zhang, Xu; Xu, Shen; Wang, Ke; Jin, Feitong; Zhu, Xuhao; Li, Hekang; Chen, Song; Wang, Zhen; Fangli, Liu,; Papić, Zlatko; Lü, Ying; Hai, Wang,; Lai, Ying–Cheng

doi:10.48550/arxiv.2201.03438

Cited by 3 publications

(4 citation statements)

References 51 publications

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“…Instead, there are several outliers just below the band of thermal states. This kind of phenomenology has already been seen in other models with inexact scars [76,77]. As S is increased, the towers seem to get denser, without any clear state at the top even relatively close to the edges of the spectrum.…”

Section: S(s + 1)supporting

confidence: 65%

Prominent quantum many-body scars in a truncated Schwinger model

Desaules¹,

Hudomal²,

Banerjee³

et al. 2022

Preprint

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The high level of control and precision achievable in current synthetic quantum matter setups has enabled first attempts at quantum-simulating various intriguing phenomena in condensed matter physics, including those probing thermalization or its absence in closed quantum systems. In a recent work [Desaules et al., arXiv:2203.08830], we have shown that quantum many-body scarsspecial low-entropy eigenstates that weakly break ergodicity in nonintegrable systems-arise in spin-S quantum link models that converge to (1 + 1)−D lattice quantum electrodynamics (Schwinger model) in the Kogut-Susskind limit S → ∞. In this work, we further demonstrate that quantum many-body scars exist in a truncated version of the Schwinger model, and are qualitatively more prominent than their counterparts in spin-S quantum link models. We illustrate this by, among other things, performing a finite-S scaling analysis that strongly suggests that scarring persists in the truncated Schwinger model in the limit S → ∞. Although it does not asymptotically converge to the Schwinger model, the truncated formulation is relevant to synthetic quantum matter experiments, and also provides fundamental insight into the nature of quantum many-body scars, their connection to lattice gauge theories, and the thermalization dynamics of the latter. Our conclusions can be readily tested in current cold-atom setups.

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Section: S(s + 1)supporting

confidence: 65%

Prominent quantum many-body scars in a truncated Schwinger model

Desaules¹,

Hudomal²,

Banerjee³

et al. 2022

Preprint

Self Cite

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“…Introduction.-Quantum many-body scars (QMBS) form an intriguing paradigm of ergodicity breaking in interacting systems that are typically expected to thermalize due to their nonintegrability and spatial homogeneity [1][2][3][4][5]. QMBS comprise eigenstates of low entanglement entropy [6,7], many of which reside in the middle of the spectrum, and are often separated roughly equally in energy [8,9].…”

mentioning

confidence: 99%

Weak Ergodicity Breaking in the Schwinger Model

Desaules¹,

Banerjee²,

Hudomal³

et al. 2022

Preprint

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As a paradigm of weak ergodicity breaking in disorder-free nonintegrable models, quantum manybody scars (QMBS) can offer deep insights into the thermalization dynamics of gauge theories. Having been first discovered in a spin-1/2 quantum link formulation of the Schwinger model, it is a fundamental question as to whether QMBS persist for S > 1/2 since such theories converge to the lattice Schwinger model in the large-S limit, which is the appropriate version of lattice QED in one spatial dimension. In this work, we address this question by exploring QMBS in spin-S U(1) quantum link models (QLMs) with staggered fermions. We find that QMBS persist at S > 1/2, with the resonant scarring regime, which occurs for a zero-mass quench, arising from simple high-energy gauge-invariant initial states. We furthermore find evidence of detuned scarring regimes, which occur for finite-mass quenches starting in the physical vacua and the charge-proliferated state. Our results conclusively show that QMBS exist in a wide class of lattice gauge theories in one spatial dimension represented by spin-S QLMs coupled to dynamical fermions.

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“…Such eigenstates have been found in a variety of contexts, including the Affleck-Kennedy-Lieb-Tasaki (AKLT) model [20,21], ensembles of Rydberg atoms [22][23][24][25], and various other interacting spin [26][27][28][29][30][31][32][33][34], bosonic [35], and fermionic [36][37][38] models. These eigenstates can also give rise to coherent periodic dynamics from certain initial states, which has allowed QMBS to be observed in quantum simulation experiments [22,25,39,40].…”

Section: Introductionmentioning

confidence: 99%

“…In the first case, the aim is to time-evolve a superposition of scarred states that exhibits periodic dynamics in the unperturbed limit and extract the lifetime of the observed oscillations. In many cases of interest, a product state is sufficient for these purposes and the state preparation is therefore trivial [22,23,25,26,34,35,39,40,50]. However, in other cases, the simplest superposition of scar states is area-law entangled and has a nontrivial MPS representation with a finite correlation length [27,51,52], and here some thought must be put into the most efficient method to prepare such states.…”

Section: Introductionmentioning

confidence: 99%

Preparing quantum-many body scars on a quantum computer

Gustafson,

Li,

Kahn

et al. 2023

Preprint

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Quantum many-body scar states are highly excited eigenstates of many-body systems that exhibit atypical entanglement and correlation properties relative to typical eigenstates at the same energy density. Scar states also give rise to infinitely long-lived coherent dynamics when the system is prepared in a special initial state having finite overlap with them. Many models with exact scar states have been constructed, but the fate of scarred eigenstates and dynamics when these models are perturbed is difficult to study with classical computational techniques. In this work, we propose state preparation protocols that enable the use of quantum computers to study this question. We present protocols both for individual scar states in a particular model, as well as superpositions of them that give rise to coherent dynamics. For superpositions of scar states, we present both a system-size-linear depth unitary and a finite-depth nonunitary state preparation protocol, the latter of which uses measurement and postselection to reduce the circuit depth. For individual scarred eigenstates, we formulate an exact state preparation approach based on matrix product states that yields quasipolynomial-depth circuits, as well as a variational approach with a polynomial-depth ansatz circuit. We also provide proof of principle state-preparation demonstrations on superconducting quantum hardware.

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Many-body Hilbert space scarring on a superconducting processor

Cited by 3 publications

References 51 publications

Prominent quantum many-body scars in a truncated Schwinger model

Prominent quantum many-body scars in a truncated Schwinger model

Weak Ergodicity Breaking in the Schwinger Model

Preparing quantum-many body scars on a quantum computer

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