Tower of quantum scars in a partially many-body localized system

Iversen, Michael; Nielsen, Anne E. B.

doi:10.1103/physrevb.107.205140

Cited by 6 publications

(4 citation statements)

References 83 publications

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“…While the disorder strength was assumed to be sufficiently weak in this work such that the system overall remains chaotic, the versatility of our setup allows direct access to strong ergodicity-breaking regimes, where many-body localization was recently proposed to give rise to "inverted scarring" phenomena (41)(42)(43). More generally, our work bridges the gap between theoretical studies of QMBS, which place the emphasis on exact constructions of scarred eigenstates (16,17), and experimental realizations, e.g., in Rydberg atom arrays (18,19) or optical lattices (21), in which the scarred states are not known exactly [apart from a few exceptions (44)].…”

Section: Discussionmentioning

confidence: 99%

Disorder-tunable entanglement at infinite temperature

Dong,

Desaules,

Gao

et al. 2023

Sci. Adv.

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Emerging quantum technologies hold the promise of unravelling difficult problems ranging from condensed matter to high-energy physics while, at the same time, motivating the search for unprecedented phenomena in their setting. Here, we use a custom-built superconducting qubit ladder to realize non-thermalizing states with rich entanglement structures in the middle of the energy spectrum. Despite effectively forming an “infinite” temperature ensemble, these states robustly encode quantum information far from equilibrium, as we demonstrate by measuring the fidelity and entanglement entropy in the quench dynamics of the ladder. Our approach harnesses the recently proposed type of non-ergodic behavior known as “rainbow scar,” which allows us to obtain analytically exact eigenfunctions whose ergodicity-breaking properties can be conveniently controlled by randomizing the couplings of the model without affecting their energy. The on-demand tunability of quantum correlations via disorder allows for in situ control over ergodicity breaking, and it provides a knob for designing exotic many-body states that defy thermalization.

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Section: Discussionmentioning

confidence: 99%

Disorder-tunable entanglement at infinite temperature

Dong,

Desaules,

Gao

et al. 2023

Sci. Adv.

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“…Scarring initial states, on the other hand, do not spread significantly and maintain periodic proximity to eigenstates. They also have a discrete distribution of expansion coefficients (see figure 4(b)) caused by towers of scars in the energy spectrum [36]. The combination of these effects enables the phases to be distinguished by the distance measure which exhibits periodic revival behaviour for scar dynamics, as shown in figure 4(a).…”

Section: Dimensionality Reduction Of Qmbsmentioning

confidence: 99%

Unsupervised learning of quantum many-body scars using intrinsic dimension

Cao,

Angelakis,

Leykam

2024

Mach. Learn.: Sci. Technol.

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Quantum many-body scarred systems contain both thermal and non-thermal scar eigenstates in their spectra. When these systems are quenched from special initial states which share high overlap with scar eigenstates, the system undergoes dynamics with atypically slow relaxation and periodic revival. This scarring phenomenon poses a potential avenue for circumventing decoherence in various quantum engineering applications. Given access to an unknown scar system, current approaches for identification of special states leading to non-thermal dynamics rely on costly measures such as entanglement entropy. In this work, we show how two dimensionality reduction techniques, multidimensional scaling and intrinsic dimension estimation, can be used to learn structural properties of dynamics in the PXP model and distinguish between thermal and scar initial states. The latter method is shown to be robust against limited sample sizes and experimental measurement errors.

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“…is also eigenstates of H 0 , which share the same energy with y ñ | n . Studies have shown that quantum scars can be generated through towers [19,42,43]. Additionally, research indicates that introducing perturbations into the Heisenberg model can transition the system from integrable to chaotic, while the towers persist [44].…”

Section: Model Hamiltonian and Precise Towersmentioning

confidence: 99%

“…It is expected that there are exceptional cases where some special slowly thermalizing initial states retain the memory over longer periods of time. Specifically, it is well established that some nonintegrable systems can fail to thermalize due to rare nonthermal eigenstates called quantum many-body scars (QMBS) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . These nonthermal states are typically excited ones and span a subspace, in which any initial states do not thermalize and can return periodically.…”

Section: Introductionmentioning

confidence: 99%

Stable dynamic helix state in the nonintegrable XXZ Heisenberg model

Zhang,

Song

2024

Phys. Scr.

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We investigate the influence of external fields on the stability of spin helix states in an XXZ Heisenberg model. Exact diagonalization on a finite system shows that random transverse fields in the x and y directions drive the transition from integrability to nonintegrability. In such a system, the helix state can be regarded as a quantum scar. Simultaneously, the presence of uniform z field enables the helix state to better maintain its dynamical nature, allowing for a clearer understanding of its evolutionary behavior. However, the entanglement entropy reveals that irrespective of the presence of a uniform z field, as long as the system remains chaotic, the scar extent of the helix state shows no significant variation.

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Tower of quantum scars in a partially many-body localized system

Cited by 6 publications

References 83 publications

Disorder-tunable entanglement at infinite temperature

Disorder-tunable entanglement at infinite temperature

Unsupervised learning of quantum many-body scars using intrinsic dimension

Stable dynamic helix state in the nonintegrable XXZ Heisenberg model

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