Quantum scarred eigenstates in a Rydberg atom chain: Entanglement, breakdown of thermalization, and stability to perturbations

By C. J. Turner, A. Michailidis, D. Abanin, Maksym Serbyn, Z. Papi'c. Physical review B, 2018

413 citations recorded by the source corpus.

Recent realization of a kinetically constrained chain of Rydberg atoms by Bernien et al., [Nature (London) 551, 579 (2017)] resulted in the observation of unusual revivals in the many-body quantum dynamics. In our previous work [C. J. Turner et al., Nat. Phys. 14, 745 (2018)], such dynamics was attributed to the existence of “quantum scarred” eigenstates in the many-body spectrum of the experimentally realized model. Here, we present a detailed study of the eigenstate properties of the same model. We find that the majority of the eigenstates exhibit anomalous thermalization: the observable expectation values converge to their Gibbs ensemble values, but parametrically slower compared to the predictions of the eigenstate thermalization hypothesis (ETH). Amidst the thermalizing spectrum, we identify nonergodic eigenstates that strongly violate the ETH, whose number grows polynomially with system size. Previously, the same eigenstates were identified via large overlaps with certain product states, and were used to explain the revivals observed in experiment. Here, we find that these eigenstates, in addition to highly atypical expectation values of local observables, also exhibit subthermal entanglement entropy that scales logarithmically with the system size. Moreover, we identify an additional class of quantum scarred eigenstates, and discuss their manifestations in the dynamics starting from initial product states. We use forward scattering approximation to describe the structure and physical properties of quantum scarred eigenstates. Finally, we discuss the stability of quantum scars to various perturbations. We observe that quantum scars remain robust when the introduced perturbation is compatible with the forward scattering approximation. In contrast, the perturbations which most efficiently destroy quantum scars also lead to the restoration of “canonical” thermalization.

Subfields: Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/82e0e320de59e25549177a29f2d9ac421935daed

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Localization from Hilbert space shattering: From theory to physical realizations (2020, background): “Still more recently, a new type of counterexample to strong ETH has been observed, which now goes under the name of “quantum many-body scars” [24–43].”
Quantum many-body scars and weak breaking of ergodicity (2020, methodology): “Instead, different schemes have been used to approximate scarred eigenstates in the PXP model starting from |Z2〉 product state [16, 61].”
Statistical localization: From strong fragmentation to strong edge modes (2019, background): “Several works investigated the possibility of mimicking similarly localized behavior without explicitly breaking translation invariance [25–33], as well as the possibility of intermediate behavior, such as the existence of a small number of ETH-violating eigenstates within an otherwise generic spect”
Ergodicity Breaking Arising from Hilbert Space Fragmentation in Dipole-Conserving Hamiltonians (2019, background): “Restricted to the lowest energy subspace with no adjacent excited states, the dimension of the constrained Hilbert space can be shown to be [42] dL = FL+2 for open (OBC) —in the presence of additional boundary terms [104]— and dL = FL−1 + FL+1 for periodic boundary conditions (PBC), where Fn is the ”
Quantum simulation and computing with Rydberg-interacting qubits (2020, background): “This model and its variants have been theoretically studied in 1D 225,230–232 and more recently 2D on diﬀerent lattices 233,234 and found to exhibit liquid like ground states 230 , interacting Fi-bonacci anyons 231 and quantum scars (particular states that do not thermalize) 225,229,232 and…”
Quantum Many-Body Scars: A Quasiparticle Perspective (2022, methodology): “(151) found that the scar states also have anomalously low entanglement relative to other eigenstates of the PXP model at the same energy density, with half-chain entanglement entropy scaling ∼ lnL.”
Prediction of Toric Code Topological Order from Rydberg Blockade (2020, background): “[50] C.”
Signatures of integrability in the dynamics of Rydberg-blockaded chains (2018, background): “[24, 40]) at H0 are thus a finite-size shadow of the low-entropy conserved sectors in the proximate integrable parent model.”