Quantum Many-Body Scar States with Emergent Kinetic Constraints and Finite-Entanglement Revivals

TL;DR

This paper constructs exact quantum many-body scar states in a nonintegrable spin-1/2 model relevant to Rydberg atom experiments, revealing emergent kinetic constraints and long-lived revivals distinct from previous scar models.

Contribution

It introduces a new solvable model exhibiting quantum many-body scars with emergent kinetic constraints, expanding understanding of nonthermal eigenstates in quantum systems.

Findings

Exact scar eigenstates with sub-volume-law entanglement

Persistent coherent oscillations after quantum quenches

Connection to Rydberg-blockaded atomic lattice states

Abstract

We construct a set of exact, highly excited eigenstates for a nonintegrable spin-1/2 model in one dimension that is relevant to experiments on Rydberg atoms in the antiblockade regime. These states provide a new solvable example of quantum many-body scars: their sub-volume-law entanglement and equal energy spacing allow for infinitely long-lived coherent oscillations of local observables following a suitable quantum quench. While previous works on scars have interpreted such oscillations in terms of the precession of an emergent macroscopic SU(2) spin, the present model evades this description due to a set of emergent kinetic constraints in the scarred eigenstates that are absent in the underlying Hamiltonian. We also analyze the set of initial states that give rise to periodic revivals, which persist as approximate revivals on a finite timescale when the underlying model is perturbed. Remarkably, a subset of these initial states coincides with the family of area-law entangled Rokhsar-Kivelson states shown by Lesanovsky to be exact ground states for a class of models relevant to experiments on Rydberg-blockaded atomic lattices.