Extensive multipartite entanglement from su(2) quantum many-body scars

TL;DR

This paper reveals that certain quantum many-body scar states exhibit extensive multipartite entanglement, demonstrated analytically and numerically, with implications for quantum metrology.

Contribution

It analytically and numerically shows that su(2) quantum many-body scars have extensive multipartite entanglement, expanding understanding of their structure and potential applications.

Findings

Exact scarred eigenstates show super-extensive quantum Fisher information.

Numerical simulations indicate dynamical generation of multipartite entanglement.

Scar states possess rich multipartite correlations useful for quantum metrology.

Abstract

Recent experimental observation of weak ergodicity breaking in Rydberg atom quantum simulators has sparked interest in quantum many-body scars - eigenstates which evade thermalisation at finite energy densities due to novel mechanisms that do not rely on integrability or protection by a global symmetry. A salient feature of some quantum many-body scars is their sub-volume bipartite entanglement entropy. In this work we demonstrate that such exact many-body scars also possess extensive multipartite entanglement structure if they stem from an su(2) spectrum generating algebra. We show this analytically, through scaling of the quantum Fisher information, which is found to be super-extensive for exact scarred eigenstates in contrast to generic thermal states. Furthermore, we numerically study signatures of multipartite entanglement in the PXP model of Rydberg atoms, showing that extensive quantum Fisher information density can be generated dynamically by performing a global quench experiment. Our results identify a rich multipartite correlation structure of scarred states with significant potential as a resource in quantum enhanced metrology.