Ergotropy of quantum many-body scars

TL;DR

This paper investigates the ergotropy, or extractable energy, of quantum many-body scars in the PXP model, revealing their potential for quantum energy storage and battery applications.

Contribution

It demonstrates extensive ergotropy scaling in scar states, links ergotropy to entanglement, and proposes a protocol for energy extraction suitable for near-term quantum devices.

Findings

Scar states exhibit extensive ergotropy scaling.

A relation between ergotropy and entanglement is established.

A protocol for energy injection demonstrates potential for quantum batteries.

Abstract

Quantum many-body scars break ergodicity and evade thermalization, resulting in sub-volume law entanglement entropy even with high energy density. While their quantum correlations and entanglement have been elaborated previously, their capacity in storing extractable energy, quantified by the notion ergotropy, remains an open question. Here we focus on the representative PXP model, and unveil the extensive ergotropy scaling of a family of states interpolating between quantum many-body scars and thermal states, the latter of which are known to be passive with vanishing ergotropy in the thermodynamic limit. A phenomenological relation between ergotropy and entanglement is uncovered, which generalizes the existing free fermion integrable results to an interacting scenario. The ergotropy in a dynamical protocol shows that a reset with a global uniform coherent rotation can inject extractable energy, as a proof of principle way to charge a quantum "battery". Our protocol is tailored for near term Rydberg neutral atoms array, while also being feasible for other quantum processors. Our results establish that quantum many-body scars, despite the tiny fraction of the Hilbert space they occupy, can be efficiently exploited for storing extractable energy, and "scarring" a many-body system as a promising route for engineering quantum many-body battery.