Revealing missing charges with generalised quantum fluctuation relations

TL;DR

This paper introduces a general protocol using quantum fluctuation relations to detect conserved charges in quantum many-body systems, aiding in understanding their dynamics and thermalization.

Contribution

It proposes a novel method to identify conserved quantities in quantum systems through exact fluctuation relations, applicable to quantum simulators.

Findings

Revealed charges influence quantum dynamics and thermalization.

Demonstrated unbiased temperature estimation from non-equilibrium data.

Applicable to driven quantum simulators and transition studies.

Abstract

The non-equilibrium dynamics of quantum many-body systems is one of the most fascinating problems in physics. Open questions range from how they relax to equilibrium to how to extract useful work from them. A critical point lies in assessing whether a system has conserved quantities (or 'charges'), as these can drastically influence its dynamics. Here we propose a general protocol to reveal the existence of charges based on a set of exact relations between out-of-equilibrium fluctuations and equilibrium properties of a quantum system. We apply these generalised quantum fluctuation relations to a driven quantum simulator, demonstrating their relevance to obtain unbiased temperature estimates from non-equilibrium measurements. Our findings will help guide research on the interplay of quantum and thermal fluctuations in quantum simulation, in studying the transition from integrability to chaos and in the design of new quantum devices.