Noncommuting conserved charges in quantum thermodynamics and beyond

TL;DR

This paper explores how noncommuting conserved charges influence quantum thermodynamics, revealing complex effects on thermalization, entropy, and foundational principles, and highlighting open questions in the field.

Contribution

It provides a comprehensive survey of recent results and open problems regarding the impact of noncommuting charges on quantum thermodynamic phenomena.

Findings

Noncommuting charges can invalidate traditional thermal state derivations.

They may decrease entropy production in certain scenarios.

Evidence suggests noncommuting charges both hinder and enhance thermalization.

Abstract

Thermodynamic systems typically conserve quantities ("charges") such as energy and particle number. The charges are often assumed implicitly to commute with each other. Yet quantum phenomena such as uncertainty relations rely on observables' failure to commute. How do noncommuting charges affect thermodynamic phenomena? This question, upon arising at the intersection of quantum information theory and thermodynamics, spread recently across many-body physics. Charges' noncommutation has been found to invalidate derivations of the thermal state's form, decrease entropy production, conflict with the eigenstate thermalization hypothesis, and more. This Perspective surveys key results in, opportunities for, and work adjacent to the quantum thermodynamics of noncommuting charges. Open problems include a conceptual puzzle: Evidence suggests that noncommuting charges may hinder thermalization in some ways while enhancing thermalization in others.