The Resource Theory of Quantum States Out of Thermal Equilibrium

TL;DR

This paper develops a resource theory framework for quantum thermodynamics, showing that free energy naturally arises as a measure of useful work and state interconversion rates under energy-preserving transformations.

Contribution

It introduces a formal resource theory approach to quantum thermodynamics, linking free energy to resource conversion and work extraction.

Findings

Free energy quantifies useful work extractable from quantum states.

Resource interconversion rates are governed by free energy in the asymptotic limit.

The framework connects thermodynamic concepts with quantum information theory.

Abstract

The ideas of thermodynamics have proved fruitful in the setting of quantum information theory, in particular the notion that when the allowed transformations of a system are restricted, certain states of the system become useful resources with which one can prepare previously inaccessible states. The theory of entanglement is perhaps the best-known and most well-understood resource theory in this sense. Here we return to the basic questions of thermodynamics using the formalism of resource theories developed in quantum information theory and show that the free energy of thermodynamics emerges naturally from the resource theory of energy-preserving transformations. Specifically, the free energy quantifies the amount of useful work which can be extracted from asymptotically-many copies of a quantum system when using only reversible energy-preserving transformations and a thermal bath at fixed temperature. The free energy also quantifies the rate at which resource states can be reversibly interconverted asymptotically, provided that a sublinear amount of coherent superposition over energy levels is available, a situation analogous to the sublinear amount of classical communication required for entanglement dilution.