Microcanonical thermodynamics in general physical theories

TL;DR

This paper extends microcanonical thermodynamics to general physical theories, establishing a framework with resource theories and characterizing state convertibility, revealing a duality with entanglement theory under certain conditions.

Contribution

It introduces a general microcanonical framework for arbitrary theories and analyzes three resource theories with a focus on sharp theories with purification.

Findings

Resource theories are hierarchically structured.

State convertibility is characterized by majorisation.

Duality with entanglement resource theory under unrestricted reversibility.

Abstract

Microcanonical thermodynamics studies the operations that can be performed on systems with well-defined energy. So far, this approach has been applied to classical and quantum systems. Here we extend it to arbitrary physical theories, proposing two requirements for the development of a general microcanonical framework. We then formulate three resource theories, corresponding to three different sets of basic operations: i) random reversible operations, resulting from reversible dynamics with fluctuating parameters, ii) noisy operations, generated by the interaction with ancillas in the microcanonical state, and iii) unital operations, defined as the operations that preserve the microcanonical state. We focus our attention on a class of physical theories, called sharp theories with purification, where these three sets of operations exhibit remarkable properties. Firstly, each set is contained into the next. Secondly, the convertibility of states by unital operations is completely characterised by a majorisation criterion. Thirdly, the three sets are equivalent in terms of state convertibility if and only if the dynamics allowed by theory satisfy a suitable condition, which we call unrestricted reversibility. Under this condition, we derive a duality between the resource theory of microcanonical thermodynamics and the resource theory of pure bipartite entanglement.