Description of quantum coherence in thermodynamic processes requires constraints beyond free energy

TL;DR

This paper demonstrates that quantum coherence introduces additional thermodynamic constraints beyond free energy relations, highlighting the irreversibility of coherence transformations and their role as a fundamental resource.

Contribution

It introduces a new set of thermodynamic constraints based on quantum time-asymmetry, extending traditional free energy relations to include quantum coherence effects.

Findings

Quantum coherence imposes independent thermodynamic constraints.

Coherence transformations are inherently irreversible.

Relational coherence in multipartite systems can contribute to work.

Abstract

Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilard engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement.