Coherence and measurement in quantum thermodynamics

TL;DR

This paper explores how quantum coherence influences thermodynamic work during quantum measurements, revealing fundamental differences from classical erasure and impacting quantum thermodynamics frameworks.

Contribution

It identifies quantum-specific projections that require coherence for non-trivial thermodynamic work, advancing understanding of quantum measurement thermodynamics.

Findings

Quantum coherence enables work in certain quantum projections.

Classical and quantum erasure have similar thermodynamic costs.

Implications for quantum fluctuation relations and single-shot thermodynamics.

Abstract

Thermodynamics is a highly successful macroscopic theory widely used across the natural sciences and for the construction of everyday devices, from car engines and fridges to power plants and solar cells. With thermodynamics predating quantum theory, research now aims to uncover the thermodynamic laws that govern finite size systems which may in addition host quantum effects. Here we identify information processing tasks, the so-called "projections", that can only be formulated within the framework of quantum mechanics. We show that the physical realisation of such projections can come with a non-trivial thermodynamic work only for quantum states with coherences. This contrasts with information erasure, first investigated by Landauer, for which a thermodynamic work cost applies for classical and quantum erasure alike. Implications are far-reaching, adding a thermodynamic dimension to measurements performed in quantum thermodynamics experiments, and providing key input for the construction of a future quantum thermodynamic framework. Repercussions are discussed for quantum work fluctuation relations and thermodynamic single-shot approaches.