The thermodynamic meaning of negative entropy

TL;DR

This paper explores how quantum information can lead to negative entropy, allowing for work gain during erasure and potential cooling, extending Landauer's principle into quantum regimes.

Contribution

It generalizes Landauer's principle to quantum information, demonstrating that negative entropy enables work extraction during erasure.

Findings

Negative entropy can occur in quantum systems.

Work can be gained during erasure due to negative entropy.

System erasure can result in environmental cooling.

Abstract

Landauer's erasure principle exposes an intrinsic relation between thermodynamics and information theory: the erasure of information stored in a system, S, requires an amount of work proportional to the entropy of that system. This entropy, H(S|O), depends on the information that a given observer, O, has about S, and the work necessary to erase a system may therefore vary for different observers. Here, we consider a general setting where the information held by the observer may be quantum-mechanical, and show that an amount of work proportional to H(S|O) is still sufficient to erase S. Since the entropy H(S|O) can now become negative, erasing a system can result in a net gain of work (and a corresponding cooling of the environment).