Correlation approach to work extraction from finite quantum systems

TL;DR

This paper demonstrates that global operations for work extraction in finite quantum systems create quantum correlations, and it establishes conditions under which these outperform local operations based on classical correlations.

Contribution

It reveals the unavoidable quantum correlations generated by global operations and provides a necessary and sufficient condition for their advantage over local transformations.

Findings

Global operations necessarily create quantum discord.

Global transformations can outperform local gates in work extraction.

A condition based on classical correlations determines when global operations are superior.

Abstract

Reversible work extraction from identical quantum systems via collective operations was shown to be possible even without producing entanglement among the sub-parts. Here, we show that implementing such global operations necessarily imply the creation of quantum correlations, as measured by quantum discord. We also reanalyze the conditions under which global transformations outperform local gates as far as maximal work extraction is considered by deriving a necessary and sufficient condition that is based on classical correlations.