Collective operations can extremely reduce work fluctuations

TL;DR

This paper demonstrates that collective quantum operations can drastically reduce work fluctuations, enabling near-deterministic work extraction from multiple copies, surpassing the traditional 1/√N fluctuation decay.

Contribution

It introduces protocols where collective processing exponentially suppresses work fluctuations, improving the reliability of quantum work extraction.

Findings

Work fluctuations decay exponentially with the number of copies when processed collectively.

A significant portion of the average work can be extracted almost deterministically.

Applicable to both isolated systems and systems in thermal contact, enhancing quantum thermodynamic protocols.

Abstract

We consider work extraction from $N$ copies of a quantum system. When the same work-extraction process is implemented on each copy, the relative size of fluctuations is expected to decay as $1/\sqrt{N}$. Here, we consider protocols where the copies can be processed collectively, and show that in this case work fluctuations can disappear exponentially fast in $N$. As a consequence, a considerable proportion of the average extractable work $\mathcal{W}$ can be obtained almost deterministically by globally processing a few copies of the state. This is derived in the two canonical scenarios for work extraction: (i) in thermally isolated systems, where $\mathcal{W}$ corresponds to the energy difference between initial and passive states, known as the ergotropy, and (ii) in the presence of a thermal bath, where $\mathcal{W}$ is given by the free energy difference between initial and thermal states.