Stochastic independence as a resource in small-scale thermodynamics

TL;DR

This paper demonstrates that in microscopic non-equilibrium thermodynamics, creating small amounts of correlations can significantly expand the set of possible state transformations, enabling work extraction close to the free energy limit.

Contribution

It reveals that creating minimal correlations among few auxiliary systems can bypass traditional constraints, broadening accessible transformations in microscopic thermodynamics.

Findings

Creating small correlations enables any transformation with decreasing free energy.

Only a few auxiliary systems are needed to extend transformation capabilities.

Work extraction can reliably reach the free energy limit in microscopic engines.

Abstract

It is well-known in thermodynamics that the creation of correlations costs work. It seems then a truism that if a thermodynamic transformation A->B is impossible, so will be any transformation that in sending A to B also correlates among them some auxiliary systems C. Surprisingly, we show that this is not the case for non-equilibrium thermodynamics of microscopic systems. On the contrary, the creation of correlations greatly extends the set of accessible states, to the point that we can perform on individual systems and in a single shot any transformation that would otherwise be possible only if the number of systems involved was very large. We also show that one only ever needs to create a vanishingly small amount of correlations (as measured by mutual information) among a small number of auxiliary systems (never more than three). The many, severe constraints of microscopic thermodynamics are reduced to the sole requirement that the non-equilibrium free energy decreases in the transformation. This shows that, in principle, reliable extraction of work equal to the free energy of a system can be performed by microscopic engines.