Optimal Work Extraction and the Minimum Description Length Principle

TL;DR

This paper links optimal work extraction in classical information engines to universal data compression, showing that driving the system to a critical state maximizes work and connects thermodynamics with information theory.

Contribution

It introduces a framework where the optimal non-equilibrium state is given by the maximum-likelihood distribution, connecting thermodynamics with universal coding theory.

Findings

Optimal non-equilibrium state is the maximum-likelihood distribution.

Work extracted is bounded by half the Shannon entropy of measurements.

Driving system to a critical state enhances optimal work extraction.

Abstract

We discuss work extraction from classical information engines (e.g., Szil\'ard) with $N$-particles, $q$ partitions, and initial arbitrary non-equilibrium states. In particular, we focus on their {\em optimal} behaviour, which includes the measurement of a set of quantities $\Phi$ with a feedback protocol that extracts the maximal average amount of work. We show that the optimal non-equilibrium state to which the engine should be driven before the measurement is given by the normalised maximum-likelihood probability distribution of a statistical model that admits $\Phi$ as sufficient statistics. Furthermore, we show that the minimax universal code redundancy $\mathcal{R}^*$ associated to this model, provides an upper bound to the work that the demon can extract on average from the cycle, in units of $k_{\rm B}T$. We also find that, in the limit of $N$ large, the maximum average extracted work cannot exceed $H[\Phi]/2$, i.e. one half times the Shannon entropy of the measurement. Our results establish a connection between optimal work extraction in stochastic thermodynamics and optimal universal data compression, providing design principles for optimal information engines. In particular, they suggest that: (i) optimal coding is thermodynamically efficient, and (ii) it is essential to drive the system into a critical state in order to achieve optimal performance.