Piston-Like Information Engine I: Universal Features in Equilibrium

TL;DR

This paper experimentally demonstrates a microscopic information engine using a colloidal suspension, revealing universal features in energy extraction from equilibrium through measurement-based control.

Contribution

It introduces a piston-like information engine that exploits measurement outcomes to control energy extraction, highlighting universal behavior in equilibrium systems.

Findings

Stored energy is universally determined by measurement probability.

Mechanical work can be extracted during piston decompression.

The system operates effectively without external work input.

Abstract

The ability to measure the stochastic degrees of freedom of a thermal system enables the extraction of energy from an equilibrium heat bath. This is the underlying principle of Maxwell's demon and subsequent information engines. Here, we experimentally realize a microscopic information engine configured as a compressible piston containing a thermalized colloidal suspension. The particle positions are recorded to identify when a predefined region near the wall is empty, allowing the piston to compress the colloidal suspension without applying work on the system. We find that the stored compression energy is universally set by the probability of a positive measurement outcome, which in turn is controlled by parameters such as density and compression step size. We further demonstrate that mechanical work can be extracted during the decompression of the piston, thereby closing the engine's operating cycle.