Experimental rectification of entropy production by a Maxwell's Demon in a quantum system

TL;DR

This paper demonstrates experimentally how a quantum Maxwell's demon can reduce entropy production by using information to control a quantum system, challenging traditional thermodynamic limits.

Contribution

It derives a new trade-off relation for information and thermodynamics in quantum systems and implements a quantum Maxwell's demon controlling another spin system.

Findings

Experimental implementation of a quantum Maxwell's demon.

Evidence of reduced irreversibility via information control.

Assessment of noise and protocol effectiveness.

Abstract

Maxwell's demon explores the role of information in physical processes. Employing information about microscopic degrees of freedom, this "intelligent observer" is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics. In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion. We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell's demon in a quantum system. The demon is experimentally implemented as a spin-1/2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1/2 system, through a natural interaction. Noise and imperfections in this protocol are investigated by the assessment of its effectiveness. This realization provides experimental evidence that the irreversibility on a non-equilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.