Autonomous Maxwell's demon in a cavity QED system

Baldo-Luis Najera-Santos,Jean-Michel Raimond,Patrice A Camati,Alexia Auffèves,Michel Brune,Igor Dotsenko,Valentin Métillon

doi:10.1103/physrevresearch.2.032025

Abstract

We present an autonomous Maxwell's demon scheme. It is first analysed theoretically in term of information exchange in a closed system and then implemented experimentally with a single Rydberg atom and a high-quality microwave resonator. The atom simulates both a qubit interacting with the cavity, and a demon carrying information on the qubit state. While the cold qubit crosses the hot cavity, the demon prevents energy absorption from the cavity mode, apparently violating the second law of thermodynamics. Taking into account the change of the mutual information between the demon and the qubit-cavity system gives rise to a generalized expression of the second law that we establish and measure. Finally, considering the closed qubit-cavity-demon system, we establish and measure that the generalized second law can be recast into an entropy conservation law, as expected for a unitary evolution.

Highlights

Back in the 19th century, Clausius postulated that no spontaneous process exists whose sole result is the transfer of heat Qh from a cold bath to a hot bath [1]
Introducing the inverse temperatures, βc and βh, of the cold and hot baths, respectively, this empirical result is captured by the formula
It was later realized that Eq (1) is one of the many expressions of the second law of thermodynamics (SLT), with being the entropy produced during the heat transfer

Summary

Introduction

The atom simulates both a qubit interacting with the cavity and a demon carrying information on the qubit state. Taking into account the change of the mutual information between the demon and the qubit-cavity system gives rise to a generalized expression of the second law that we establish and measure.

Results

Conclusion