Observing a quantum Maxwell demon at work

TL;DR

This paper demonstrates a quantum Maxwell demon using superconducting circuits that tracks quantum states, converts information into work, and measures entropy, illustrating the thermodynamics-information relationship in quantum systems.

Contribution

It presents the first experimental realization of a quantum Maxwell demon that operates with superconducting circuits, linking quantum information and thermodynamics.

Findings

Successfully measured work extraction in a quantum regime

Quantified entropy in the demon's memory

Illustrated the thermodynamics-information interplay in quantum systems

Abstract

In apparent contradiction to the laws of thermodynamics, Maxwell's demon is able to cyclically extract work from a system in contact with a thermal bath exploiting the information about its microstate. The resolution of this paradox required the insight that an intimate relationship exists between information and thermodynamics. Here, we realize a Maxwell demon experiment that tracks the state of each constituent both in the classical and quantum regimes. The demon is a microwave cavity that encodes quantum information about a superconducting qubit and converts information into work by powering up a propagating microwave pulse by stimulated emission. Thanks to the high level of control of superconducting circuits, we directly measure the extracted work and quantify the entropy remaining in the demon's memory. This experiment provides an enlightening illustration of the interplay of thermodynamics with quantum information.