YQI Talk - Nathanaël Cottet - ENS Lyon, France

Event time: 
Thursday, March 21, 2019 - 11:00am to 12:00pm
YQI Seminar Room - 4th Floor See map
17 Hillhouse Ave
Event description: 

Observing a quantum Maxwell demon at work

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. Recent experiments have realized classical versions of elementary Maxwell demons in various physical systems. While quantum versions have long been investigated theoretically, experimental realizations are in their infancy and a full characterization is still missing. Here, we present the realization of 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. Importantly, we are able to directly probe the extracted work by measuring the output power emitted by the system through stimulated emission, without inferring it from system trajectories. We are thus able to demonstrate how the information stored in the demon’s memory affects the extracted work. To make the characterization complete, we also measure the entropy and energy of the system and the demon. Superconducting circuits thus reveal themselves as a suitable experimental testbed for the blooming field of quantum thermodynamics of information.