04. June 2024

Our paper on the Onsager rgeression theorem has been published The quantum regression theorem has been verified for an optical quantum gas

A fundamental relation connecting the temporal fluctuations and the response behaviour has been experimentally observed in a quantum gas made of photons, the particles of light. The validity of this so-called quantum regression theorem could so far not be directly revealed for quantum gases.

Onsager Regression Theorem - Concept of the experiment: A condensate of photons (small sphere) is coupled to a large bath depicted by the red sphere. What happens to the condensate when the bath is disturbed, and how is this connected to the fluctuations of the bath? © J. Schmitt / Uni Bonn

Download all images in original size The impression in connection with the service is free, while the image specified author is mentioned.

The quantum regression theorem connects the fluctuations of a medium with its dissipative response to a perturbation. This theorem now has been shown to be valid in an optical quantum gas of light, a Bose-Einstein condensate of photons. The results have been published in Nature Communications.

Blog entry: Fluctuations and Response in a Quantum Gas of Light

University press release

Publication

Alexander Sazhin, Vladimir N. Gladilin, Andris Erglis, Göran Hellmann, Frank Vewinger, Martin Weitz, Michiel Wouters &
Julian Schmitt
Observation of nonlinear response and Onsager regression in a photon Bose-Einstein condensate.
Nature Communications 15, 4730 (2024).
https://doi.org/10.1038/s41467-024-49064-9