Freiburg 2024 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 9: Bosonic Quantum Gases II (joint session Q/A)
Q 9.1: Talk
Monday, March 11, 2024, 17:00–17:15, Aula
Regression theorem and nonlinear response in a photon Bose-Einstein condensate — Alexander Sazhin1, Vladimir N. Gladilin2, Andris Erglis3, Frank Vewinger1, Martin Weitz1, Michiel Wouters2, and •Julian Schmitt1 — 1Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany — 2TQC, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium — 3Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany
The quantum regression theorem states that the correlations of a system at two different times are governed by the same equations of motion as the temporal response of the average values. Here we report experiments demonstrating that the two-time second-order correlations of a photon Bose-Einstein condensate inside a dye-filled microcavity exhibit the same eigenvalues of the dynamics as the response of the condensate to a sudden perturbation of the dye molecule bath. This confirms an unconventional form of the regression theorem for a coupled many-body quantum system, where the perturbation acts on the bath and only the condensate response is monitored. For strong perturbations, we observe nonlinear relaxation dynamics well described by microscopic theory, confirming the regression theorem for an optical quantum gas also beyond the regime of linear response.
Keywords: Bose-Einstein condensation; Nonequilibrium dynamics; Open quantum systems