Our paper “Quantum Rabi dynamics of trapped atoms far in the deep strong coupling regime“ has been published in the journal Nature Communications. We report on a study of ultrastrong coupling between two mechanical modes of trapped cold atoms in the quantum Rabi regime. Using a novel experimental scheme, we achieve a Rabi coupling of 6.5 times the field mode frequency, so that the coupling term clearly dominates over all other energy scales for the first time.

The grand-canonical coupling of photons to a bath of dye molecules leads to fluctuations of the particle number. According to the fluctuation-dissipation theorem this is connected to a viscosity of the photon gas. In our experiment, we were able to prove the relation for a Bose-Einstein condesed gas for the first time.

Andreas Redmann presented his PhD project at the Excellence Slam of the university.

Our group members Steffi Moll and Niels Wolf presented experiments on the foundations of quantum physics in Regensburg.