Mainz 2017 – scientific programme

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SYAD: Symposium SAMOP Dissertation-Prize 2017

SYAD 1: SAMOP Dissertation-Prize

SYAD 1.3: Invited Talk

Wednesday, March 8, 2017, 12:00–12:30, RW 1

Dynamics and correlations of a Bose-Einstein condensate of light — •Julian Schmitt — Institut für Angewandte Physik, Universität Bonn

Large statistical number fluctuations are a fundamental property of the thermal behavior of bosons. At low temperatures and high densities however, when a gas of bosons undergoes Bose-Einstein condensation, large fluctuations of the condensate population for a closed system are damped out and coherence emerges. On the other hand, for a Bose-Einstein condensate coupled to an environment, i.e. in the presence of a very large reservoir, drastic modifications of the coherence properties have been predicted, though not yet experimentally observed. In my talk, I will describe measurements of the photon number correlations and phase correlations of a Bose-Einstein condensate of photons generated in a dye microcavity. In this system, the photo-excitable dye molecules act as a heat and particle reservoir for the photons, which in the condensed state allows to reach a regime with number fluctuations approaching the size the total particle number, as predicted by grand canonical statistical theory. Experimentally, effective photon reservoirs of different size can be engineered. For the first time this has allowed to experimentally demonstrate Bose-Einstein condensation at grand canonical statistical ensemble conditions, with its characteristic non-vanishing Hanbury-Brown Twiss correlations in the condensed phase. An intriguing feature of this regime is the occurrence of discrete phase jumps of the macroscopic wave function, allowing to in-situ monitor the spontaneous symmetry breaking of the condensate.