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Q: Fachverband Quantenoptik und Photonik
Q 27: Quantum Gases: Bosons IV
Q 27.7: Vortrag
Dienstag, 24. März 2015, 16:00–16:15, P/H2
Phase coherence of a Bose-Einstein condensed light field — •Julian Schmitt1, Tobias Damm1, David Dung1, Christian Wahl1, Frank Vewinger1, Jan Klaers1,2, and Martin Weitz1 — 1Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn — 2Institute for Quantum Electronics, ETH Zürich, Auguste-Piccard-Hof 1, 8093 Zürich
In many physical systems, transitions between different phases of matter are accompanied by a spontaneous breaking of symmetry, as e.g. spin orientation in magnets and the corresponding breaking of rotational invariance. An ideal gas of bosons features a phase transition to a Bose-Einstein condensate, where a macroscopic fraction of particles is described by the single-particle wave function of the lowest energy eigenstate along with a spontaneously chosen, fixed phase. First-order spatio-temporal correlations of Bose condensates have been studied in e.g. atomic gases and exciton-polaritons. However, in-situ monitoring of the phase diffusion of a condensed system has proven challenging. Here, we present time-resolved measurements of the phase evolution of a photon Bose-Einstein condensate in dye microcavity, as obtained from heterodyne interferometry using a frequency-stable dye laser as a local oscillator. For increasing condensate fractions, a drastic reduction of the condensate linewidth is observed and first-order coherence is established. Further, we can relate first to second-order coherence properties, which are determined by the grand canonical nature of the photon condensate.