Long-Range Coherence in Bose-Einstein Condensates

Moritz Schutte

Sean S. Hodgman, R. G. Dall, Andrew Manning +2 more

A major advance in understanding the behavior of light was to describe the coherence of a light source by using correlation functions that define the spatio-temporal relationship between pairs and larger groups of photons. Correlations are also a fundamental property of matter. We performed simultaneous measurement of the second- and third-order correlation functions for atoms. Atom bunching in the arrival time for pairs and triplets of thermal atoms just above the Bose-Einstein condensation (BEC) temperature was observed. At lower temperatures, we demonstrated conclusively the long-range coherence of the BEC for correlation functions to third order, which supports the prediction that like coherent light, a BEC possesses long-range coherence to all orders.

Elena Kammann, Hamid Ohadi, Maria Maragkou +4 more

In this work we study thermalisation-, coherence- and spin dynamics of photon and polariton Bose-Einstein condensates (BECs). We witness carrier distributions following the Bose Einstein distribution, buildup of long-range order and spontaneous symmetry breaking.

A. ROHRL H. WALLIS

Stephan Ritter, Anton Öttl, Tobias Donner +3 more

We have experimentally investigated the formation of off-diagonal long-range order in a gas of ultracold atoms. A magnetically trapped atomic cloud prepared in a highly nonequilibrium state thermalizes and thereby crosses the Bose-Einstein condensation phase transition. The evolution of phase coherence between different regions of the sample is constantly monitored and information on the spatial first-order correlation function is obtained. We observe the growth of the spatial coherence and the formation of long-range order in real time and compare it to the growth of the atomic density. Moreover, we study the evolution of the momentum distribution during the nonequilibrium formation of the condensate.