Time-domain atom interferometry across the threshold for Bose-Einstein condensation - art. no. 170401

We have performed time-domain interferometry experiments with matter waves trapped in a harmonic potential above and below the Bose-Einstein phase tra nsition, by means of the method of separated oscillating fields, with a var iable time delay T. We observe the oscillations of the population between t wo internal Zeeman states versus the delay T to be rapidly depleted both be low and slightly above Bose-Einstein condensation. We give a quantitative e xplanation in terms of the phase evolution due to the entanglement between the internal and external degrees of freedom.