BOSE-EINSTEIN CONDENSATE IN A DOUBLE-WELL POTENTIAL AS AN OPEN QUANTUM SYSTEM

We study the dynamics of a Bose-Einstein condensate in a double-well p otential in the two-mode approximation. The dissipation of energy from the condensate is described by the coupling to a thermal reservoir of noncondensate modes. As a consequence of the coupling, the self-locke d population imbalance in the macroscopic quantum self-trapping decays away. We show that a coherent state predicted by spontaneous symmetry breaking is not robust and decoheres rapidly into a statistical mixtu re due to the interactions between condensate and noncondensate atoms. However, via stochastic simulations we find that with a sufficiently fast measurement rate of the relative phase between the two wells the matter wave coherence is established even in the presence of the decoh erence.