COHERENCE OF BOSE CONDENSATES

We study the coherence of interacting Bose condensates in recent magne tic trap experiments. The coherent evolution manifests itself in the m acroscopic interference of two independent Bose condensates. The theor etical predictions from the time-dependent Gross-Pitaevskii equation a re in excellent agreement with the measured interference patterns. A c oherent coupling of two condensates represents the atomic analogon of a Josephson junction. The dependence of the magnetic confinement on th e nuclear spin orientation allows one to build a controllable beam spl itter by magnetic resonance. The application of this beam splitter to realize an atom laser is studied theoretically. The coherence of the o utput beam is limited only by phase diffusion of the condensate.