Continuous Observation of Interference Fringes from Bose Condensates
  We use continuous measurement theory to describe the evolution of two Bose condensates in an interference experiment. It is shown how the system evolves in a single run of the experiment into a state with a fixed relative phase, while the total gauge symmetry remains unbroken. Thus, an interference pattern is exhibited without violating atom number conservation. 
J.I.Cirac (Universidad de Castilla-La Mancha), C.W.Gardiner (Victoria   University), M.Naraschewski (MPI f. Quantenoptik), a...