Interference in a two-mode Bose system with $N$ particles is typical
  When a Bose-Einstein condensate is divided into two parts, that are subsequently released and overlap, interference fringes are observed. We show here that this interference is typical, in the sense that most wave functions of the condensate, randomly sampled out of a suitable ensemble, display interference. We make no hypothesis of decoherence between the two parts of the condensates. 
P. Facchi, H. Nakazato, S. Pascazio, F. V. Pepe, K. Yuasa
quant-ph cond-mat.quant-gas