Abstract

We study the coherence fluctuations in a Josephson junction created by two weakly coupled Bose-Einstein condensates. We apply the two-mode approximation in the full quantum theory analysis, and so that the system is described by a two-site Bose-Hubbard Hamiltonian. The coherence fluctuations are determined by the total number of particles N, charging energy E_C, junction energy E_J, asymmetry δ and temperature T. For zero-temperature symmetric systems, the coherence fluctuations increase with E_C/E_J, however, the number squeezing increases with N²E_C/E_J. For zero-temperature asymmetric systems, the coherence fluctuations are suppressed by the balance effects between asymmetry and interparticle interaction and the single-atom resonance effects. The coherence fluctuations grow with temperature, and the formation of a self-trapping state will cause abnormal behaviors at high temperatures.

© 2007 Optical Society of America