Phase diffusion of Bose-Einstein Condensation close to zero temperature
  The correlation function of the quantum fluctuations due to collective excitations is calculated and used to investigate the phase diffusion of a Bose-Einstein condensate close to zero temperature. It is shown that the phase diffusion time of the condensate is much longer than the result obtained by assuming that the correlation time of the quantum fluctuations is infinity. 
Hongwei Xiong, Shujuan Liu, Guoxiang Huang