  Quantum collapses and revivals are fascinating manifestations of
interference. Of particular interest in recent years are macroscopic quantum
interference effects in Bose-Einstein condensates. In this letter such effects
will be studied for the two site Bose-Hubbard model that is a standard model
for exploration of Bose-Einstein condensates. An analytic expression that is
valid in the weak coupling limit for the difference in the occupation of the
two sites is developed and tested numerically. It describes correctly the
collapses and revivals. Moreover, it is demonstrated that a calculation to the
first order in the interparticle interaction is required for the prediction of
the collapse and revival times while the second order is required for the
evaluation of the shape of the revival peaks. We believe that the result is
relevant for a variety of situations where collapses and revivals are found.
