  Quantum effects in a system of coupled atomic and molecular Bose-Einstein
condensates in the framework of a two-mode model are studied numerically and
analytically, using the discrete WKB approach. In contrast to the mean-field
approximation, the WKB analytical results are in a very good agreement with
numerical results. The quantum fluctuations of the atomic and molecular
populations are calculated, and found to be of the same order of magnitude as
their mean values.
