  Formation of atomic pairs by the dissociation of a molecular condensate or by
inelastic collisions in an atomic condensate due to a time-dependent curve
crossing process is studied beyond the mean-field approximation. The number of
atoms formed by the spontaneous process is described by a Landau-Zener formula
multiplied by an exponential amplification factor due to quantum many-body
effects. The atomic pairs are formed in an entangled (squeezed) state. The rate
of stimulated processes depends on the relative phase of the two fields.
