Quantum states of Bose-Einstein condensates formed by molecular dissociation

We analyze the atomic state obtained by photodissociation of a molecular condensate. The process is not amenable to the usual mean-field description, and we base our analysis on approximate equations for the second moments of the atomic field operators and on Monte Carlo simulations derived from a positive-P phase-space description of the system. Our calculations show that the dissociation process produces an atomic condensate in a squeezed state in analogy with the down-conversion process lending to squeezed light in quantum optics. Atomic interactions lead to a threshold similar to the one in optical down-conversion, and to an atomic Kerr effect, which ultimately deteriorates the degree of squeezing.