We describe an interferometric method to uncover the quantum state eld. The
information needed to retrieve the corresponding Fock coefficients is impr
inted on the quantized longitudinal motion of atoms that have interacted wi
th the cavity held. In particular, we show that a set of four atomic moment
um distributions can be analyzed easily to reconstruct used to explain the
various regimes of output coupling BECs using radiation sources. We present
specific calculations of the rates of output coupling as a function of the
number of Bose atoms in the condensate and the frequency, detuning, and in
tensity of the radio-frequency field. [S1050-2947(99)00805-7].