  We investigate the effects of spontaneous scattering on the evolution of
entanglement of two atomic samples, probed by phase shift measurements on
optical beams interacting with both samples. We develop a formalism of
conditional quantum evolutions and present a wave function analysis implemented
in numerical simulations of the state vector dynamics. This method allows to
track the evolution of entanglement and to compare it with the predictions
obtained when spontaneous scattering is neglected. We provide numerical
evidence that the interferometric scheme to entangle atomic samples is only
marginally affected by the presence of spontaneous scattering, and should thus
be robust even in more realistic situations.
