  We consider the evolution of a two-level system coupled to a photon field
initially in a coherent state, as the energy of the two-level system is
linearly varied through resonance with the photon field. At a fixed time after
the resonance, the amplitude of the photon field is found to show a collapse
and subsequent revivals as a function of rate of energy variation. Including
decay of the photon field, we find that the observation of such collapse and
revivals is near the technological limit of current cavity QED experiments but
should be achievable.
