  We find that the phase-space representation of the electromagnetic field
inside a driven cavity strongly coupled to a two-level atom can be employed to
distinguish photon emissions along a ladder of dressed states sustaining a
two-photon resonance. The emissions are told apart by means of the different
quantum beats generated by the conditional states they prepare. Sample quantum
trajectories explicitly reveal the difference in the transient due to the
initial condition, in a background set by the Jaynes-Cummings spectrum and
revealed by the strong-coupling limit. Their ensemble-averaged evolution is
tracked for a time period similar to that waited for the loss of a next photon
as the maximum non-exclusive probability, indicated by the peak of the
intensity correlation function.
