  Beyond the rotating-wave approximation, the dynamics of a quantum oscillator
interacting strongly and off-resonantly with a two-level system exhibit
beatings, whose period equals the revival time of the two-level system. On a
longer time scale, the quantum oscillator shows collapses, revivals and
fractional revivals, which are encountered in oscillator observables like the
mean number of oscillator quanta and in the two-level inversion population.
Also the scattered oscillator field shows doublets with symmetrically displaced
peaks.
