  We present a numerical study comparing semiclassical and quantum models of a
damped, strongly interacting cavity QED system composed of a single two-level
atom interacting with a single quantized cavity mode driven externally by a
tunable monochromatic field. We compute the steady state transmission spectrum
of the coupled system under each model and show that in the strong coupling
regime, the two models yield starkly different results. The fully quantum
mechanical model of the system correctly yields the expected multiphoton
transmission spectra while the semiclassical approach results in a bistable
spectrum.
