QUANTUM EFFECTS VERSUS THE SEMICLASSICAL APPROXIMATION

We study a two-level quantum system interacting through a coupling strength g with a single-mode radiation field. We show that the rotating-wave-approximation (RWA) Hamiltonian produces quantum-mechanical effects more persistent than those generated by the full Hamiltonian. Within the full Hamiltonian the semiclassical prediction is recovered upon increase of the radiation field intensity, whereas with the RWA Hamiltonian no reconciliation with the predictions of the semiclassical approximation is realized by fields of any intensity, if the interaction strength g is kept unchanged.