QUANTUM BEATS IN SPONTANEOUS EMISSION FROM 2 ATOMS IN A DETUNED SQUEEZED VACUUM

The time evolution of the populations of the collective states of a tw o-atom system in a squeezed vacuum can exhibit quantum beats. We show that the effect appears only when the carrier frequency of the squeeze d field is detuned from the atomic resonance. Moreover, we find that t he quantum beats are not present for the case in which the two-photon correlation strength is the maximum possible for a field with a classi cal analog. We also show that the population inversion between the exc ited collective states, found for the resonant squeezed vacuum, is sen sitive to the detuning and the two-photon correlations. For large detu nings or a field with a classical analog there is no inversion between the collective states. Observation of the quantum beats or the popula tion inversion would confirm the essentially quantum-mechanical nature of the squeezed vacuum. (C) 1997 Optical Society of America.