Intensity-intensity correlations and quantum interference in a driven three-level atom - art. no. 043410

We investigate the two-time intensity correlation functions of the fluoresc ence field emitted from a V-type three-level atom. We are particularly inte rested in the manner in which the atom emits photons in the presence of qua ntum interference. We show that under strong-field excitation quantum inter ference lends to anticorrelations of photons emitted from the atomic excite d levels which can exist for extremely long times. This indicates that the excited atomic levels are not the preferred radiative states. We find that the atom spends most of its time in a superposition of the excited atomic l evels from which it emits strongly correlated photons. The strong correlati ons are present only for a nonzero splitting between the excited levels, an d for degenerate levels the correlations reduce to that of a two-level atom . Moreover, we find that the transition from the ground level to the symmet ric superposition of the excited levels does nor saturate even for a strong driving field. We also calculate the correlation functions for a weak driv ing field, and find that in this case the photon correlations are not signi ficantly affected by quantum interference. but the atom can emit a strongly correlated pair of photons produced by a three-wave mixing process. Under appropriate conditions, with near-maximal quantum interference, it is possi ble to make the maximum value of the correlation function extremely large, in marked contrast with the corresponding case with no quantum interference .