Quantum beats in two-atom resonance fluorescence.

Abstract

We study the resonance fluorescence emitted by two laser-driven coupled identical two-level atoms and allow for an arbitrary separation between the atoms and an arbitrary orientation of the interatomic axis in the laser field. Quantum beats arise in the resonance fluorescence intensity profile when an interatomic axis orientation is not perpendicular to the driving field propagation direction and are well resolved for an interatomic separation comparable to the resonant wavelength. These beats vanish for noninteracting atoms as well as for atoms separated by distances much smaller than the resonant wavelength. We also consider the time-dependent resonance fluorescence photon statistics that also exhibit quantum beats. Sub-Poissonian photon statistics occur for large interatomic separations and, for small separations, sub- and super-Poissonian statistics arise depending on the atomic orientation in the external driving field.