Spontaneous creation and persistence of ground-state coherence in a   resonantly driven intra-cavity atomic ensemble
  The spontaneous creation and persistence of ground-state coherence in an ensemble of intracavity Rb atoms has been observed as a quantum beat. Our system realizes a quantum eraser, where the detection of a first photon prepares a superposition of ground-state Zeeman sublevels, while detection of a second erases the stored information. Beats appear in the time-delayed photon-photon coincidence rate (intensity correlation function). We study the beats theoretically and experimentally as a function of system parameters, and find them remarkably robust against perturbations such as spontaneous emission. Although beats arise most simply through single-atom-mediated quantum interference, scattering pathways involving pairs of atoms interfere also in our intracavity experiment. We present a detailed model which identifies all sources of interference and accounts for experimental realities such as imperfect pre-pumping of the atomic beam, cavity birefringence, and the transit of atoms across the cavity mode. 
D. G. Norris (1), A. D. Cimmarusti (1), L. A. Orozco (1), P.   Barberis-Blostein (2) and H. J. Carmichael (3) ((1) Joint Qua...
physics.atom-ph quant-ph