Perturbative corrections to photon coincidence spectroscopy
  Photon coincidence spectroscopy is a promising technique for probing the nonlinear regime of cavity quantum electrodynamics in the optical domain, however its accuracy is mitigated by two factors: higher-order photon correlations, which contribute to an enhanced pair count rate, and non-simultaneity of emitted photon pairs from the optical cavity. We show that the technique of photon coincidence spectroscopy is effective in the presence of these effects if the quantitative predictions are adjusted to include non-simultaneity and higher-order correlations. 
L. Horvath, B. C. Sanders