Characterization of single photons using two-photon interference
  Adiabatic passage techniques allow the generation of single photons which are very long compared to the typical detector time resolution. Therefore the detection time of a photon can be measured within the duration of the single-photon wavepacket. As a consequence, two-photon interference can be investigated in a time-resolved manner, i.e., the coincidence rate can be measured as a function of the time between photodetections. The theoretical analysis shows that this method not only gives information about the duration of single photons, but also about their coherence time. Here we discuss how to use this method for a spectral or temporal characterization of a single-photon source. 
T. Legero, T. Wilk, A. Kuhn, and G. Rempe