Single photon sources and applications

We discuss sources of single photons for quantum information processing. For limited applications the attenuated laser is an adequate source. Further improvement would be obtained from single atom or molecule emission. Collection efficiency into a narrow band and single mode could be improved by photonic bandgap material surrounding the emitter. We discuss a measurement showing light emission from single dye molecules modified by planar cavity. Another source could be time gated single photons created from the parametric downconversion process. We go on to show a simple interference effect between separate single photons that confirms the quantum nature of this source.