The first single photon sources and single photon interference experiments

Abstract

This chapter shows how the concept of single-photon sources has emerged, in the mid 1980s. We emphasize the difference between “single-photon wave-packets” and attenuated classical light pulses or light beams. The quantum behavior of single photons—they cannot yield more than one photodetection—is contrasted with the behavior of attenuated classical light, which always yields some possibility of a joint detection on both sides of a beam splitter. We describe the single-photon source that we developed in the mid 1980s at Institut d’Optique, as well as the quantitative criterion (“anticorrelation”) that we introduced to show that it was indeed a single-photon source. We contrast these results with the ones that we obtained with a source of classical light pulses produced by a strongly attenuated light emitting diode, in which the average number of photons per pulse was much less than 1. We also describe the interference experiment we carried out with our single-photon source, illustrating the notion of wave-particle duality. We conclude with a brief overview of further developments in sources of single-photons, heralded or on-demand, as well as in wave-particle duality experiments, in particular Wheeler’s delayed choice experiments.