Characterization of single photons using two-photon interference

Publisher summary: This chapter discusses the nature of single-photon light fields, the interference of two photons on a beam splitter and introduces the time-resolved two-photon interference. It presents how a frequency and an emission-time jitter affect the results of a time-resolved two-photon interference experiment. On this basis, the experimental characterization of a single-photon source, based on an adiabatic passage technique, is discussed. The time-resolved two-photon interference experiments are an excellent tool to characterize single photons. In these experiments, two photons are superimposed on a beam splitter and the joint detection probability in the two output ports of the beam splitter is measured as a function of the detection-time difference of the photons. This is only possible if the photons are long compared to the detector time resolution. For identical photons, the joint detection probability is expected to be zero. Variations of the spatiotemporal modes of the photons lead to joint photo detections except for zero detection-time difference. Therefore, the joint detection probability shows a pronounced dip. From the width of this dip, one can estimate the maximum emission-time jitter and the minimum coherence time of the photons. In addition, a lower limit of the single-photon duration can be obtained. This is not possible by just measuring the average detection probability with respect to the trigger producing the photons. Moreover, the chapter shows that a frequency difference between photons leads to a distinct oscillation in the joint detection probability