Delayed single-photon self-interference — A double slit experiment in the time domain

Abstract

If a single photon is split into two wave-packets using a beam splitter and the two possible photon paths are made to overlap, an interference pattern due to interference between the two wave-packets can arise. If a classical detector, e.g. a photographic plate, is used for detecting the interference, the interference pattern will only be visible if the difference in length between the two possible photon paths is less than the coherence length of the photon wave-packet, i.e. the two wave-packets must overlap in both space and time. If however, instead of the normal detector, a material that can record and remember the phase of the electromagnetic field is placed in the region where the overlap takes place, it has been proposed that there can be interference even if the path difference is much larger than the coherence length of the photon [1], see Fig. 1 for a schematic experimental set-up. We denote this as ‘delayed single-photon self-interference’. In this case, the path difference still allowing interference to take place would only be limited by the phase memory time of the material. The interference of the photon wave-packets will be manifested as a frequency dependent population modulation in the material. The periodicity of this modulation is related to the time differences between the two possible photon paths. The frequency dependent modulation of the population is the time domain analogue to a spatial two-slit interference pattern. The fact that two non-overlapping wave packets can produce an interference pattern could be detected by diffracting a light pulse on the frequency modulated population.