Can a Photon Be Separated from Its Wave?

Abstract

An experiment is proposed in which the overall path taken by a photon is indicated by the timing of a twin herald photon, while a particular segment of that path is determined by interference. The needed coincident pairs of photons are generated by type I spontaneous-parametric-down-conversion (SPDC) and diffraction selected by a grating at the frequency of a two-photon state. This is to be divided into two one-photon states of high coherence length. Upon experimental confirmation that their count coincidences have been maintained, the one-photon sources are to be used as a timing herald and source for an unequal path interferometer. A photon’s path through the interferometer via a short arm is indicated by count synchronization with the herald. The exit output port used and resulting final detection location are determined by the phase in the long arm. If output port usage can be controlled by the phase in the photon-free arm, the path of the photon as particle will have been controlled by interference with an accompanying photon-empty wave.