Twin Photon Correlations in Single-Photon Interference

TL;DR

This paper demonstrates a novel method to generate and analyze single-photon interference fringes using twin photons, enabling measurement of photon wavelength and momentum correlation without coincidence detection.

Contribution

It introduces a new technique for measuring two-photon correlations through single-photon interference patterns, avoiding traditional coincidence detection methods.

Findings

Fringes shift with optical path changes of undetected photons.

Photon wavelength can be inferred without direct detection.

Momentum correlation affects fringe visibility, enabling its measurement.

Abstract

We show that it is possible to generate a novel single-photon fringe pattern by using two spatially separated identical bi-photon sources. The fringes are similar to the ones observed in a Michelson interferometer and possess certain remarkable properties with potential applications. A striking feature of the fringes is that although the pattern is obtained by detecting only one photon of each photon pair, the fringes shift due to a change in the optical path traversed by the undetected photon. The fringe shift is characterized by a combination of wavelengths of both photons, which implies that the wavelength of a photon can be measured without detecting it. Furthermore, the visibility of the fringes diminishes as the correlation between the transverse momenta of twin photons decreases: visibility is unity for maximum momentum correlation and zero for no momentum correlation. We also show that the momentum correlation between the two photons of a pair can be determined from the single-photon interference pattern. We thus for the first time propose a method of measuring a two-photon correlation without coincidence or heralded detection.