Non-local geometric phase in two-photon interferometry

TL;DR

This paper experimentally demonstrates a nonlocal geometric phase in two-photon interferometry, showing how coincidence counts between separated detectors can be controlled by the geometric phase, with implications for photonic entanglement manipulation.

Contribution

It provides the first experimental observation of a nonlocal geometric phase in two-photon interferometry using polarized incoherent sources.

Findings

Coincidence rates are controlled by the geometric phase.

Local measurements do not reveal the geometric phase.

The effect demonstrates a nonlocal control of photon correlations.

Abstract

We report the experimental observation of the nonlocal geometric phase in Hanbury Brown-Twiss polarized intensity interferometry. The experiment involves two independent, polar- ized, incoherent sources, illuminating two polarized detectors. Varying the relative polarization angle between the detectors introduces a geometric phase equal to half the solid angle on the Poincar\'e sphere traced out by a pair of single photons. Local measurements at either detector do not reveal the effect of the geometric phase, which appears only in the coincidence counts between the two detectors, showing a genuinely nonlocal effect. We show experimentally that coincidence rates of photon arrival times at separated detectors can be controlled by the two photon geometric phase. This effect can be used for manipulating and controlling photonic entanglement.