Non-local geometric phase in two-photon interferometry

Abstract

We report the experimental observation of the non-local geometric phase in Hanbury Brown-Twiss polarized intensity interferometry. The experiment involves two independent, polarized, 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 Poincaré 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 non-local 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.