Interference of overlap-free entangled photons with a Mach-Zehnder-like interferometer

TL;DR

This paper demonstrates that polarization-entangled photon pairs can produce interference fringes with half-wavelength periodicity in a modified Mach-Zehnder interferometer, regardless of photon separation, advancing quantum measurement techniques.

Contribution

It introduces a novel experimental setup showing interference of entangled photons with a Mach-Zehnder interferometer, independent of photon separation distance.

Findings

Interference fringes with half-wavelength periodicity observed

Entangled photons maintain interference independent of separation

Potential applications in quantum-enhanced measurement

Abstract

Using spontaneous parametric down conversion and a 50:50 beam splitter, we generate coaxial polarization-entangled photon pairs, of which the two photons are far separated from each other. The photons are then sent one by one through one port of a modified Mach-Zehnder interferometer. We observe interference fringes with a periodicity half of the single-photon wavelength, independent of the distance between the photons. This feature can find applications in quantum-enhanced measurement.