Two-photon interference of temporally separated photons

TL;DR

This paper experimentally demonstrates two-photon interference with temporally separated photons in different interferometer setups, revealing complex interference phenomena and advancing understanding of quantum interference effects.

Contribution

It introduces a method to observe two-photon interference with temporally separated photons in a single interferometric setup, combining Hong-Ou-Mandel and path-entangled interference effects.

Findings

Observation of two-photon interference fringes with temporally separated photons

Simultaneous demonstration of Hong-Ou-Mandel and path-entangled interference

Enhanced understanding of interference origins in spatially bunched/anti-bunched states

Abstract

We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms.