Sources of entanglement are an enabling resource in quantum technology, and pushing the limits of generation rate and quality of entanglement is a necessary pre-requisite towards practical applications. Here, we present an ultra-bright source of polarization-entangled photon pairs based on time-reversed Hong-Ou-Mandel interference. By superimposing four pair-creation possibilities on a polarization beam splitter, pairs of identical photons are separated into two spatial modes without the usual requirement for wavelength distinguishability or non-collinear emission angles. Our source yields high-fidelity polarization entanglement and high pair-generation rates without any requirement for active interferometric stabilization, which makes it an ideal candidate for a variety of applications, in particular those requiring indistinguishable photons.
@article{arxiv.1807.00383,
title = {Polarization entanglement by time-reversed Hong-Ou-Mandel interference},
author = {Yuanyuan Chen and Sebastian Ecker and Sören Wengerowsky and Lukas Bulla and Siddarth Koduru Joshi and Fabian Steinlechner and Rupert Ursin},
journal= {arXiv preprint arXiv:1807.00383},
year = {2019}
}