Multiplexing heralded single photons in orbital-angular-momentum space

Abstract

A heralded single-photon source (HSPS) with competitive single-photon purity and indistinguishability has become an essential resource for photonic quantum information processing. Here we propose a theoretical regime to enhance heralded single-photon generation by multiplexing the degree of freedom of orbital angular momentum (OAM) of down-converted entangled photon pairs emitted from a nonlinear crystal. Experimentally, a proof-of-principle experiment is performed through multiplexing three OAM modes. We achieve a $47%$ enhancement in the single-photon rate. A second-order autocorrelation function ${g}^{(2)}(0)<0.5$ ensures our multiplexed heralded single photons with good single-photon purity. We further indicate that an OAM-multiplexed HSPS with high quality can be constructed by generating higher-dimensional entangled states and sorting them with high efficiency in OAM space. Our method may approach a good HSPS with the deterministic property.