Post-selection free, integrated optical source of non-degenerate, polarization entangled photon pairs

TL;DR

This paper introduces a compact, integrated optical source for non-degenerate polarization-entangled photon pairs in the telecom band, utilizing engineered phase-matching in lithium niobate to achieve high brightness and strong quantum correlations.

Contribution

It presents a novel integrated, post-selection free source of polarization-entangled photon pairs with engineered phase-matching for non-degenerate pairs in the telecom regime.

Findings

Brightness of 7,000 pairs/(s mW GHz) achieved

Visibilities exceeding 95% in entanglement tests

Bell inequality violation with S=2.57±0.06

Abstract

We present an integrated source of polarization entangled photon pairs in the telecom regime, which is based on type II-phasematched parametric down-conversion (PDC) in a Ti-indiffused waveguide in periodically poled lithium niobate. The domain grating -- consisting of an interlaced bi-periodic structure -- is engineered to provide simultaneous phase-matching of two PDC processes, and enables the direct generation of non-degenerate, polarization entangled photon pairs with a brightness of $B=7\times10^3$ pairs/(s mW GHz). The spatial separation of the photon pairs is accomplished by a fiber-optical multiplexer facilitating a high compactness of the overall source. Visibilities exceeding 95% and a violation of the Bell inequality with $S=2.57\pm0.06$ could be demonstrated.