Collinear source of polarization-entangled photon pairs at non-degenerate wavelengths

TL;DR

This paper presents a highly efficient, collinear source of polarization-entangled photon pairs at non-degenerate wavelengths, achieving high fidelity and rate, suitable for quantum communication and metrology.

Contribution

It introduces a simple, fully collinear configuration that enables high coupling efficiency, long nonlinear crystals, and high entanglement fidelity using a free-running laser diode.

Findings

Achieved 99.4% entanglement fidelity.

Reached 27,000 pairs/sec per mW pump rate.

Enabled use of long nonlinear crystals with high efficiency.

Abstract

We report on a simple but highly efficient source of polarization-entangled photon pairs at non-degenerate wavelengths. The fully collinear configuration of the source enables very high coupling efficiency into a single optical mode and allows the use of long nonlinear crystals. With optimized dispersion compensation it is possible to use a free-running laser diode as pump source and to reach an entanglement fidelity of 99.4 % at rates as high as 27000 pairs/s per mW of pump power. This greatly enhances the practicality of the source for applications in quantum communication and metrology.