A high-brightness source of polarization-entangled photons optimized for applications in free space

TL;DR

This paper introduces a highly efficient, high-brightness source of polarization-entangled photons optimized for free-space applications, achieving high photon pair rates and fidelity with a simple setup.

Contribution

The authors demonstrate a novel, efficient entangled photon source using PPKTP crystals with high pair rates and fidelity, suitable for free-space quantum communication.

Findings

Generated 0.64 million photon pairs per second per milliwatt

Achieved an overlap fidelity of 0.98 with the Bell state

Utilized a simple, efficient SPDC setup with PPKTP crystals

Abstract

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.