Robust, high brightness, degenerate entangled photon source at room temperature

TL;DR

This paper presents a compact, robust, high-brightness entangled photon source operating at room temperature, achieving record pair production rates suitable for quantum communication applications.

Contribution

The authors demonstrate the highest photon pair rate using a bulk crystal at room temperature with a simple, stable setup based on PPKTP and a polarization Sagnac interferometer.

Findings

Photon pair rate of 39.13 MHz/mW at 810 nm

Bell inequality violation by nearly 10 standard deviations

Bell state fidelity of 0.96

Abstract

We report on a compact, simple and robust high brightness entangled photon source at room temperature. Based on a 30 mm long periodically poled potassium titanyl phosphate (PPKTP), the source produces non-collinear, type0 phase matched, degenerate photons at 810 nm with pair production rate as high 39.13 MHz per mW at room temperature. To the best of our knowledge, this is the highest photon pair rate generated using bulk crystals pump with continuous-wave laser. Combined with the inherently stable polarization Sagnac interferometer, the source produces entangled state violating the Bells inequality by nearly 10 standard deviations and a Bell state fidelity of 0.96. The compact footprint, simple and robust experimental design and room temperature operation, make our source ideal for various quantum communication experiments including long distance free space and satellite communications.