Three-color Sagnac source of polarization-entangled photon pairs

TL;DR

This paper presents a compact, stable, and high-brightness source of polarization-entangled photon pairs at 810 nm and 1550 nm wavelengths, suitable for quantum communication, using a novel Sagnac interferometer design that requires no active stabilization.

Contribution

The authors introduce a novel Sagnac-based interferometer design for generating polarization-entangled photon pairs without active stabilization, achieving high spectral brightness and fidelity.

Findings

Spectral brightness of 1.13x10^6 pairs/s/mW/THz.

Entanglement fidelity of 98.2%.

Photon pairs are fiber-coupled and suitable for quantum communication.

Abstract

We demonstrate a compact and stable source of polarization-entangled pairs of photons, one at 810 nm wavelength for high detection efficiency and the other at 1550 nm for long-distance fiber communication networks. Due to a novel Sagnac-based design of the interferometer no active stabilization is needed. Using only one 30 mm ppKTP bulk crystal the source produces photons with a spectral brightness of 1.13x10^6 pairs/s/mW/THz with an entanglement fidelity of 98.2%. Both photons are single-mode fiber coupled and ready to be used in quantum key distribution (QKD) or transmission of photonic quantum states over large distances.