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Updated: Jun 17, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Three-color Sagnac source of polarization-entangled photon pairs
Michael Hentschel1, Hannes Hübel, Andreas Poppe
1Institute for Quantum Optics and Quantum Information - IQOQI, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria. michael.hentschel@ait.ac.at
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 1.13 x 10(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.
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