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Updated: May 22, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
A high-brightness source of polarization-entangled photons optimized for applications in free space
Fabian Steinlechner1, Pavel Trojek, Marc Jofre
1ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona), Spain. fabian.steinlechner@icfo.es
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.
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