A folded-sandwich polarization-entangled two-color photon pair source with large tuning capability for applications in hybrid quantum systems

Abstract

We demonstrate a two-color entangled photon pair source which can be adapted easily to a wide range of wavelength combinations. A Fresnel rhomb as a geometrical quarter-wave plate and a versatile combination of compensation crystals are key components of the source. Entanglement of two photons at the Cs D1 line (894.3 nm) and at the telecom O-band (1313.1 nm) with a fidelity of (Formula presented.) is demonstrated, and improvements of the setup are discussed.