High-fidelity quasideterministic entanglement generation using phase-matched spectral islands in a zero-added-loss multiplexing architecture

Photonic entanglement distribution is key for the emerging quantum internet. Here, the authors propose a spectral-multiplexing scheme that delivers favorable entanglement rates by combining domain-engineered crystals with zero-added-loss multiplexing. Their scheme uses a down-conversion crystal that can produce photon pairs in distinct, spectrally factorable ``islands'', and by combining same- and cross-island heralding, they dramatically reduce the number of required spectral channels.