Frequency multiplexed entangled photon pairs and detectors for quantum repeaters*

Large-scale entanglement-based quantum networks rely on efficient quantum repeaters that can distribute entanglement in a multi-mode and heralded fashion over multiple network nodes. Next to optical quantum memories, most quantum repeater architectures also require suitably multiplexed sources of entangled photon pairs as well as detectors that can distinguish between the different modes—including temporal, spatial and spectral modes— used to encode quantum information.

Here we demonstrate the generation and characterization of frequency multiplexed photon pairs at 795 nm (signal) and 1532 nm (idler) wavelength by employing cavity-enhanced spontaneous parametric down-conversion in a nonlinear crystal and a virtually-imaged phase array (VIPA) that allows mapping of spectral modes onto distinct spatial modes. Coincidence measurements reveal non-classical correlation between spectrally correlated signal and idler photons, with strongly reduced correlations between photons belonging to non-matched spectral channels. This demonstrates that both our photon-pair source as well as the novel detection setup are suitable for creating a frequency multiplexed quantum repeater