Multiplexed quantum frequency conversion

We study multiplexed quantum frequency conversion (m-QFC) on a single waveguide, where a single pump beam simultaneously converts multiple signal beams at distinct wavelengths. Using a three-peak periodically poled lithium niobate (PPLN) waveguide, we demonstrate the multiplexed upconversion in the telecom band with internal efficiencies up to 73.6%. Tested with a multichannel photon-pair source, the quantum correlation is preserved well after the conversion, with coincidence-to-accidental ratio reaching 767. These results highlight a viable device approach to multiplexed quantum key distribution, quantum sensing, and quantum computing.