Optical readout of a superconducting single photon detector with a cryogenic modulator

The realisation of light modulation based on single photon detection events is an important step towards feed-forward-modulation, which is required for many quantum optics protocols. This requires combining detection events with modulation in a device with a small physical footprint, for which integrated optics is ideal. Several platforms for integrated quantum optics have been developed to generate, modulate, and detect quantum features in the light over the last years. Titanium in-diffused waveguides in lithium niobate is a promising candidate for quantum communication applications [1] , [2] , however, single photon detection with superconducting photon detectors (SNSPDs) require cryogenic temperatures. Therefore, optimising the nonlinear optical properties of these waveguides under cryogenic operating conditions is an important task. Previously, we have demonstrated frequency conversion [3] , electro-optical modulation [4] and integrated single photon detection [5] at cryogenic temperatures.