SPIE Proceedings 12009-66: Multi-channel waveguide-integrated superconducting nanowire single-photon detector system for ultrafast quantum key distribution

Upcoming quantum technologies require scalable and cost-efficient technical solutions for widespread functionality. The branch of quantum optics focuses on the interaction of light and matter and besides the creation and manipulation, the detection of single photons is one of the key features that are necessary to perform quantum experiments. Here, we present a low-footprint plug-and-play multi-channel single-photon detector system featuring integrated photonics that allows for ultra-fast quantum key distribution (QKD). Each channel comprises a superconducting nanowire single-photon detector (SNSPD) patterned from a niobium-titanium nitride (NbTiN) superconducting film atop silicon nitride waveguide structures.(1) Subsequently, the photonic circuitry interfaced via broadband 3D polymeric fiber-to-chip couplers(2) to the ports of an 8x8 channel fiber array. The readout electronics allow for time correlated single photon counting (TCSPC) of up to 64 channels simultaneously. In a QKD transmission experiment, a pair of the system's detection channels achieves secret key rates of up to 2.5 Mbit/s employing a coherent one-way (COW) protocol.(3)