  Lithium-Niobate-On-Insulator (LNOI) is emerging as a promising platform for
integrated quantum photonic technologies because of its high second-order
nonlinearity, small waveguide footprint, and ultra-low propagation loss in a
broad wavelength range. Importantly, LNOI allows for creating electro-optically
reconfigurable circuits, which can be efficiently operated at cryogenic
temperature. Their integration with superconducting nanowire single-photon
detectors (SNSPDs) paves the way for realizing scalable photonic devices for
active manipulation and detection of quantum states of light. Here we report
the first realization of these two essential components in a single LNOI
photonic circuit. As an experimental showcase of our technology, we demonstrate
the combined operation of an electrically tunable Mach-Zehnder interferometer -
a fundamental building block for the realization of reconfigurable optical
networks - and two waveguide-integrated SNSPDs at its outputs. Our results
provide blueprints for implementing complex quantum photonic devices on a LNOI
platform.
