Achieving Photon Number Resolution with Linearly Multiplexed Single-Photon Detectors

This work studies a photon-number resolving detector (PNRD) made by a linearly multiplexed single-photon niobium nitride detector (SPD) array integrated on a silicon nitride strip-loaded waveguide platform, fabricated on a lithium niobate on insulator (LNOI) substrate. Linearity allows the device to maintain the mathematical model for the fidelity of already existing spatially multiplexed SPDs, while significantly changing the detector’s geometry. Integrating such a device on a LNOI platform allows to exploit the unique properties of lithium niobate, such as the high electro-optic effect. Additionally, niobium nitride SPDs are one of the best superconductor devices available nowadays, allowing for tunable, and overall high, detection efficiency and low dark counts rate, making them one of the best candidates for our platform.