A Scalable Single-Photon Detector Array Based on Superconducting Nanowires

Detecting single photons over large numbers of spatial modes is crucial for photonic quantum information processing. This measurement usually requires an array of time-resolved single-photon detectors. The superconducting nanowire single-photon detectors (SNSPDs) are currently the leading single-photon counting technology in the infrared wavelength and have the highest performance in timing jitter, detection efficiency, and counting rate. In a conventional readout scheme, each SNSPD requires one coaxial cable in the cryostat, a low-noise RF amplifier, and a high-resolution time-to-digital converter. Implementing a system of a few SNSPD channels with the conventional readout is possible, but scaling them to tens or hundreds of channels requires formidable resources and remains an outstanding challenge.

Here, we report a scalable two-terminal SNSPD array that only requires one pair of RF cables for the readout. We can show the architecture of the array, where a chain of detectors was connected using superconducting nanowire delay lines. The nanowire delay lines were designed to be slow-wave transmission lines with a phase velocity of only 0.016c, where c is the speed of light in vacuum. When a detector absorbs a photon and fires, it generates a pair of counter- propagating pulses towards the two terminals. By registering the pulses on the two terminals, and performing simple timing logic, one can resolve the arrival locations of up to two incident photons. By analyzing the electrical pulse shapes, we also showed photon-number-resolving capability in a 4-element device. This device architecture will be useful for multi-photon coincidence detection in photonic integrated circuits.