High-resolution coincidence counting system for large-scale photonics applications

Abstract: The increasing complexity of the recent photonic experiments challenges developing efficient multi-channel coincidence counting systems with high-level functionality. Here, we report a coincidence unit able to count detection events ranging from singles to 16-fold coincidences with full channel-number resolution. The device operates within sub-100~ps coincidence time windows, with a maximum input frequency of 1.5~GHz and an overall jitter of less than 10~ps. The unit high-level timing performance renders it suitable for quantum photonic experiments employing low-timing-jitter single-photon detectors. Additionally, the unit can be used in complex photonic systems to drive feed-forward loops. We have demonstrated the developed coincidence counting unit in photon-number-resolving detection to directly quantify the statistical properties of light, specifically coherent and thermal states, with a fidelity exceeding 0.999 up to 60~photons.