Assessment of the Bundle SNSPD Plus FPGA-Based TDC for High-Performance Time Measurements

Counting single photons and measuring their arrival time is of crucial importance for imaging and quantum applications that use single photons to outperform classical techniques. The investigation of the coincidence, i.e. correlation, between photons can be used to enhance the resolution of optical imaging techniques or to transmit information using quantum cryptography. Time measurements at the state-of-the-art are performed using Superconducting Nanowire Single Photon Detectors (SNSPDs), the lowest timing jitter single-photon detectors, connected to digital oscilloscopes or digitizers. This method is not well adapted to the ever-increasing and pressing requirement to perform measurements on a high number of channels at the same time. We focus the high-performance measure of the arrival time of photons and their correlation by means of SNSPDs and a 16-channel Time-to-Digital Converter fully implemented in Field Programmable Gate Array (FPGA). In this approach, the photons' coincidence is analyzed in real-time directly in the FPGA, resulting in a Coincidence Time Resolution (CTR) of 22.8 ps r.m.s.. For the practical benefit of the scientific community, an extended and comprehensive panorama also of comparison with the actual available strategies in this field of applications is offered through a huge number of references.