High-rate classical and quantum communication using modulated mode locked laser source with low jitter SNSPDs

With high efficiency (>70%), sub-Hz dark count rate, and timing jitter below 15ps, the latest differential-readout Superconducting Nanowire Single Photon Detectors are best used with novel light sources to demonstrate their true potential. We report on the compelling abilities and applications of a high rate modulated mode locked laser testbed paired with these high performance SNSPDs. By synchronizing a variable repetition rate telecom-band mode locked laser with high speed lithium niobate modulators, we generate ultrashort laser pulses with extinction ratio beyond 60 dB. Detecting these pulses over a high loss channel with low timing jitter opens the door to previously undemonstrated Pulse Position Modulation (PPM) on a 20 GHz clock, a promising advance on the path towards high rate deep space optical communication.We demonstrate PPM encoding characterized by channel capacity metrics that approach theoretical limits. This testbed and detector infrastructure also forms the basis for ongoing high rate quantum commutation research. By pumping a pair generation crystal with the modulated laser we aim to demonstrate entanglement distribution with repetition rates beyond 5 GHz. With this, we set the foundation for practical high rate entanglement-based QKD and teleportation.