Jitter-reduction technique may lead to new communication protocols

Superconducting nanowire single-photon detectors, or SNSPDs, are essential components in many quantum and classical communication systems. When an SNSPD is illuminated by photons, the superconductor will transition abruptly to a normal conducting state, producing a voltage pulse in the process. By measuring the arrival time of the pulse, the arrival time of the photon can be measured.

But jitter, or the timing uncertainty in the photon arrival time measurement, must be controlled. Mueller et al. developed a means of calibration that correlates delays in detections with the time between pulses.

“The timing delays, caused by the detector firing while in a partially recovered state or by overlapping voltage pulses, can increase jitter at high count rates,” said author Andres Mueller. “Since these delays are deterministic, we have developed a method to measure them under specific conditions and use this calibration data to cancel out the delays in real-time.”

The increase in jitter at high rates originates from the intrinsic reset properties of the nanowire and properties of the amplification chain. The researchers chose to calibrate using a mode-locked laser that produces fast light pulses. They used the calibration data to correct added jitter with a look-up table correction method. Correcting in this way preserves original count rate and may work on a free-running, time-to-digital converter.

“Our work has significant potential for immediate impact, as it provides a way to improve the performance of existing SNSPD systems without the need for new hardware, aside from the laser used for calibration,” said Mueller.

Source: “Time-walk and jitter correction in SNSPDs at high count rates,” by Andrew Mueller, Emma E. Wollman, Boris Korzh, Andrew D. Beyer, Lautaro Narvez, Ryan Rogalin, Maria Spiropulu, and Matthew D. Shaw, Applied Physics Letters (2023). The article can be accessed at https://doi.org/10.1063/5.0129147 .