Superconducting nanowire detector jitters limited by detector geometry

TL;DR

This paper demonstrates that the detection timing jitter in superconducting nanowire single photon detectors is partly caused by geometric factors related to the wire's length and area, and introduces a differential cryogenic readout to reduce jitter.

Contribution

The study introduces a novel differential cryogenic readout method that reduces geometric jitter in SNSPDs, improving timing accuracy for photon detection.

Findings

Jitter increases with detector size, reaching up to 50 ps for 20 μm x 20 μm devices.

Differential readout reduces jitter by approximately 20% in large SNSPDs.

Geometric jitter is confirmed as a significant factor through experiments with long, narrowed wire regions.

Abstract

Detection jitter quantifies variance introduced by the detector in the determination of photon arrival time. It is a crucial performance parameter for systems using superconducting nanowire single photon detectors (SNSPDs). In this work, we have demonstrated that the detection timing jitter is limited in part by the spatial variation of photon detection events along the length of the wire. This distribution causes the generated electrical pulses to arrive at the readout at varied times. We define this jitter source as geometric jitter since it is related to the length and area of the SNSPD. To characterize the geometric jitter, we have constructed a novel differential cryogenic readout with less than 7 ps of electronic jitter that can amplify the pulses generated from the two ends of an SNSPD. By differencing the measured arrival times of the two electrical pulses, we were able to partially cancel out the difference of the propagation times and thus reduce the uncertainty of the photon arrival time. Our experimental data indicates that the variation of the differential propagation time was a few ps for a 3 {\mu}m x 3 {\mu}m device while it increased up to 50 ps for a 20 {\mu}m x 20 {\mu}m device. In a 20 {\mu}m x 20 {\mu}m large SNSPD, we achieved a 20% reduction in the overall detection timing jitter for detecting telecom-wavelength photons by using the differential cryogenic readout. The geometric jitter hypothesis was further confirmed by studying jitter in devices that consisted of long wires with 1-{\mu}m-long narrowed regions used for sensing photons.