Origins and correction of secondary peaks in timing jitter of high-speed superconducting nanowire single-photon detectors

Superconducting nanowire single-photon detectors (SNSPDs) offer high detection speeds and excellent timing resolution, enabling numerous applications such as high-speed quantum communication and deep-space laser communication. However, at high count rates, timing jitter histograms deviate from a Gaussian profile and exhibit prominent secondary peaks, degrading jitter performance metrics such as full width at 10% maximum and full width at 1% maximum. This work identifies two distinct physical origins of these secondary peaks: multiphoton responses within a single excitation pulse and pulse pileup accompanied by time walk at high repetition rates. By experimentally isolating these mechanisms and applying corresponding statistical time-offset corrections, a near-Gaussian jitter distribution is restored. These results clarify the physics of secondary peaks in SNSPDs and provide a route to achieving simultaneous high counting rates and low timing jitter.