2026-10-26 · arXiv Quantum Physics
arXiv:2610.32154v1 Announce Type: new
Abstract: Measurements of photon-number-dependent time-of-arrival (TOA) distributions in wide NbN superconducting microstrip single-photon detectors (SMSPDs) are presented. Two \SI{10}{\um}-long devices with widths of \SI{3.2}{\um} and \SI{6.4}{\um} are characterized under pulsed \SI{515}{nm} excitation. The TOA histograms are described by sums of exponentially modified Gaussian (EMG) components, with the wider device exhibiting components assigned to photon numbers up to \(n=8\). Adjacent TOA peaks become more distinguishable relative to their widths at higher photon number, in contrast to the compression of neighboring photon-number timing shifts observed in conventional narrow-wire SNSPDs. For the components assigned to \(n=7\) and \(n=8\), the FWHM-normalized peak separation is \(2.15\), and the fitted EMG distributions yield an equal-prior pairwise TOA-assignment fidelity of \(99.6\%\). The EMG exponential-tail parameter \(\tau_n\) decreases strongly with photon number, while the Gaussian-location parameter \(\mu_n\) continues to shift between neighboring components. A phenomenological model motivated by absorption-site-dependent vortex processes and collective current redistribution captures these timing trends. These results support wide SMSPDs as a platform for TOA-based photon-number discrimination at high photon number, relevant to multiphoton-state characterization and photonic quantum information processing. The same geometry also provides a setting to examine how the spatial distribution of photon absorption affects vortex-assisted detection.
原文链接：https://arxiv.org/abs/2610.32154
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