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  • Open Access

Extracting photon-number information from superconducting nanowire single-photon detectors traces via mean-derivative projection

I. S. Kuijf1,*, F. B. Baalbergen2,*, L. Seldenthuis2,*, E. P. L. van Nieuwenburg1, and M. J. A. de Dood2,†

  • 1Lorentz Institute and Leiden Institute of Advanced Computer Science, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands
  • 2Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands

  • *These authors contributed equally to this work.
  • †Contact author: dood@physics.leidenuniv.nl
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APS Open Sci. 1, 000073 – Published 28 July, 2026

DOI: https://doi.org/10.1103/dwth-wjtr

Abstract

Photon-number-resolved detection with superconducting nanowire single-photon detectors (SNSPDs) attracts increasing interest, often focusing on the rising edge of the electrical signal as the main source of photon-number-resolving information. It remains unclear whether additional photon-number information is contained in the rest of the detector response and how this can be optimally extracted and interpreted. In this work, we combine principal component analysis (PCA) with readout at relatively low sampling rates to explore the photon-number-resolving capabilities of SNSPDs. We find that the information of the photon number is captured by a single principal component that closely resembles the time derivative of the average response trace. Using the time derivative of the average response trace provides an agnostic method to obtain the photon number from SNSPD traces without the necessity of performing PCA, making this method simple and quick to calibrate. As an auxiliary diagnostic, we use a distinguishability metric based on the Bhattacharyya coefficient [Indian J. Statistics 7, 401 (1946)] to quantify and compare the photon-number-resolving capabilities of different detector systems. Our analysis and interpretation of the principal components imply that photon-number resolution in SNSPDs can be achieved with moderate hardware requirements in terms of both sample rate (5 GS s−1) and analog bandwidth (3 GHz) and could be implemented in a field-programmable gate array, giving a highly scalable solution for real-time photon counting.

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APS Open Sci. 1, 000073– Published 28 July, 2026
Vol. 1
  • Received 17 November 2025
  • Revised 17 March 2026
  • Accepted 26 June 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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