Detection of ultra-weak laser pulses by free-running single-photon detectors: Modeling dead time and dark counts effects

Hristina Georgieva,Marco Genovese,Marco Gramegna,Helmuth Hofer,Alice Meda,Marco López,Ivo Pietro Degiovanni,Stefan Kück,Sebastian M F Raupach

doi:10.1063/5.0046014

Abstract

In quantum communication systems, the precise estimation of the detector´s response to the incoming light is necessary to avoid security breaches. The typical working regime uses a free-running single-photon avalanche diode in combination with attenuated laser pulses at telecom wavelength for encoding information. We demonstrate the validity of an analytical model for this regime that considers the effects of dark counts and dead time on the measured count rate. For the purpose of gaining a better understanding of these effects, the photon detections were separated from the dark counts via a software-induced gating mechanism. The model was verified by experimental data for mean photon numbers covering three orders of magnitude as well as for laser repetition frequencies below and above the inverse dead time. Consequently, our model would be of interest for predicting the detector response not only in the field of quantum communications, but also in any other quantum physics experiment where high detection rates are needed.

Highlights

As already stated, the detectors are generally considered the most vulnerable part,[18–32] so to guarantee security and avoid tailored attacks, the response of a SPAD to the incoming light in different regimes needs to be modeled and tested, taking into account its characteristic parameters and a regime of operation as broad as possible
We demonstrate the validity of an analytical model for this regime that considers the effects of dark counts and dead time on the measured count rate
Our model would be of interest for predicting the detector response in the field of quantum communications, and in any other quantum physics experiment where high detection rates are needed

Summary

Introduction

The detectors are generally considered the most vulnerable part,[18–32] so to guarantee security and avoid tailored attacks, the response of a SPAD to the incoming light in different regimes needs to be modeled and tested, taking into account its characteristic parameters (mainly quantum efficiency, dead time and dark counts) and a regime of operation as broad as possible. The model was verified by experimental data for mean photon numbers covering three orders of magnitude as well as for laser repetition frequencies below and above the inverse dead time.

Results

Conclusion