Photocounting statistics of superconducting nanowire single-photon detectors

TL;DR

This paper develops a theoretical model for superconducting nanowire single-photon detectors (SNSPDs), incorporating their dead time and memory effects, and analyzes how these factors influence photocounting statistics in continuous-wave detection.

Contribution

It introduces a new photocounting formula for SNSPDs that accounts for dead time and memory effects, enhancing understanding of their detection statistics.

Findings

Memory effects significantly alter photocounting statistics.

Relaxation processes impact detection efficiency.

Nonlinear dependence on the density operator is demonstrated.

Abstract

Superconducting nanowire single-photon detectors (SNSPDs) are efficient measurement devices used for counting single photons. The field of their applications covers experimental quantum-optical studies, optical quantum computing, quantum communication, and others. After registering a photon by such a detector, the next one cannot be registered during the dead time and after that this ability is smoothly restored. We have included this feature into the photodetection theory and introduced the corresponding photocounting formula. In the regime of continuous-wave detection, the photocounting statistics nonlinearly depends on the density operator due to a memory effect of previous measurement time windows. The considered examples demonstrate the strong influence of the relaxation process and the memory effect on the resulting photocounting statistics of the SNSPDs.