Readout of superconducting nanowire single-photon detectors at high count rates

TL;DR

This paper investigates the limitations of conventional electrical readout in superconducting nanowire single-photon detectors, identifies nonlinear effects that hinder high-rate operation, and proposes an improved readout method enabling stable high-rate detection.

Contribution

It reveals the nonlinear interaction in traditional readout schemes and introduces an improved method that allows stable high-rate operation of SNSPDs.

Findings

Conventional readout causes nonlinear effects limiting high-rate operation.

Experimental confirmation of readout-induced nonlinearities.

Proposed readout improves high-rate stability with minimal efficiency loss.

Abstract

Superconducting nanowire single-photon detectors are set apart from other photon counting technologies above all else by their extremely high speed, with few-ten-ps timing resolution, and recovery times $\tau_R\lesssim$10 ns after a detection event. In this work, however, we identify in the conventional electrical readout scheme a nonlinear interaction between the detector and its readout which can make stable, high-efficiency operation impossible at count rates even an order-of-magnitude less than $\tau_R^{-1}$. We present detailed experimental confirmation of this, and a theoretical model which quantitatively explains our observations. Finally, we describe an improved readout which circumvents this problem, allowing these detectors to be operated stably at high count rates, with a detection efficiency penalty determined purely by their inductive reset time.