Demonstration of single-flux-quantum readout operation for superconducting single-photon detectors

TLDR

A superconducting single‑flux‑quantum readout circuit was developed to enable an independently addressable array of superconducting single‑photon detectors. The circuit was tested by coupling it to SSPDs, measuring detection efficiencies with and without the readout, and observing that the efficiency curves were essentially unchanged except for a tendency to latch when the readout was connected. The readout achieved error rates below 10⁻⁵ for input amplitudes above 18.2 µA, and while detection efficiencies remained comparable, the SSPD was prone to latch when the readout was connected.

Abstract

A readout circuit using superconducting single-flux-quantum (SFQ) circuits has been developed to realize an independently addressable array of superconducting single-photon detectors (SSPDs). We tested the SFQ readout circuits by connecting with SSPDs. The error rates of readout circuits were below 10−5 for input signal amplitude of greater than 18.2 μA. Detection efficiencies (DEs) for single-photon incidents were measured both with and without the connection of a readout circuit. The observed DEs traced almost the same curves regardless of the connection of the readout circuit, except that the SSPD is likely to latch by connecting the readout circuit.