An adiabatic superconductor comparator with 46 nA sensitivity

TL;DR

This paper introduces a high-sensitivity AQFP comparator with a current transformer, achieving 46 nA sensitivity at 4.2 K, enhancing cryogenic detector readout capabilities.

Contribution

The study presents a novel AQFP comparator with a current transformer that significantly improves sensitivity compared to conventional designs.

Findings

Achieved 46 nA sensitivity at 4.2 K

Numerical simulation shows sixfold sensitivity improvement

Demonstrated effective operation at 500 Hz sampling frequency

Abstract

Adiabatic quantum-flux-parametron (AQFP) circuits can operate with extremely small energy dissipation (~1 zJ per junction at 5 GHz) and high sensitivity (~1 {\mu}A) owing to adiabatic switching. Thus, AQFP logic is suitable to use as readout interfaces for cryogenic detectors, such as superconducting nanowire single-photon detectors (SSPDs). In order to extend the application of AQFP logic to various detectors, it is crucial to achieve even better sensitivity because some detectors, such as WSi SSPDs and transition edge sensors (TESs), require sub-{\mu}A sensitivity. In the present study, we propose a high-sensitivity AQFP comparator with a current transformer (CT), which increases the equivalent input current and thereby improves the sensitivity. Numerical simulation shows that the proposed comparator achieves a sensitivity approximately six times better than that of a conventional AQFP comparator. Furthermore, we demonstrate a sensitivity of 46 nA at 4.2 K for a sampling frequency of 500 Hz in the experiment.