Continuous Real-Time Detection of Quasiparticle Trapping in Aluminum Nanobridge Josephson Junctions

TL;DR

This paper presents a real-time detector for quasiparticle trapping in aluminum nanobridge Josephson junctions, enabling continuous monitoring of quasiparticles with high sensitivity and potential for optimization in superconducting electronics.

Contribution

The study introduces a novel continuous quasiparticle trapping detector based on a two-junction aluminum nanobridge SQUID integrated into a resonator, demonstrating high sensitivity and real-time detection capabilities.

Findings

Detected up to 3 trapped quasiparticles simultaneously

Achieved a signal-to-noise ratio of 27 in 5 microseconds

Provided initial insights into quasiparticle behavior in superconducting junctions

Abstract

Nonequilibrium quasiparticles are ubiquitous in superconducting electronics. These quasiparticles can trap in the internal Andreev bound states of a phase-biased Josephson junction, providing a mechanism for studying their presence and behavior. We characterize a quasiparticle trapping detector device based on a two-junction aluminum nanobridge superconducting quantum interference device incorporated into a transmission-line resonator. When flux-biased, distinct resonant frequencies develop depending on the trapped quasiparticle number. We demonstrate continuous detection of up to 3 trapped quasiparticles, with detection of a trapped quasiparticle with signal-to-noise ratio of 27 in 5 $\mu$s. We describe initial measurements of quasiparticle behavior and discuss the possible optimization and application of such detector devices.