Low frequency resistance and critical current fluctuations in Al-based Josephson junctions

TL;DR

This study investigates low-frequency 1/f noise in Al/AlO$_{x}$/Al Josephson junctions, revealing that noise scales linearly with temperature and is linked to two-level fluctuators, impacting qubit performance.

Contribution

The paper provides a detailed analysis of 1/f noise in Al-based Josephson junctions, establishing the temperature and area dependence and connecting noise sources to glassy two-level fluctuators.

Findings

Noise power spectrum scales linearly with temperature.

Density of two-level fluctuators similar to glassy systems.

Critical current and resistance noise are equivalent.

Abstract

We present low-temperature measurements of the low-frequency $1/f$ noise arising from an ensemble of two-level fluctuators in the oxide barrier of Al/AlO$_{x}$/Al Josephson junctions. The fractional noise power spectrum of the critical-current and normal-state resistance have similar magnitudes and scale linearly with temperature, implying an equivalence between the two. Compiling our results and published data, we deduce the area and temperature scaling of the noise for AlO$_{x}$ barrier junctions. We find that the density of two-level fluctuators in the junction barrier is similar to the typical value in glassy systems. We discuss the implications and consistency with recent qubit experiments.