Characterization of Josephson Junction Aging and Annealing Under Different Environments

TL;DR

This study investigates how Josephson junctions age under various storage conditions and how annealing affects their resistance, providing insights for improving superconducting quantum processor reliability.

Contribution

It characterizes the aging behavior of Josephson junctions over months and compares the effects of different annealing environments on their resistance.

Findings

Aging follows a logarithmic curve influenced by fabrication and storage conditions.

Junctions stored in nitrogen or vacuum age slower than those stored in ambient conditions.

Annealing in nitrogen decreases resistance across tested temperatures, while ambient annealing shows mixed effects.

Abstract

Understanding the aging behavior of Josephson junctions and the effect of annealing on junction resistances is important in building large-scale superconducting quantum processors. Here we study the effects of aging of Josephson junctions under different storage conditions from immediately after fabrication up to 2 to 3 months. We find that the aging curve follows a logarithmic curve, with the aging amplitude mainly determined by fabrication conditions and the aging speed determined by storage conditions. Junctions stored at ambient laboratory conditions aged faster compared to junctions stored in a nitrogen atmosphere or vacuum, with the aging speed appreciably changes when the storage condition changed. We also compared the effect of thermal annealing under nitrogen environment with annealing under ambient conditions up to 250$^\circ$ C. We find that under nitrogen environment, the resistances decreased at all temperatures tested, while under ambient environment the resistances increased at 200$^\circ$ C and decreased at 250$^\circ$ C instead. We were unable to decrease the resistance below the initial-time resistance, suggesting a lower limit on the range of resistance tuning.