Long hold times in a two-junction electron trap

TL;DR

This paper demonstrates that enhanced electromagnetic shielding can significantly increase the hold time of a two-junction electron trap, reaching up to 10 hours, by suppressing environmentally assisted tunneling events.

Contribution

The study shows that using two rf-tight shields instead of one greatly extends the trap's hold time, highlighting the importance of environmental isolation in electron trapping.

Findings

Hold time increased by over 1000 times with improved shielding.

Achieved up to 10 hours of trap stability.

Normal state hold time around 100 seconds aligns with quantum leakage predictions.

Abstract

The hold time $\tau$ of a single-electron trap is shown to increase significantly due to suppression of environmentally assisted tunneling events. Using two rf-tight radiation shields instead of a single one, we demonstrate increase of $\tau$ by a factor exceeding $10^3$, up to about 10 hours, for a trap with only two superconductor (S) -- normal-metal (N) tunnel junctions and an on-chip resistor $R$ (R-SNS structure). In the normal state, the improved shielding made it possible to observe $\tau\sim$ 100 s, which is in reasonable agreement with the quantum-leakage-limited level expected for the two-electron cotunneling process.