Experimental determination of the elastic cotunneling rate in a hybrid single-electron box

TL;DR

This study measures charge transfer dynamics in a hybrid aluminum-copper single-electron box, focusing on elastic cotunneling rates, which are crucial for understanding errors in hybrid electron turnstiles.

Contribution

The paper provides experimental measurements of elastic cotunneling rates in a hybrid single-electron box, confirming theoretical estimates and highlighting their significance in device accuracy.

Findings

Elastic cotunneling rate as low as 1 Hz at degeneracy

Charge configurations mapped using two SETs

Results align with theoretical tunneling estimates

Abstract

We report measurements of charge configurations and charge transfer dynamics in a hybrid single-electron box composed of aluminum and copper. We used two single-electron transistors (SETs) to simultaneously read out different parts of the box, enabling us to map out stability diagrams of the box and identify various charge transfer processes in the box. We further characterized the elastic cotunneling in the box, which is an important source of error in electron turnstiles consisting of hybrid SETs, and found that the rate was as low as 1 Hz at degeneracy and compatible with theoretical estimates for electron tunneling via virtual states in the central superconducting island of the box.