Suppression of back-tunnelling events in hybrid single-electron turnstiles by source-drain bias modulation

TL;DR

This paper introduces a novel bias modulation scheme for hybrid single-electron turnstiles that significantly reduces tunnelling errors, extending high-frequency operation accuracy by an order of magnitude.

Contribution

The authors demonstrate a new AC bias modulation technique with doubled frequency to suppress wrong-direction tunnelling, improving single-electron current accuracy.

Findings

Extended the frequency range for accurate single-electron currents.

Achieved an order of magnitude improvement in current accuracy.

Reduced errors from ~10^{-3} to below 5×10^{-4} at high frequencies.

Abstract

Accuracy of single-electron currents produced in hybrid turnstiles at high operation frequencies is, among other errors, limited by electrons tunnelling in the wrong direction. Increasing the barrier transparency between the island and the leads, and the source-drain bias helps to suppress these events in a larger frequency range, although they lead to some additional errors. We experimentally demonstrate a driving scheme that suppresses tunnelling in the wrong direction hence extending the range of frequencies for generating accurate single-electron currents. The main feature of this approach is an additional AC signal applied to the bias with twice the frequency as the one applied to the gate electrode. This allows additional modulation of the island chemical potential. By using the new approach under certain parameters, we improve the single-electron current accuracy by one order of magnitude. Finally, we show through experimentally-contrasted calculations that our method can improve accuracy even in devices for which the usual gate driving gives errors $\sim 10^{-3}$ at high frequencies and can bring them under $5\times 10^{-4}$.