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

Accuracy of single-electron currents produced in hybrid single-electron turnstiles at high operation frequencies is, among other errors, limited by electrons tunnelling in the wrong direction. Increasing both 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 source-drain bias allowing additional modulation of the island chemical potential and control of the time-window for desired tunnelling events. By using this 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 $5\times 10^{-4}$.Comment: 8 pages + 5 pages supplementary materia