Controlling the error mechanism in a tunable-barrier non-adiabatic charge pump by dynamic gate compensation

TL;DR

This paper demonstrates control over transfer errors in a tunable-barrier quantum dot charge pump by using dynamic gate compensation, confirming the decay cascade model and enabling error suppression for quantum current standards.

Contribution

It introduces a two-gate operation scheme to verify and control backtunneling errors, confirming the decay cascade model and enabling error suppression in quantum dot pumps.

Findings

Verification of the decay cascade model predictions.

Controlled transition between backtunneling and thermal error regimes.

Error suppression by several orders of magnitude at zero magnetic field.

Abstract

Single-electron pumps based on tunable-barrier quantum dots are the most promising candidates for a direct realization of the unit ampere in the recently revised SI: they are simple to operate and show high precision at high operation frequencies. The current understanding of the residual transfer errors at low temperature is based on the evaluation of backtunneling effects in the decay cascade model. This model predicts a strong dependence on the ratio of the time dependent changes in the quantum dot energy and the tunneling barrier transparency. Here we employ a two-gate operation scheme to verify this prediction and to demonstrate control of the backtunneling error. We derive and experimentally verify a quantitative prediction for the error suppression, thereby confirming the basic assumptions of the backtunneling (decay cascade) model. Furthermore, we demonstrate a controlled transition from the backtunneling dominated regime into the thermal (sudden decoupling) error regime. The suppression of transfer errors by several orders of magnitude at zero magnetic field was additionally verified by a sub-ppm precision measurement.