The dynamic quantum dot as an accurate electron pump

We have developed an accurate single electron pump based on a dynamic quantum dot realised in a GaAs two-dimensional electron system. We report an accurate comparison between the pump current and a reference current derived from quantum standards of voltage and resistance: the Josephson effect and quantum Hall effect. We find that, at a clock frequency of several hundred Megahertz, the pump can transfer one electron per clock cycle with an accuracy approaching 10 parts per million. We discuss the significance of this result in relation to the proposed re- definition of the SI base unit Ampere. Theoretical estimations of the pump error rate indicate that an accuracy of one part in a hundred million is attainable, making our type of pump a candidate for a metrological current standard.