We report on high-accuracy measurements of quantized current, sourced by a tunable-barrier single-electron pump at frequencies f up to 1 GHz. The measurements were performed with a new picoammeter instrument, traceable to the Josephson and quantum Hall effects. Current quantization according to I=ef with e the elementary charge was confirmed at f=545 MHz with a total relative uncertainty of 0.2 ppm, improving the state of the art by about a factor of 5. For the first time, the accuracy of a possible future quantum current standard based on single-electron transport was experimentally validated to be better than the best realization of the ampere within the present SI.
@article{arxiv.1506.05965,
title = {Validation of a quantized-current source with 0.2 ppm uncertainty},
author = {Friederike Stein and Dietmar Drung and Lukas Fricke and Hansjörg Scherer and Frank Hohls and Christoph Leicht and Martin Götz and Christian Krause and Ralf Behr and Eckart Pesel and Klaus Pierz and Uwe Siegner and Franz-Josef Ahlers and Hans W. Schumacher},
journal= {arXiv preprint arXiv:1506.05965},
year = {2015}
}