Three-waveform bidirectional pumping of single electrons with a silicon   quantum dot
  Semiconductor-based quantum dot single-electron pumps are currently the most promising candidates for the direct realization of the emerging quantum standard of the ampere in the International System of Units. Here, we discuss a silicon quantum dot single-electron pump with radio frequency control over the transparencies of entrance and exit barriers as well as the dot potential. We show that our driving protocol leads to robust bidirectional pumping: one can conveniently reverse the direction of the quantized current by changing only the phase shift of one driving waveform with respect to the others. We also study the improvement in the robustness of the current quantization owing to the introduction of three control voltages in comparison with the two-waveform driving. We anticipate that this pumping technique may be used in the future to perform error counting experiments by pumping the electrons into and out of a reservoir island monitored by a charge sensor. 
Tuomo Tanttu, Alessandro Rossi, Kuan Yen Tan, Akseli M\"akinen, Kok   Wai Chan, Andrew S. Dzurak, Mikko M\"ott\"onen
cond-mat.mes-hall cond-mat.other