A new accuracy record in measurements on single-electron pumps has been demonstrated by PTB. 0.16 µA/A of relative combined uncertainty was reached within less than 1 day of measurement time. Robustness tests of pump operation on the sub-ppm level revealed good stability of tunable-barrier pumps against variations in the operating parameters.

Electron micrographs of electron pumps and potential energy diagram showing pump operation.

Single-electron (SE) pumps are promising candidates for future quantum current standards. Use in future metrological applications demands higher current level (at least 100 pA) and sufficiently wide margins of their operating parameters. For practical applications the accuracy of the sourced current has to be invariant (‘robust’) with regard to variations of relevant driving parameters within certain margins.

PTB has investigated SE pumps made from GaAs-based heterostructures under systematic variations of operational parameters such as magnetic flux density, bias and gate voltages, and pump driving frequency.

Improvements in the small-current measurement technique based on the ultrastable low-noise current amplifier enabled a new accuracy record in current generation with an SE pump to be achieved (0.16 µA/A at a current of about 100 pA). They also showed that SE pumps of tunable-barrier type can provide robust high-accuracy current generation within reasonably wide ranges of their operational parameters.

This work was published open-access in Metrologia, a journal of the Institute of Physics (IOP):

“Robustness of single-electron pumps at sub-ppm current accuracy level”, Metrologia 54, S1–S8 (2017);

F. Stein, H. Scherer, T. Gerster, R. Behr, M. Götz, E. Pesel, C. Leicht, N. Ubbelohde, T. Weimann, K. Pierz, H. W. Schumacher, and F. Hohls,