Universality and Multiplication of Gigahertz-Operated Silicon Pumps with Parts Per Million-Level Uncertainty

The universality of physical phenomena is a pivotal concept underlying quantum standards. In this context, the realization of a quantum current standard using silicon single-electron pumps necessitates the verification of the equivalence across multiple devices. Herein, we experimentally investigate the universality of pumped currents from two different silicon single-electron devices which are placed inside the cryogen-free dilution refrigerator whose temperature (mixing chamber plate) was ∼150 mK under the operation of the pump devices. By direct comparison using an ultrastable current amplifier as a galvanometer, we confirm that two pumped currents are consistent with ∼1 ppm uncertainty. Furthermore, we realize quantum-current multiplication with a similar uncertainty by adding the currents of two different gigahertz (GHz)-operated silicon pumps, whose generated currents are confirmed to be identical. These results pave the way for realizing a quantum current standard in the nanoampere range and a quantum metrology triangle experiment using silicon pump devices.

Gigahertz Single-Electron Pumping Mediated by Parasitic States

In quantum metrology, semiconductor single-electron pumps are used to generate accurate electric currents with the ultimate goal of implementing the emerging quantum standard of the ampere. Pumps based on electrostatically defined tunable quantum dots (QDs) have thus far shown the most promising performance in combining fast and accurate charge transfer. However, at frequencies exceeding approximately 1 GHz the accuracy typically decreases. Recently, hybrid pumps based on QDs coupled to trap states have led to increased transfer rates due to tighter electrostatic confinement. Here, we operate a hybrid electron pump in silicon obtained by coupling a QD to multiple parasitic states and achieve robust current quantization up to a few gigahertz. We show that the fidelity of the electron capture depends on the sequence in which the parasitic states become available for loading, resulting in distinctive frequency-dependent features in the pumped current.