Abstract

On-demand transfer of single electrons at sub-nanosecond timescales via semiconductor quantum dots has attracted great interest in the broad context of quantum technologies. While this technique has been initially developed to enable a quantum realization of the unit ampere, more recently it has proved to be key for the emerging field of fermionic quantum optics and it could become instrumental for the upscaling of future solid-state quantum computers.

At present, charge transfers with the lowest uncertainty have been achieved with GaAs quantum dot-based pumps [1]. However, in order to optimally operate these devices, demanding experimental conditions are required, such as very large perpendicular magnetic field, millikelvin temperature, and, in some case, specially tailored waveform of the driving signal [2]. Silicon implementations promise to significantly simplify these operation requirements in light of the mature metal-oxide-semiconductor (MOS) technology offering excellent control of the electrostatic confinement.

In this talk, I will discuss our latest results with silicon MOS quantum dot- based pumps. By improving upon a previous device design [3], we have achieved a tighter electrostatic confinement and charging energies in excess of 30 meV in the few-electron regime. This has resulted in fast and precise single-electron transfers at temperature as high as 4K and frequency in excess of 3.5 GHz by using a single-harmonic driving signal. The robustness of the pumping mechanism is confirmed by the evaluation of random uncertainties below 2 parts per million for variations of the experimental gate voltages of several tens of mV. Finally, I will discuss directions towards the integration of superconductor charge sensors and silicon pumps for charge counting experiments [4], as well as the realization of ambipolar devices to compare and contrast pumping with electrons and holes.

[1] F. Stein et al., Appl. Phys. Lett. 107, 103501 (2015). [2] S.P. Giblin et al., Nature Comm. 3, 930 (2012). [3] A. Rossi et al., Nano Lett. 14, 3405 (2014). [4] T. Tanttu et al. New J. Phys. 17, 103030 (2015).