Multielectron dots provide faster Rabi oscillations when the core electrons are strongly confined

TL;DR

This study investigates how the confinement potential's anharmonicity influences Rabi oscillation speeds in multielectron silicon quantum dots, revealing that engineered confinement can optimize qubit gate speeds.

Contribution

It provides a detailed quantitative analysis of how anharmonic confinement affects Rabi frequencies in multielectron quantum dots, guiding qubit design improvements.

Findings

Anharmonicity significantly impacts Rabi frequencies.

Double dots enable fast Rabi oscillations.

Engineered confinements can achieve high Rabi speeds in single dots.

Abstract

Increasing the number of electrons in electrostatically confined quantum dots can enable faster qubit gates. Although this has been experimentally demonstrated, a detailed quantitative understanding has been missing. Here we study one- and three-electron quantum dots in silicon/silicon-germanium heterostructures within the context of electrically-driven spin resonance (EDSR) using full configuration interaction and tight binding approaches. Our calculations show that anharmonicity of the confinement potential plays an important role: while the EDSR Rabi frequency of electrons in a harmonic potential is indifferent to the electron number, soft anharmonic confinements lead to larger and hard anharmonic confinements lead to smaller Rabi frequencies. We also confirm that double dots allow fast Rabi oscillations, and further suggest that purposefully engineered confinements can also yield similarly fast Rabi oscillations in a single dot. Finally, we discuss the role of interface steps. These findings have important implications for the design of multielectron Si/SiGe quantum dot qubits.