Valley Phase and Voltage Control of Coherent Manipulation in Si Quantum Dots

TL;DR

This paper presents an analytical method to calculate and control the valley-orbit phase in silicon quantum dots, enabling precise manipulation of exchange splitting and qubit frequencies through gate voltages.

Contribution

It introduces a simple analytical approach to determine valley phase and demonstrates how lateral gate control can tune this phase in silicon quantum dots.

Findings

Analytical calculation of valley-orbit phase for arbitrary interfaces

Demonstration of gate voltage control over valley phase

Potential for precise exchange splitting control in quantum devices

Abstract

With any roughness at the interface of an indirect-bandgap semiconducting dot, the phase of the valley-orbit coupling can take on a random value. This random value, in double quantum dots, causes a large change in the exchange splitting. We demonstrate a simple analytical method to calculate the phase, and thus the exchange splitting and singlet-triplet qubit frequency, for an arbitrary interface. We then show that, with lateral control of the position of a quantum dot using a gate voltage, the valley-orbit phase can be controlled over a wide range, so that variations in the exchange splitting can be controlled for individual devices. Finally, we suggest experiments to measure the valley phase and the concomitant gate voltage control.