All-electrical manipulation of silicon spin qubits with tunable spin-valley mixing

TL;DR

This paper demonstrates how electric fields can control spin-valley mixing in silicon qubits, enabling switchable modes for robust and scalable quantum information processing, with simulations showing practical device implementations.

Contribution

It introduces a method to electrically tune spin-valley mixing in silicon qubits, enabling mode switching for improved qubit control and robustness.

Findings

Electric field controls spin-valley mixing via valley splitting.

Qubit can switch between spin and valley modes electrically.

Simulations show practical device configurations for this control.

Abstract

We show that the mixing between spin and valley degrees of freedom in a silicon quantum bit (qubit) can be controlled by a static electric field acting on the valley splitting $\Delta$. Thanks to spin-orbit coupling, the qubit can be continuously switched between a spin mode (where the quantum information is encoded into the spin) and a valley mode (where the the quantum information is encoded into the valley). In the spin mode, the qubit is more robust with respect to inelastic relaxation and decoherence, but is hardly addressable electrically. It can however be brought into the valley mode then back to the spin mode for electrical manipulation. This opens new perspectives for the development of robust and scalable, electrically addressable spin qubits on silicon. We illustrate this with tight-binding simulations on a so-called "corner dot" in a silicon-on-insulator device where the confinement and valley splitting can be independently tailored by a front and a back gate.