Optimal spin-qubit hallmarks of sulfur-vacancy defects in 4H-SiC: Design from first principles

TL;DR

This paper proposes a sulfur-vacancy defect in 4H-SiC as a promising optically controllable spin qubit with stable triplet ground state and high coherence potential, based on first-principles calculations.

Contribution

It introduces a new defect design in 4H-SiC with favorable spin and optical properties for quantum computing applications, confirmed through advanced computational methods.

Findings

Defect has a stable triplet ground state suitable for qubits.

Electronic states form sharp peaks within the band gap.

Defect exhibits intense near-infrared optical excitations.

Abstract

By applying our methodology, we propose a defect in 4H-SiC which combines a Si vacancy and a C atom substituted with S (VSiSC) to have a spin-triplet ground state with the spin qubit functionality. Our calculations confirm that all configurations of the defect have a dynamically and thermodynamically stable triplet ground state and higher energy singlet states, essential for the spin-qubit polarization cycle. From GW calculations, we found that the electronic states associated with the defect form sharp and isolated peaks within the band gap for both triplet and singlet states. Further Bethe-Salpeter-equation calculations show that all considered configurations have intense optical excitations in the near infrared spectrum range. Analysis of the excitation energies and rates indicate that the VSiSC defect can be an excellent optically controlled spin qubit. Crucially, the host elements and the dopant have high-abundance isotopes with zero nuclear spin ensuring high spin-coherence time of the qubit.