Strain and Electric Field Control of Hyperfine Interactions for Donor Spin Qubits in Silicon

TL;DR

This paper develops a scalable atomistic tight-binding model to accurately predict how strain and electric fields influence hyperfine interactions in silicon donor qubits, enabling optimized quantum device design.

Contribution

It introduces a comprehensive theoretical framework that captures strain and electric field effects on hyperfine interactions with high accuracy, applicable to realistically sized silicon devices.

Findings

Hybrid strain and electric field control enhances qubit gate fidelity.

Different donor species respond uniquely to strain and fields, affecting hyperfine shifts.

Bi donors benefit from combined in-plane and out-of-plane fields for faster gates.

Abstract

Control of hyperfine interactions is a fundamental requirement for quantum computing architecture schemes based on shallow donors in silicon. However, at present, there is lacking an atomistic approach including critical effects of central-cell corrections and non-static screening of the donor potential capable of describing the hyperfine interaction in the presence of both strain and electric fields in realistically sized devices. We establish and apply a theoretical framework, based on atomistic tight-binding theory, to quantitatively determine the strain and electric field dependent hyperfine couplings of donors. Our method is scalable to millions of atoms, and yet captures the strain effects with an accuracy level of DFT method. Excellent agreement with the available experimental data sets allow reliable investigation of the design space of multi-qubit architectures, based on both strain-only as well as hybrid (strain+field) control of qubits. The benefits of strain are uncovered by demonstrating that a hybrid control of qubits based on (001) compressive strain and in-plane (100 or 010) fields results in higher gate fidelities and/or faster gate operations, for all of the four donor species considered (P, As, Sb, and Bi). The comparison between different donor species in strained environments further highlights the trends of hyperfine shifts, providing predictions where no experimental data exists. Whilst faster gate operations are realisable with in-plane fields for P, As, and Sb donors, only for the Bi donor, our calculations predict faster gate response in the presence of both in-plane and out-of-plane fields, truly benefiting from the proposed planar field control mechanism of the hyperfine interactions.