Full configuration interaction simulations of exchange-coupled donors in silicon using multi-valley effective mass theory

TL;DR

This paper models the exchange interaction between donor electrons in silicon using a full configuration interaction approach within a multi-valley effective mass framework, aiding the design of high-fidelity quantum gates.

Contribution

It introduces a computationally efficient method to simulate two-electron wave functions in silicon donors, providing detailed insights into exchange interactions and valley populations for quantum computing.

Findings

Exchange interaction varies with donor placement and electric fields.

Valley populations are sensitive to donor positions and orientations.

The method enables visualization of wave function evolution in different configurations.

Abstract

Donor spin in silicon have achieved record values of coherence times and single-qubit gate fidelities. The next stage of development involves demonstrating high-fidelity two-qubit logic gates, where the most natural coupling is the exchange interaction. To aid the efficient design of scalable donor-based quantum processors, we model the two-electron wave function using a full configuration interaction method within a multi-valley effective mass theory. We exploit the high computational efficiency of our code to investigate the exchange interaction, valley population, and electron densities for two phosphorus donors in a wide range of lattice positions, orientations, and as a function of applied electric fields. The outcomes are visualized with interactive images where donor positions can be swept while watching the valley and orbital components evolve accordingly. Our results provide a physically intuitive and quantitatively accurate understanding of the placement and tuning criteria necessary to achieve high-fidelity two-qubit gates with donors in silicon.