External field control of donor electron exchange at the Si/SiO2 interface

TL;DR

This paper investigates how external electric and magnetic fields can control donor electron states and exchange interactions at the Si/SiO2 interface, crucial for silicon-based quantum computing, providing conditions for qubit operations and potential experimental pathways.

Contribution

It introduces a detailed analysis of donor-bound electron manipulation and exchange coupling control at the Si/SiO2 interface, highlighting conditions for qubit operations without local gates and estimating feasible donor densities.

Findings

Donor-bound electron states can be manipulated by electric and magnetic fields.

Conditions to maintain donor-bound states at the interface are established.

Exchange coupling at the interface can be comparable to GaAs quantum dots, enabling similar quantum control experiments.

Abstract

We analyze several important issues for the single- and two-qubit operations in Si quantum computer architectures involving P donors close to a SiO2 interface. For a single donor, we investigate the donor-bound electron manipulation (i.e. 1-qubit operation) between the donor and the interface by electric and magnetic fields. We establish conditions to keep a donor-bound state at the interface in the absence of local surface gates, and estimate the maximum planar density of donors allowed to avoid the formation of a 2-dimensional electron gas at the interface. We also calculate the times involved in single electron shuttling between the donor and the interface. For a donor pair, we find that under certain conditions the exchange coupling (i.e. 2-qubit operation) between the respective electron pair at the interface may be of the same order of magnitude as the coupling in GaAs-based two-electron double quantum dots where coherent spin manipulation and control has been recently demonstrated (for example for donors ~10 nm below the interface and \~40 nm apart, J~10^{-4} meV), opening the perspective for similar experiments to be performed in Si.