Effects of J-gate potential and interfaces on donor exchange coupling in the Kane quantum computer architecture

TL;DR

This paper investigates how J-gate potential and silicon interface effects influence electron exchange and hyperfine interactions in phosphorus donors, providing insights for optimizing qubit operations in Kane quantum computers.

Contribution

It offers a detailed calculation of exchange and hyperfine interactions considering device geometry and gate voltage, advancing understanding of donor-based quantum computing.

Findings

Exchange coupling varies with donor separation and gate voltage.

Hyperfine interaction depends on donor depth and device conditions.

Results inform experimental design for quantum device optimization.

Abstract

We calculate the electron exchange coupling for a phosphorus donor pair in silicon perturbed by a J-gate potential and the boundary effects of the silicon host geometry. In addition to the electron-electron exchange interaction we also calculate the contact hyperfine interaction between the donor nucleus and electron as a function of the varying experimental conditions. Donor separation, depth of the P nuclei below the silicon oxide layer and J-gate voltage become decisive factors in determining the strength of both the exchange coupling and the hyperfine interaction - both crucial components for qubit operations in the Kane quantum computer. These calculations were performed using an anisotropic effective-mass Hamiltonian approach. The behaviour of the donor exchange coupling as a function of the device parameters varied provides relevant information for the experimental design of these devices.