Quantum control of donor-bound electrons at the Si-SiO₂ interface

Prospects for the quantum control of electrons in the silicon quantum computer architecture are considered theoretically. We focus here on the ability to move or "shuttle" electrons between the donors and the Si surface using an external electric field. This is an essential element of donor-based quantum computer architectures. In particular, this shuttling time must be much shorter than the spin dephasing time ∼ 1 ms in bulk Si. Application of suitable electrostatic potentials at surface electrodes would drag the electron from and to the donor allowing the manipulation of the electron-donor coupling. We investigate the precise extent to which a donor bound electron in the bulk (a few tens of nanometers from the interface) can be manipulated between the donor-bound state and a surface-bound state (within a few nanometers of the interface) by suitably tuning an external electric field applied perpendicular to the interface.