Effects of J-gate potential and uniform electric field on a coupled donor pair in Si for quantum computing

We present theoretical studies of a coupled-donor pair in Si via an unrestricted Hartree-Fock method with a generalized valence bond wave function. Polarization properties and exchange coupling for a phosphorous donor pair in silicon under a J-gate potential (modeled by a parabolic well) and a uniform electric field (either parallel or perpendicular to the interdonor axis) are examined. The energies and charge distributions of the lowest-lying singlet and triplet states as functions of the J-gate potential and uniform electric field for various donor separations are analyzed. Implications for Si:P electron-spin-based quantum computer architecture are discussed.