Engineering hyperfine Stark shifts for addressable high-speed gates in donor molecules in silicon*

Electron and nuclear spin qubits on single donor atoms in silicon have demonstrated long coherence times with high fidelities. Recent results have demonstrated the ability to form fast (0.8ns) two qubit gates using donor molecules in silicon. Scalable quantum computer architectures require the ability to combine fast single and two qubit gates with individual qubit addressability across an array to minimise errors on neighbouring qubits. Single donor qubits require a large ~30MHz/MVm^-1 hyperfine Stark shift of the qubit resonance frequency to uniquely address identical single donor nuclear spins. Previous results on single phosphorus donor spins have measured a hyperfine Stark coefficient of 0.34MHz/MVm^-1, well below that identified in the Kane architecture thereby limiting the speed of addressable quantum gates. By comparing experimental results of donor molecules in silicon with tight binding simulations of 2P molecules we demonstrate atomic engineering of donor qubits in silicon to control a large range of hyperfine Stark coefficients (up to 72MHz/MVm^-1). We discuss how these results can be extended to achieving high speed gates using electrically driven spin resonance control.