An electrically driven spin qubit based on valley mixing
  The electrical control of single spin qubits based on semiconductor quantum dots is of great interest for scalable quantum computing since electric fields provide an alternative mechanism for qubit control compared with magnetic fields and can also be easier to produce. Here we outline the mechanism for a drastic enhancement in the electrically-driven spin rotation frequency for silicon quantum dot qubits in the presence of a step at a hetero-interface. The enhancement is due to the strong coupling between the ground and excited states which occurs when the electron wave-function overcomes the potential barrier induced by the interface step. We theoretically calculate single qubit gate times of 170ns for a quantum dot confined at a silicon/silicon-dioxide interface. The engineering of such steps could be used to achieve fast electrical rotation and entanglement of spin qubits despite the weak spin-orbit coupling in silicon. 
Wister Huang, Menno Veldhorst, Neil M. Zimmerman, Andrew S. Dzurak and   Dimitrie Culcer
cond-mat.mes-hall