Scalable architecture for spin-based quantum computers with a single type of gate

We propose a scalable design for a solid-state spin-based quantum computer. It uses endohedral fullerenes like N@C-60 or P@C-60, which can be positioned on Si surfaces with a scanning tunneling microscope. Each logical qubit is stored in two physical qubits, corresponding to the nuclear and electronic spins. We discuss the addressing of individual qubits by a magnetic field gradient, and the implementation of one- and two-qubit quantum gates by sequences of radio-frequency and microwave pulses.