We propose a scalable design for a solid-state spin-based quantum computer. It uses endohedral fullerenes like $\mathrm{N}@{\mathrm{C}}_{60}$ or $\mathrm{P}@{\mathrm{C}}_{60},$ 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.

• Received 22 November 2001

DOI:https://doi.org/10.1103/PhysRevA.65.052309