  Recent advances in silicon nanofabrication have allowed the manipulation of
spin qubits that are extremely isolated from noise sources, being therefore the
semiconductor equivalent of single atoms in vacuum. We investigate the
possibility of directly coupling an electron spin qubit to a superconducting
resonator magnetic vacuum field. By using resonators modified to increase the
vacuum magnetic field at the qubit location, and isotopically purified 28Si
substrates, it is possible to achieve coupling rates faster than the single
spin dephasing. This opens up new avenues for circuit-quantum electrodynamics
with spins, and provides a pathway for dispersive read-out of spin qubits via
superconducting resonators.
