An important step in this direction seems to have been made
by a quantum computing company using superconducting flux
qubits [38].
We investigated the possibility to implement a two-qubit
quantum CNOT gate that uses the electron spins carried by the
vacancy-nitrogen defect of diamond and a nearby nitrogen atom in
substitutional position. This is a new approach. It is the hyperfine
interaction which is usually considered. The manipulation of spins
is realized by irradiation of the spin system with a two-pulse
sequence. The free parameters involved in Eqs. (4)–(8) offer other
possibilities that can be explored.