Figure 1.

Some selected examples of electron spin based systems of interest as potential qubits because of their long spin coherence times: defects in diamonds constituted by nitrogen-vacancy pairs (a), vacancies in silicon carbide (b), coordination compounds of metal ions carrying unpaired electrons (c). The [V(C₈S₈)₃]^2– complex with nuclear-free ligands discussed in ref (4) is represented here. The manipulation of a spin qubit can be performed by the pulsed EPR technique, and the system can be prepared in any arbitrary superposition of the spin-up and spin-down states through a nutation experiment schematized in (d).