  We show that several qubits can be integrated in a single magnetic ion, using
its internal electronic spin states with energies tuned by a suitably chosen
molecular environment. This approach is illustrated with a nearly-isotropic
Gd(III) ion entrapped in a polyoxometalate molecule. Experiments with microwave
technologies, either three dimensional cavities or quantum superconducting
circuits, show that this magnetic molecule possesses the number of spin states
and the set of coherently addressable transitions connecting these states that
are needed to perform a universal three-qubit processor or, equivalently, a
d=8-level 'qudit'. Our findings open prospects for developing more
sophisticated magnetic molecules which can result in more powerful and noise
resilient quantum computation schemes.
