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.
@article{arxiv.1610.03994,
title = {Three addressable spin qubits in a molecular single-ion magnet},
author = {Mark David Jenkins and Yan Duan and Beatriz Diosdado and Juan José García-Ripoll and Alejandro Gaita-Ariño and Carlos Giménez-Saíz and Pablo J. Alonso and Eugenio Coronado and Fernando Luis},
journal= {arXiv preprint arXiv:1610.03994},
year = {2017}
}