Molecular Engineering of antiferromagnetic rings for quantum computation.

The substitution of one metal ion in a Cr-based molecular ring with dominant antiferromagneticcouplings allows the engineering of its level structure and ground-state degeneracy. Here we characterize aCr7Ni molecular ring by means of low-temperature specific-heat and torque-magnetometry measurements,thus determining the microscopic parameters of the corresponding spin Hamiltonian. The energyspectrum and the suppression of the leakage-inducing S mixing render the Cr7Ni molecule a suitablecandidate for the qubit implementation, as further substantiated by our quantum-gate simulations.