Switchable Interaction in Molecular Double Qubits

Quantum information processing (QIP) could revolutionize how we simulate and understand quantum systems. Any QIP scheme requires both individual units (qubits) that have long phase memories and switchable units that can be placed between the qubits. Here, we describe supramolecular systems where {Cr7Ni} rings are used as qubits, linked by redox-switchable {Ru2M} oxo-centered triangles (M = Zn, Ni, or Co). The supramolecular assemblies have been structurally characterized and involve two {Cr7Ni} rings bound to {Ru2M} triangles through iso-nicotinate ligands. Detailed physical studies, including electrochemistry and electron paramagnetic resonance spectroscopy, show that when M = Co, the supramolecular assembly has the physical characteristics needed to implement the √iSWAP gate, which is an important entangling two-qubit gate. Detailed simulations show that the fidelity of this gate is potentially very high and depends on the phase memory time of the {Cr7Ni} qubits but not the {Ru2Co} switch