Scaling Up quantum computation with Molecular spins

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SUQMO aims to set the basis of a new architecture for quantum computation and simulation, in which information is encoded in spin qubits trapped in molecules that are read-out and communicate via their coupling to a superconducting resonator. This technology has a high potential for robustness and scalability, based on the microscopic and perfectly reproducible nature of the molecular building blocks and on the possibility of embodying multiple qubits in each of them, which provide an extra dimension to increase computational resources and to implement fault-tolerant logical qubits. The proposal focuses on two specific targets, which represent crucial milestones for the realization of such magnetic quantum processor. The first is the implementation of quantum error correction codes in molecular structures. The second is the attainment of strong, or coherent, coupling between an individual molecular spin and a single photon trapped in a resonator. Progress towards these targets involves a coordinated cooperation between diverse disciplines and between experimental and theoretical methods. Coordination and supramolecular chemistry will be combined to design and synthesize molecular structures hosting multiple qubits. Spin relaxation T1 and coherence T2 times of these systems will be measured by state-of-the-art electron paramagnetic spectroscopy and optimized, by means of chemical methods, to values exceeding 100 microseconds that are required both to overcome the error correction coherence thresholds and attain strong coupling to a superconducting resonator. A new generation of microwave superconducting nanoresonators, able to squeeze microwave magnetic fields into nanoscopic regions, will be developed by either milling down the central transmission line with ion-beam nanolithography or by fabricating nanobridges with single-wall carbon nanotubes or two-dimensional superconducting layers. Molecules will be nanopatterned into these devices by a combination of dip-pen nanolithography and the use of surface-reacting molecular ligands. Coherence times of individual molecules bond to superconducting substrates will be determined at low temperatures by STM-based pump-probe experiments. The final goal is to perform circuit QED experiments on individual molecular spins to achieve the strong coupling regime, provide proof-of-concept implementations of basic quantum operations and read-out their quantum spin states.