Scaling Up quantum computation with Molecular spins

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.

Schemes that use superconducting qubits are pursued by companies such as Google and IBM. Scaling-up this technology involves huge economic investments that might reach several billion $.8 Building on the long standing European leadership in Molecular Magnetism, SUMO opens alternative paths to handle high quantum information densities through the use of low-cost, yet powerful, chemical methods to fabricate the basic components and integrate them in devices. The experimental techniques (rational synthesis of functional molecules, nanopatterning, single-molecule magnetic spectroscopy) and devices (microwave quantum nanocircuits) will be useful for chemical and biomedical industries as well as for electronics and sensing.

SUMO ensures proper dissemination of results by publication in highly rated scientific journals, promoting scientific exchanges with other groups and participating in specialised conferences on our field and adjacent areas. It will also ensure open access to publications by offering a database on the project's webpage and encouraging open-access publication in arXiv.org and local repositories. The project will generate: a) results of experiments and theoretical studies and b) technical reports describing molecular and circuit designs and novel experimental methods. A data management plan, establishing which data need adequate protection and which can be made available to researchers worldwide, will be elaborated within the first six months. It will also set the electronic platform used to disseminate them. While still in an exploratory phase, the possibility of knowledge transfer towards the industry is likely. SUMO supports exploring the potential of our research during its realisation and prior to publication. This requires a precise coordination of the partners and their IPR policies, which will be detailed in the consortium agreement contract.
The management structure (WP6) establishes proper communication channels among the project members, which include email or videoconferencing and a kick-off and two progress meetings among all project members. Main communication channels to the scientific community are high-impact open-access publications, the open dissemination of data, the participation at international conferences and the promotion of exchange visits and seminars, mainly with prominent researchers working on quantum ICT and related areas to help establishing strategic collaborations. We will also establish an attractive web presence, accessible to the general public, participate in local science fairs, talks and courses at universities and high-schools, report to local scientific authorities, lobbying for the field of quantum information with magnetic molecules, and issue formal press notes to get proper coverage of our greatest milestones. We shall also identify potential industrial partners, devote a webpage section to discuss the commercial potential of the field, and use our knowledge transfer offices as well as the European Institute of Molecular Magnetism to advertise our results to the European industry.