Resubmission of IMPRESS: Intra-Molecular Propagation of Electron Spin States

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There is an intense worldwide search, spanning both academic and commercial sectors, to find a realistic route toward computing with molecular scale structures. The International Technology Roadmap for Semiconductors (public.itrs.net), a definitive document for the electronics industry, now recognises that conventional 'top-down' technologies may have a limited remaining lifespan. It advocates a search for next generation technologies, recognising that molecular scale computation is an exceptionally promising prospect. It further highlights quantum information processing (QIP), the technology that would result from manipulating coherent superpositions of states, as having immense potential for certain applications. The research we describe here aims to create prototype elements for technologies of those classes.Project IMPRESS is concerned with the electron spin states within individual nanostructures, specifically carbon nanotube 'peapods'. Through a variety of characterisation techniques, and pioneering synthetic chemistry, we will develop the ability to engineer spin-spin interactions along a one-dimensional chain of intra-tube spins. Recent high-profile theoretical studies have shown that such a spin chain would have highly remarkable properties. It would be capable of rapidly transferring the spin states, i.e. the information, along the chain purely by virtue of the spin-spin interactions without any externally applied voltage or power dissipation. Moreover it is even possible to generate multi-spin entanglement, the underlying resource for QIP, purely through the free evolution of such a chain. Thus a molecular device of this kind could constitute a key building block for any technology based on information processing with electron spins, especially QIP.