hybroqubits · developing hybrid organic-inorganic rotaxanes for quantum information processing

developing hybrid organic-inorganic rotaxanes for quantum information processing

1. Final Publishable Summary Report The proposed project was based on recent results reported (Nature 2009, 458, 314; J. Am. Chem.Soc., 2010, 132, 15435) by the Winpenny group where they showed that heterometallic rings could be grown around organic threads, producing a new form of rotaxanes with both inorganic and organic components. [3]-rotaxanes could be made as prototypes for two qubit gates for quantum computers. Quantum computers will use quantum binary digits, or qubits (the quantum analogue of the classical bit). Their complexity will enable to perform calculations with speeds of 106 times faster than the average PC. A key question is how to link qubits to entangle spins without causing decoherence; The Winpenny group et al. showed that using organic and inorganic components at the molecular level, they could link two molecular nanomagnet prototype qubits into a structure where, depending on the link, they can either communicate or not (Nat. Nanotech. 2009, 4,173). In our proposal we suggested an innovative approach to build two qubit rotaxanes that could become part of future devices. [3]-rotaxane provides the ideal framework for making a scalable two qubit gate, because we can develop the two components of the rotaxane separately and then combine in the final structure. The advantages over other solid state systems: -The chemistry is cheap and reliable -Allows multiple chemical functions to be incorporated -Excited states in heterometallic rings can be an additional resource involving multiple qubits. Physical studies were made with pulsed EPR spectroscopy both in ground and excited states to measure relaxation times, varying factors like solvent that can influence relaxation times.We synthesized and characterised by NMR and X-ray crystallography a range of different types of [3]-rotaxanes (see Figure Attached), varying the rigidity and the distance between the rings, in order to study the through space interaction, how the decoherence times depend on inter-ring distance. We have been trying to minimize the dipolar contribution to decoherence by control of the separation of the two antiferromagnetic rings in the [3]-rotaxane. In parallel to that, we synthesized several substituted rings with different functionalities and currently we are studying their inclusion in threads as rotaxanes and this has been proven the most challenging task so far. We are considering several alternatives. We have also examined attachment of rotaxanes to surfaces by atomic force microscopy and other methods. The compounds can be deposited from solution phase intact. All the standard equipment required to carry out synthetic chemistry are to hand and all departmental facilities (NMR, x-ray crystallography, etc.) are freely available. The progress of this research project has been monitored during weekly group meetings. A more formal review of progress has involved an annual performance review conducted by Prof Richard Winpenny. The milestones already achieved: Year 1: - Synthesis and crystallisation of [3]-rotaxanes with different threads including {Cr7M} rings with M = Ni,Co, and their characterisation - Pulsed EPR studies of [3]-rotaxanes - Functionalization and deposition of [2]-rotaxanes and [3]-rotaxanes on gold surface Year 2: - Synthesis of several substituted rings with different functionalities - Characterisation of substituted rings that include communication straps by NMR and X-ray crystallography - Electrochemical and EPR spectroscopic studies of the new systems

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