Abstract
The representation of information within the spins of electrons and nuclei has been a powerful method in the ongoing development of quantum computers1,2. Although nuclear spins are advantageous as quantum bits (qubits) because of their long coherence lifetimes (exceeding seconds3), they exhibit very slow spin interactions and have weak thermal polarization. A coupled electron spin can be used to polarize the nuclear spin4,5,6 and create fast single-qubit gates7,8, however, the permanent presence of electron spins is a source of nuclear decoherence. Here we show how a transient electron spin, arising from the optically excited triplet state of C60, can be used to hyperpolarize, manipulate and measure two nearby nuclear spins. Implementing a scheme that uses the spinor nature of the electron9, we performed an entangling gate in hundreds of nanoseconds: five orders of magnitude faster than the liquid-state J coupling. This approach can be widely applied to systems comprising an electron spin coupled to multiple nuclear spins, such as nitrogen–vacancy centres in diamond10, while the successful use of a transient electron spin motivates the design of new molecules able to exploit photoexcited triplet states.
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Acknowledgements
We thank B. Lovett, M. Schaffry, E. Gauger, C. Kay, A. Ardavan, A. Briggs and D. Ceresoli for helpful discussions. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) through the Centre for Advanced Electron Spin Resonance (CAESR) (EP/D048559/1) and the Materials World Network (EP/I035536/1), as well as by the European Research Council (ERC) under the European Community’s Seventh Framework Programme (FP7/2,007-2,013)/ERC grant agreement no. 279,781. We thank the Violette and Samuel Glasstone Fund, Clarendon Fund, John Templeton Foundation, St John’s College, Oxford, and the Royal Society for support.
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V.F., S.S. and J.J.L.M. designed and performed the experiments, analysed the results and wrote the manuscript. V.F. and F.G. performed the density functional calculations. S.D.K. and H.L.A. designed and synthesised the molecule. All authors discussed the results and manuscript.
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Filidou, V., Simmons, S., Karlen, S. et al. Ultrafast entangling gates between nuclear spins using photoexcited triplet states. Nature Phys 8, 596–600 (2012). https://doi.org/10.1038/nphys2353
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DOI: https://doi.org/10.1038/nphys2353
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