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The initialization and manipulation of quantum information stored in silicon by bismuth dopants


A prerequisite for exploiting spins for quantum data storage and processing is long spin coherence times. Phosphorus dopants in silicon (Si:P) have been favoured1,2,3,4,5,6,7,8,9,10 as hosts for such spins because of measured electron spin coherence times (T2) longer than any other electron spin in the solid state: 14 ms at 7 K with isotopically purified silicon11. Heavier impurities such as bismuth in silicon (Si:Bi) could be used in conjunction with Si:P for quantum information proposals that require two separately addressable spin species12,13,14,15. However, the question of whether the incorporation of the much less soluble Bi into Si leads to defect species that destroy coherence has not been addressed. Here we show that schemes involving Si:Bi are indeed feasible as the electron spin coherence time T2 is at least as long as for Si:P with non-isotopically purified silicon. We polarized the Si:Bi electrons and hyperpolarized the I=9/2 nuclear spin of 209Bi, manipulating both with pulsed magnetic resonance. The larger nuclear spin means that a Si:Bi dopant provides a 20-dimensional Hilbert space rather than the four-dimensional Hilbert space of an I=1/2 Si:P dopant.

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Figure 1: Qubit initialization.
Figure 2: Qubit manipulation.
Figure 3: Storage of quantum information.
Figure 4: Storage times for classical (T1) and quantum (T2) information.


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We thank B. Pajot for supplying the Si:Bi samples. Our research was supported by the RCUK Basic Technologies programme, the EPSRC programme grant COMPASSS and a Wolfson Royal Society Research Merit Award. The National High Magnetic Field Laboratory is supported by NSF Cooperative Agreement No. DMR-0654118, and by the State of Florida. G.W.M. is supported by an 1851 Research Fellowship.

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G.W.M., M.W. and C.W.M.K. carried out the experiments at 9.7 GHz; G.W.M. and J.v.T. carried out the experiments at 240 GHz. G.W.M. and P.T.G. carried out the simulations. G.W.M. analysed the data, which were interpreted by G.W.M., A.M.S., J.v.T., C.W.M.K. and G.A. The Letter was written by G.W.M., A.M.S., J.v.T., C.W.M.K. and G.A.

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Correspondence to Gavin W. Morley.

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Morley, G., Warner, M., Stoneham, A. et al. The initialization and manipulation of quantum information stored in silicon by bismuth dopants. Nature Mater 9, 725–729 (2010).

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