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Quantum control of hybrid nuclear–electronic qubits


Pulsed magnetic resonance allows the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively1. The time required to flip dilute spins is orders of magnitude shorter than their coherence times2,3,4,5,6,7,8,9, leading to several schemes for quantum information processing with spin qubits10,11,12,13. Instead, we investigate ‘hybrid nuclear–electronic’ qubits14,15 consisting of near 50:50 superpositions of the electronic and nuclear spin states. Using bismuth-doped silicon, we demonstrate quantum control over these states in 32 ns, which is orders of magnitude faster than previous experiments using pure nuclear states2,3. The coherence times of up to 4 ms are five orders of magnitude longer than the manipulation times, and are limited only by naturally occurring 29Si nuclear spin impurities. We find a quantitative agreement between our experiments and an analytical theory for the resonance positions, as well as their relative intensities and Rabi oscillation frequencies. These results bring spins in a solid material a step closer to research on ion-trap qubits10.

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Figure 1: Spectroscopy of hybrid nuclear–electronic qubits.
Figure 2: Fast quantum control of hybrid nuclear–electronic qubits.
Figure 3: Coherence times of hybrid nuclear–electronic qubits.

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We acknowledge Bernard Pajot for the Si:Bi crystal used here, R. Tschaggelar for technical assistance, the National EPR Facility and Service at the University of Manchester, UK, for initial continuous-wave experiments at 4 GHz and the EPSRC COMPASSS grant. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. G.W.M. is supported by the Royal Commission for the Exhibition of 1851 and the Royal Society.

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G.W.M. and T.S.M. designed the study within the overall research programme on Si:Bi defined by C.W.M.K. and G.A., and wrote the paper with input and corrections from all authors. P.L. performed the experiments with assistance from G.W.M. and M.H.M., and supervision from G.J. G.W.M. analysed the data. S.J.B. and W.M.W. performed the cluster correlation expansion simulations.

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Correspondence to Gavin W. Morley.

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Morley, G., Lueders, P., Hamed Mohammady, M. et al. Quantum control of hybrid nuclear–electronic qubits. Nature Mater 12, 103–107 (2013).

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