On-demand single-electron transfer between distant quantum dots


Single-electron circuits of the future, consisting of a network of quantum dots, will require a mechanism to transport electrons from one functional part of the circuit to another. For example, in a quantum computer1 decoherence and circuit complexity can be reduced by separating quantum bit (qubit) manipulation from measurement and by providing a means of transporting electrons between the corresponding parts of the circuit2. Highly controlled tunnelling between neighbouring dots has been demonstrated3,4, and our ability to manipulate electrons in single- and double-dot systems is improving rapidly5,6,7,8. For distances greater than a few hundred nanometres, neither free propagation nor tunnelling is viable while maintaining confinement of single electrons. Here we show how a single electron may be captured in a surface acoustic wave minimum and transferred from one quantum dot to a second, unoccupied, dot along a long, empty channel. The transfer direction may be reversed and the same electron moved back and forth more than sixty times—a cumulative distance of 0.25 mm—without error. Such on-chip transfer extends communication between quantum dots to a range that may allow the integration of discrete quantum information processing components and devices.

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Figure 1: Device, initialization and single-electron transfer.
Figure 2: Single-electron transfer reliability.
Figure 3: Dependence of LQD depopulation on SAW power and pulse width.
Figure 4: Backscattering of electrons in the RQD due to SAW(L).


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The authors acknowledge funding from the UK EPSRC, Toshiba Research Europe Limited and QIPIRC.

Author information

R.P.G.M., M.K., C.J.B.F. and C.H.W.B. designed the experiment; I.F. and D.A.R. provided wafers; D.A. and G.A.C.J. performed electron-beam lithography; R.P.G.M. processed samples and analysed data; R.P.G.M. and M.K. performed experiments; R.P.G.M., C.J.B.F. and M.K. wrote the paper.

Correspondence to C. J. B. Ford.

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The authors declare no competing financial interests.

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McNeil, R., Kataoka, M., Ford, C. et al. On-demand single-electron transfer between distant quantum dots. Nature 477, 439–442 (2011). https://doi.org/10.1038/nature10444

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