A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor

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Abstract

One proposal for a solid-state-based quantum bit (qubit) is to control coupled electron spins on adjacent semiconductor quantum dots1,2. Most experiments have focused on quantum dots made from III–V semiconductors; however, the coherence of electron spins in these materials is limited by hyperfine interactions with nuclear spins3,4,5,6. Ge/Si core/shell nanowires seem ideally suited to overcome this limitation, because the most abundant nuclei in Ge and Si have spin zero and the nanowires can be chemically synthesized defect-free with tunable properties7. Here, we present a double quantum dot based on Ge/Si nanowires in which we can completely control the coupling between the dots and to the leads. We also demonstrate that charge on the double dot can be detected by coupling it capacitively to an adjacent nanowire quantum dot. The double quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit free of nuclear spin.

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Figure 1: Ge/Si nanowire double dot device and demonstration of tunable interdot coupling.
Figure 2: Simultaneous transport and charge sensing measurements.
Figure 3: Charge sensing of an isolated double dot.
Figure 4: Interdot tunnelling measured with the charge sensor.

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Acknowledgements

We thank L. DiCarlo and E. A. Laird for experimental assistance and helpful discussions. C.M.L. acknowledges support from the Defense Advanced Research Projects Agency and Samsung Electronics. C.M.M. acknowledges support from the Disruptive Technology Office. H.O.H.C. acknowledges support from the National Science Foundation.

Author information

Y.H. and H.O.H.C. performed the experiments. Y.H. and J.X. fabricated the devices. Y.H., H.O.H.C., D.J.R., C.M.L. and C.M.M. analysed the data and co-wrote the paper. All authors discussed the results and commented on the manuscript.

Correspondence to Charles M. Lieber or Charles M. Marcus.

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Hu, Y., Churchill, H., Reilly, D. et al. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor. Nature Nanotech 2, 622–625 (2007) doi:10.1038/nnano.2007.302

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