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Positive noise cross-correlation in hybrid superconducting and normal-metal three-terminal devices

Nature Physics volume 6, pages 494–498 (2010)Cite this article

Abstract

Non-local entanglement is a key ingredient to quantum information processing. For photons, entanglement has been demonstrated1, but it is more difficult to observe for electrons. One approach is to use a superconductor, where electrons form spin-entangled Cooper pairs, which is a natural source for entangled electrons. For a three-terminal device consisting of a superconductor sandwiched between two normal metals, it has been predicted that Cooper pairs can split into spin-entangled electrons flowing in the two spatially separated normal metals2,3,4,5, resulting in a negative non-local resistance and a positive current–current correlation6,7. The former prosperity has been observed8,9, but not the latter. Here we show that both characteristics can be observed, consistent with Cooper-pair splitting. Moreover, the splitting efficiency can be tuned by independently controlling the energy of the electrons passing the two superconductor/normal-metal interfaces, which may lead to better understanding and control of non-local entanglement.

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Figure 1: Schematic of the cross-correlation measurement.
Figure 2: Junction characterization.
Figure 3: Bias current dependence of voltage noise power by the cross-correlation measurement.
Figure 4: Bias current dependence of local and non-local differential resistance.

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Acknowledgements

We thank M. Büttiker, W. Belzig and A. Levy Yeyati for comments on our preprint. This work was sponsored by the National Science Foundation through grant no. DMR-0604601.

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Authors and Affiliations

  1. Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA

    Jian Wei & V. Chandrasekhar

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  1. Jian Wei
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  2. V. Chandrasekhar
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Contributions

J.W. fabricated samples and carried out measurements and analysis. J.W. and V.C. prepared the manuscript.

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Correspondence to Jian Wei or V. Chandrasekhar.

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The authors declare no competing financial interests.

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Wei, J., Chandrasekhar, V. Positive noise cross-correlation in hybrid superconducting and normal-metal three-terminal devices. Nature Phys 6, 494–498 (2010). https://doi.org/10.1038/nphys1669

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