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Demonstration of genuine multipartite entanglement with device-independent witnesses

Abstract

Entanglement in a quantum system can be demonstrated experimentally by performing the measurements prescribed by an appropriate entanglement witness. However, the unavoidable mismatch between the implementation of measurements in practical devices and their precise theoretical modelling generally results in the undesired possibility of false-positive entanglement detection. Such scenarios can be avoided by using the recently developed device-independent entanglement witnesses (DIEWs) for genuine multipartite entanglement. Similarly to Bell inequalities, the only assumption of DIEWs is that consistent measurements are performed locally on each subsystem. No precise description of the measurement devices is required. Here we report an experimental test of DIEWs on up to six entangled 40Ca+ ions. We also demonstrate genuine multipartite quantum nonlocality between up to six parties with the detection loophole closed.

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Figure 1: State and measurement characterization for the six-qubit DIEW measurement.

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Acknowledgements

We thank Y-C. Liang for useful discussions. We gratefully acknowledge support by the Austrian Science Fund (FWF) through the SFB FoQuS (FWF Project No. F4006-N16) and by the Swiss NCCR ‘Quantum Science and Technology’, the CHIST-ERA DIQIP, and the European ERC-AG QORE. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), through the Army Research Office grant W911NF-10-1-0284. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of IARPA, the ODNI, or the US Government.

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Contributions

J.T.B. and J-D.B. developed the research; J.T.B., P.S. and D.N. performed the experiments; J-D.B. and N.G. provided the theoretical part; J.T.B., J-D.B., T.M. and P.S. analysed the data; J.T.B., P.S., D.N., T.M., M.H. and R.B. contributed to the experimental set-up; J.T.B. and J-D.B. wrote the manuscript, with revisions provided by P.S., T.M., N.G. and R.B; all authors contributed to the discussion of the results and manuscript.

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Correspondence to Julio T. Barreiro or Jean-Daniel Bancal.

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The authors declare no competing financial interests.

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Barreiro, J., Bancal, JD., Schindler, P. et al. Demonstration of genuine multipartite entanglement with device-independent witnesses. Nature Phys 9, 559–562 (2013). https://doi.org/10.1038/nphys2705

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