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Experimental four-qubit bound entanglement

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Abstract

Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information. Being a peculiar form of entanglement, bound entanglement emerges in certain mixed quantum states. This form of entanglement is not distillable by local operators and classical communication. Bound-entangled states are different from both the free entangled (distillable) and separable states. Here we report on the first experimental demonstration of a four-qubit polarization bound-entangled state, the so-called Smolin state. We have fully characterized its entanglement properties. Moreover, we have realized unlocking of the entanglement protocol for this state. The special properties of the Smolin state constitute a useful quantum resource for new multiparty communication schemes.

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Figure 1: Experimental set-up for the generation of a four-qubit polarization bound-entangled state.
Figure 2: Experimental results: the density matrix.
Figure 3: Entanglement-distillation scheme.
Figure 4: Experimental set-up for Bell measurement.
Figure 5: Experimental results for the entanglement distillation.

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References

  1. Einstein, A., Podolsky, B. & Rosen, N. Can quantum-mechanical description of physical reality be considered complete? Phys. Rev. 47, 777–780 (1935).

    Article  ADS  Google Scholar 

  2. Bell, J. S. On the Einstein–Podolsky–Rosen paradox. Physics 1, 195–200 (1964).

    Article  MathSciNet  Google Scholar 

  3. Peres, A. Separability criterion for density matrices. Phys. Rev. Lett. 77, 1413–1415 (1996).

    Article  ADS  MathSciNet  Google Scholar 

  4. Horodecki, M., Horodecki, P. & Horodecki, R. Separability of mixed states: Necessary and sufficient conditions. Phys. Lett. A 223, 1–8 (1996).

    Article  ADS  MathSciNet  Google Scholar 

  5. Zurek, W. H. Decoherence and the transition from quantum to classical. Phys. Today 44, 36–44 (1991).

    Article  Google Scholar 

  6. Horodecki, M., Horodecki, P. & Horodecki, R. Inseparable two spin-(1/2) density matrices can be distilled to a singlet form. Phys. Rev. Lett. 78, 574–577 (1997).

    Article  ADS  Google Scholar 

  7. Bennett, C. H. et al. Purification of noisy entanglement and faithful teleportation via noisy channels. Phys. Rev. Lett. 76, 722–725 (1996).

    Article  ADS  Google Scholar 

  8. Horodecki, P. Separability criterion and inseparability mixed states with positive partial transposition. Phys. Lett. A 232, 333–339 (1997).

    Article  ADS  MathSciNet  Google Scholar 

  9. Horodecki, M., Horodecki, P. & Horodecki, R. Mixed-state entanglement and distillation: Is there a bound entanglement in nature? Phys. Rev. Lett. 80, 5239–5242 (1998).

    Article  ADS  MathSciNet  Google Scholar 

  10. Tóth, G., Knapp, Ch., Gühne, O. & Briegel, H. J. Optimal spin squeezing inequalities detect bound entanglement in spin models. Phys. Rev. Lett. 99, 250405 (2007).

    Article  ADS  Google Scholar 

  11. Ferraro, A., Cavalcanti, D., Garía-Saez, A. & Acin, A. Thermal bound entanglement in macroscopic systems and area law. Phys. Rev. Lett. 100, 080502 (2008).

    Article  ADS  Google Scholar 

  12. Acin, A., Cirac, J. I. & Masanes, Li. Multipartite bound information exists and can be activated. Phys. Rev. Lett. 92, 107903 (2004).

    Article  ADS  Google Scholar 

  13. Smolin, J. A. Four-party unlockable bound entangled state. Phys. Rev. A 63, 032306 (2001).

    Article  ADS  Google Scholar 

  14. Shor, P. W., Smolin, J. A. & Thapliyal, A. V. Superactivation of bound entanglement. Phys. Rev. Lett. 90, 107901 (2003).

    Article  ADS  MathSciNet  Google Scholar 

  15. Augusiak, R. & Horodecki, P. Generalized Smolin state and their properties. Phys. Rev. A 73, 012318 (2006).

    Article  ADS  MathSciNet  Google Scholar 

  16. Murao, M. & Vedral, V. Remote information concentration using a bound entangled state. Phys. Rev. Lett. 86, 352–355 (2001).

    Article  ADS  Google Scholar 

  17. Augusiak, R. & Horodecki, P. Bound entanglement maximally violating Bell inequalities: Quantum entanglement is not full equivalent to cryptographic security. Phys. Rev. A 74, 010305 (2006).

    Article  ADS  Google Scholar 

  18. Brukner, Č., Zukowski, M., Pan, J.-W. & Zeilinger, A. Bell’s inequalities and quantum communication complexity. Phys. Rev. Lett. 92, 127901 (2004).

    Article  ADS  MathSciNet  Google Scholar 

  19. Wang, G. & Ying, M. Multipartite unlockable bound entanglement in the stabilizer formalism. Phys. Rev. A 75, 052332 (2007).

    Article  ADS  Google Scholar 

  20. Kwiat, P. G. et al. New high intensity source of polarization-entangled photon pairs. Phys. Rev. Lett. 75, 4337–4341 (1995).

    Article  ADS  Google Scholar 

  21. James, D. F., Kwiat, P. G., Munro, W. J. & White, A. Measurement of qubits. Phys. Rev. A 64, 052312 (2001).

    Article  ADS  Google Scholar 

  22. Tóth, G. & Gühne, O. Entanglement detection in stabilizer formalism. Phys. Rev. A 72, 022340 (2005).

    Article  ADS  Google Scholar 

  23. Braunstein, S. L., Mann, A. & Revzen, M. Maximal violation of Bell inequalities for mixed states. Phys. Rev. Lett. 68, 3259–3261 (1992).

    Article  ADS  MathSciNet  Google Scholar 

  24. Kiesel, N. et al. Linear optics controlled-phase gate made simple. Phys. Rev. Lett. 95, 210505 (2005).

    Article  ADS  Google Scholar 

  25. Lewenstein, M., Kraus, B., Cirac, J. I. & Horodecki, P. Optimization of entanglement witnesses. Phys. Rev. A 62, 052310 (2000).

    Article  ADS  Google Scholar 

  26. Gühne, O. et al. Detection of entanglement with few local measurements. Phys. Rev. A 66, 062305 (2002).

    Article  ADS  Google Scholar 

  27. Tóth, G. QUBIT4MATLAB V3.0: A program package for quantum information science and quantum optics for MATLAB. Comput. Phys. Commun. 179, 430–437 (2008).

    Article  ADS  MathSciNet  Google Scholar 

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Acknowledgements

We acknowledge support by the Swedish Research Council (Vetenskapsrådet).

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Authors and Affiliations

  1. Physics Department, Stockholm University, S-10691, Stockholm, Sweden

    Elias Amselem & Mohamed Bourennane

Authors
  1. Elias Amselem
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  2. Mohamed Bourennane
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Contributions

E.A. carried out the experiment. E.A. and M.B. discussed the results and wrote the manuscript. M.B. supervised the project.

Corresponding author

Correspondence to Mohamed Bourennane.

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Amselem, E., Bourennane, M. Experimental four-qubit bound entanglement. Nature Phys 5, 748–752 (2009). https://doi.org/10.1038/nphys1372

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