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Experimental long-lived entanglement of two macroscopic objects

Nature volume 413, pages 400–403 (2001)Cite this article

Abstract

Entanglement is considered to be one of the most profound features of quantum mechanics1,2. An entangled state of a system consisting of two subsystems cannot be described as a product of the quantum states of the two subsystems3,4,5,6. In this sense, the entangled system is considered inseparable and non-local. It is generally believed that entanglement is usually manifest in systems consisting of a small number of microscopic particles. Here we demonstrate experimentally the entanglement of two macroscopic objects, each consisting of a caesium gas sample containing about 1012 atoms. Entanglement is generated via interaction of the samples with a pulse of light, which performs a non-local Bell measurement on the collective spins of the samples7. The entangled spin-state can be maintained for 0.5 milliseconds. Besides being of fundamental interest, we expect the robust and long-lived entanglement of material objects demonstrated here to be useful in quantum information processing, including teleportation8,9,10 of quantum states of matter and quantum memory.

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Figure 1: The experimental set-up, atomic level structure and the sequence of optical pulses.
Figure 2: Determination of the coherent spin state limit for entanglement.
Figure 3: Demonstration of the entangled spin state for two atomic samples.

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References

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

    Article  ADS  CAS  Google Scholar 

  2. Bell, J. S. Speakable and Unspeakable in Quantum Mechanics (Cambridge Univ. Press, Cambridge, 1988).

    MATH  Google Scholar 

  3. Aspect, A., Dalibard, J. & Roger, G. Experimental test of Bell's inequalities using time-varying analyzers. Phys. Rev. Lett. 49, 1804–1807 (1982).

    Article  ADS  MathSciNet  Google Scholar 

  4. Togerson, J. R., Branning, D., Monken, C. H. & Mandel, L. Experimental demonstration of the violation of local realism without Bell inequalities. Phys. Lett. A 204, 323–328 (1995).

    Article  ADS  Google Scholar 

  5. Duan, Lu. M., Giedke, G., Cirac, J. I. & Zoller, P. Inseparability criterion for continuous variable systems. Phys. Rev. Lett. 84, 2722–2725 (2000).

    Article  ADS  CAS  Google Scholar 

  6. Simon, R. Peres-Horodecki separability criterion for continuous variable systems. Phys. Rev. Lett. 84, 2726–2729 (2000).

    Article  ADS  CAS  Google Scholar 

  7. Duan, L. M., Cirac, J. I., Zoller, P. & Polzik, E. S. Phys. Rev. Lett. 85, 5643–5646 (2000).

    Article  ADS  CAS  Google Scholar 

  8. Bouwmeester, D., Pan, J. W., Mattle, K., Eibl, M., Weinfurter, H. & Zeilinger, A. Experimental quantum teleportation. Nature 390, 575–579 (1997).

    Article  ADS  CAS  Google Scholar 

  9. Boschi, D., Branca, S., De Martini, F., Hardy, L. & Popescu, S. Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels. Phys. Rev. Lett. 80, 1121–1125 (1998).

    Article  ADS  MathSciNet  CAS  Google Scholar 

  10. Furusawa, A. et al. Unconditional quantum teleportation. Science 282, 706–709 (1998).

    Article  ADS  CAS  Google Scholar 

  11. Mattle, K., Weinfurter, H., Kwiat, P. G. & Zeilinger, A. Dense coding in experimental quantum communication. Phys. Rev. Lett. 76, 4656–4659 (1996).

    Article  ADS  CAS  Google Scholar 

  12. Braunstein, S. L. & Kimble, H. J. Dense coding for continuous variables. Phys. Rev. A 61, 042302 (2000).

    Article  ADS  MathSciNet  Google Scholar 

  13. Ban, M. Quantum dense coding via a two-mode squeezed-vacuum state. J. Opt. B 1, L9–L11 (1999).

    Article  ADS  Google Scholar 

  14. Ou, Z. Y., Pereira, S. F., Kimble, H. J. & Peng, K. C. Realization of the Einstein-Podolsky-Rosen paradox for continuous variables. Phys. Rev. Lett. 68, 3663–3666 (1992).

    Article  ADS  CAS  Google Scholar 

  15. Sackett, C. A. et al. Experimental entanglement of four particles. Nature 404, 256–259 (2000).

    Article  ADS  CAS  Google Scholar 

  16. Rauschenbeutel, A. et al. Step-by-step engineered multiparticle entanglement. Science 288, 2024–2028 (2000).

    Article  ADS  CAS  Google Scholar 

  17. Kuzmich, A. & Polzik, E. S. Atomic quantum state teleportation and swapping. Phys. Rev. Lett. 85, 5639–5642 (2000).

    Article  ADS  CAS  Google Scholar 

  18. Kitagawa, M. & Ueda, M. Spin squeezed states. Phys. Rev. A 47, 5138–5143 (1993).

    Article  ADS  CAS  Google Scholar 

  19. Wineland, D. J., Bollinger, J. J., Itano, W. M., Moore, F. L. & Jeomzem., D. J. Spin squeezing and reduced quantum noise in spectroscopy. Phys. Rev. A 46, R6797–R6800 (1992).

    Article  ADS  CAS  Google Scholar 

  20. Kupriyanov, D. V. & Sokolov, I. M. Optical detection of magnetic resonance by classical and squeezed light. Quant. Opt. 4, 55–70 (1992).

    Article  ADS  Google Scholar 

  21. Hald, J., Sørensen, J. L., Schori, C. & Polzik, E. S. Spin squeezed atoms: a macroscopic entangled ensemble created by light. Phys. Rev. Lett. 83, 1319–1322 (1999).

    Article  ADS  Google Scholar 

  22. Kuzmich, A., Mandel, L. & Bigelow, N. P. Generation of spin squeezing via continuous quantum nondemolition measurement. Phys. Rev. Lett. 85, 1594–1597 (2000).

    Article  ADS  CAS  Google Scholar 

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Acknowledgements

We gratefully acknowledge the contributions of J. Hald, J. L. Sørensen, C. Schori and A. Verchovski. We also thank I. Cirac, A. Kuzmich, A. Sørensen and P. Zoller for discussions.

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  1. Institute of Physics and Astronomy, University of Aarhus, Aarhus, 8000, Denmark

    Brian Julsgaard, Alexander Kozhekin & Eugene S. Polzik

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  1. Brian Julsgaard
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Correspondence to Eugene S. Polzik.

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Julsgaard, B., Kozhekin, A. & Polzik, E. Experimental long-lived entanglement of two macroscopic objects. Nature 413, 400–403 (2001). https://doi.org/10.1038/35096524

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