Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Tunable delay of Einstein–Podolsky–Rosen entanglement


Entangled systems display correlations that are stronger than can be obtained classically. This makes entanglement an essential resource for a number of applications, such as quantum information processing, quantum computing and quantum communications1,2. The ability to control the transfer of entanglement between different locations will play a key role in these quantum protocols and enable quantum networks3. Such a transfer requires a system that can delay quantum correlations without significant degradation, effectively acting as a short-term quantum memory. An important benchmark for such systems is the ability to delay Einstein–Podolsky–Rosen (EPR) levels of entanglement and to be able to tune the delay. EPR entanglement is the basis for a number of quantum protocols, allowing the remote inference of the properties of one system (to better than its standard quantum limit) through measurements on the other correlated system. Here we show that a four-wave mixing process based on a double-lambda scheme in hot 85Rb vapour allows us to obtain an optically tunable delay for EPR entangled beams of light. A significant maximum delay, of the order of the width of the cross-correlation function, is achieved. The four-wave mixing also preserves the quantum spatial correlations of the entangled beams. We take advantage of this property to delay entangled images, making this the first step towards a quantum memory for images4.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Experimental set-up.
Figure 2: Delay of EPR entanglement.
Figure 3: Effect of the gain in the slow light cell on the quantum correlations.
Figure 4: Delay of an entangled image of the ‘ ’ symbol.


  1. Galindo, A. & Martin-Delgado, M. A. Information and computation: Classical and quantum aspects. Rev. Mod. Phys. 74, 347–423 (2002)

    ADS  MathSciNet  Article  Google Scholar 

  2. Braunstein, S. L. & van Loock, P. Quantum information with continuous variables. Rev. Mod. Phys. 77, 513–577 (2005)

    ADS  MathSciNet  Article  Google Scholar 

  3. Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008)

    ADS  CAS  Article  Google Scholar 

  4. Vasilyev, D. V., Sokolov, I. V. & Polzik, E. S. Quantum memory for images: A quantum hologram. Phys. Rev. A 77, 020302(R) (2008)

    ADS  Article  Google Scholar 

  5. Hau, L. V., Harris, S. E., Dutton, Z. & Behroozi, C. H. Light speed reduction to 17 metres per second in an ultracold atomic gas. Nature 397, 594–598 (1999)

    ADS  CAS  Article  Google Scholar 

  6. Camacho, R. M., Pack, M. V., Howell, J. C., Schweinsberg, A. & Boyd, R. W. Wide-bandwidth, tunable, multiple-pulse-width optical delays using slow light in cesium vapor. Phys. Rev. Lett. 98, 153601 (2007)

    ADS  Article  Google Scholar 

  7. Boyer, V., McCormick, C. F., Arimondo, E. & Lett, P. D. Ultraslow propagation of matched pulses by four-wave mixing in an atomic vapor. Phys. Rev. Lett. 99, 143601 (2007)

    ADS  CAS  Article  Google Scholar 

  8. Broadbent, C. J., Camacho, R. M., Xin, R. & Howell, J. C. Preservation of energy-time entanglement in a slow light medium. Phys. Rev. Lett. 100, 133602 (2008)

    ADS  Article  Google Scholar 

  9. Chaneliere, T. et al. Storage and retrieval of single photons transmitted between remote quantum memories. Nature 438, 833–836 (2005)

    ADS  CAS  Article  Google Scholar 

  10. Eisaman, M. D. et al. Electromagnetically induced transparency with tunable single-photon pulses. Nature 438, 837–841 (2005)

    ADS  CAS  Article  Google Scholar 

  11. Choi, K. S., Deng, H., Laurat, J. & Kimble, H. J. Mapping photonic entanglement into and out of a quantum memory. Nature 452, 67–71 (2008)

    ADS  CAS  Article  Google Scholar 

  12. Akamatsu, D. et al. Ultraslow propagation of squeezed vacuum pulses with electromagnetically induced transparency. Phys. Rev. Lett. 99, 153602 (2007)

    ADS  Article  Google Scholar 

  13. Honda, K. et al. Storage and retrieval of a squeezed vacuum. Phys. Rev. Lett. 100, 093601 (2008)

    ADS  Article  Google Scholar 

  14. Appel, J., Figueroa, E., Korystov, D., Lobino, M. & Lvovsky, A. I. Quantum memory for squeezed light. Phys. Rev. Lett. 100, 093602 (2008)

    ADS  Article  Google Scholar 

  15. Hétet, G. et al. Delay of squeezing and entanglement using electromagnetically induced transparency in a vapour cell. Opt. Express 16, 7369–7381 (2008)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  17. Reid, M. D. Demonstration of the Einstein-Podolsky-Rosen paradox using nondegenerate parametric amplification. Phys. Rev. A 40, 913–923 (1989)

    ADS  CAS  Article  Google Scholar 

  18. McCormick, C. F., Marino, A. M., Boyer, V. & Lett, P. D. Strong low-frequency quantum correlations from a four-wave-mixing amplifier. Phys. Rev. A 78, 043816 (2008)

    ADS  Article  Google Scholar 

  19. Boyer, V., Marino, A. M., Pooser, R. C. & Lett, P. D. Entangled images from four-wave mixing. Science 321, 544–547 (2008)

    ADS  CAS  Article  Google Scholar 

  20. 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)

    ADS  CAS  Article  Google Scholar 

  21. Bowen, W. P., Schnabel, R., Lam, P. K. & Ralph, T. C. Experimental characterization of continuous-variable entanglement. Phys. Rev. A 69, 012304 (2004)

    ADS  Article  Google Scholar 

  22. Weedbrook, C., Grosse, N. B., Symul, T., Lam, P. K. & Ralph, T. C. Quantum cloning of continuous-variable entangled states. Phys. Rev. A 77, 052313 (2008)

    ADS  Article  Google Scholar 

  23. Tan, S. M. Confirming entanglement in continuous variable quantum teleportation. Phys. Rev. A 60, 2752–2758 (1999)

    ADS  CAS  Article  Google Scholar 

  24. Grosshans, F. & Grangier, P. Quantum cloning and teleportation criteria for continuous quantum variables. Phys. Rev. A 64, 010301(R) (2001)

    ADS  MathSciNet  Article  Google Scholar 

  25. Boyd, R. W., Gauthier, D. J., Gaeta, A. L. & Willner, A. E. Maximum time delay achievable on propagation through a slow-light medium. Phys. Rev. A 71, 023801 (2005)

    ADS  Article  Google Scholar 

  26. Vudyasetu, P. K., Camacho, R. M. & Howell, J. C. Storage and retrieval of multimode transverse images in hot atomic rubidium vapor. Phys. Rev. Lett. 100, 123903 (2008)

    ADS  Article  Google Scholar 

  27. Shuker, M., Firstenberg, O., Pugatch, R., Ron, A. & Davidson, N. Storing images in warm atomic vapor. Phys. Rev. Lett. 100, 223601 (2008)

    ADS  CAS  Article  Google Scholar 

  28. Boyer, V., Marino, A. M. & Lett, P. D. Generation of spatially broadband twin beams for quantum imaging. Phys. Rev. Lett. 100, 143601 (2008)

    ADS  CAS  Article  Google Scholar 

  29. Collins, O. A., Jenkins, S. D., Kuzmich, A. & Kennedy, T. A. B. Multiplexed memory insensitive quantum repeaters. Phys. Rev. Lett. 98, 060502 (2007)

    ADS  CAS  Article  Google Scholar 

  30. Tordrup, K., Negretti, A. & Molmer, K. Holographic quantum computing. Phys. Rev. Lett. 101, 040501 (2008)

    ADS  MathSciNet  Article  Google Scholar 

Download references


R.C.P. is supported by the Intelligence Community Postdoctoral Program.

Author information

Authors and Affiliations


Corresponding author

Correspondence to A. M. Marino.

Supplementary information

Supplementary Information

This file contains Supplementary Notes, Supplementary Figures 1-2 with Legends and a Supplementary Reference (PDF 198 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Marino, A., Pooser, R., Boyer, V. et al. Tunable delay of Einstein–Podolsky–Rosen entanglement. Nature 457, 859–862 (2009).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing