Letter | Published:

Heralded quantum entanglement between two crystals

Nature Photonics volume 6, pages 234237 (2012) | Download Citation

Abstract

Quantum networks must have the crucial ability to entangle quantum nodes1. A prominent example is the quantum repeater2,3,4, which allows the distance barrier of direct transmission of single photons to be overcome, provided remote quantum memories can be entangled in a heralded fashion. Here, we report the observation of heralded entanglement between two ensembles of rare-earth ions doped into separate crystals. A heralded single photon is sent through a 50/50 beamsplitter, creating a single-photon entangled state delocalized between two spatial modes. The quantum state of each mode is subsequently mapped onto a crystal, leading to an entangled state consisting of a single collective excitation delocalized between two crystals. This entanglement is revealed by mapping it back to optical modes and by estimating the concurrence of the retrieved light state5. Our results highlight the potential of crystals doped with rare-earth ions for entangled quantum nodes and bring quantum networks based on solid-state resources one step closer.

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References

  1. 1.

    The quantum internet. Nature 453, 1023–1030 (2008).

  2. 2.

    , , & Quantum repeaters: the role of imperfect local operations in quantum communication. Phys. Rev. Lett. 81, 5932–5935 (1998).

  3. 3.

    , , & Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001).

  4. 4.

    , , & Quantum repeaters based on atomic ensembles and linear optics. Rev. Mod. Phys. 83, 33–80 (2011).

  5. 5.

    et al. Measurement-induced entanglement for excitation stored in remote atomic ensembles. Nature 438, 828–832 (2005).

  6. 6.

    & Quantum communication. Nature Photon. 1, 165–171 (2007).

  7. 7.

    , & Quantum-enhanced measurements: beating the standard quantum limit. Science 306, 1330–1336 (2004).

  8. 8.

    & Quantum Computation and Quantum Information (Cambridge Univ. Press, 2000).

  9. 9.

    et al. Linear optical quantum computing with photonic qubits. Rev. Mod. Phys. 79, 135–174 (2007).

  10. 10.

    , , & Quantum cryptography. Rev. Mod. Phys. 74, 145–195 (2002).

  11. 11.

    , & Experimental long-lived entanglement of two macroscopic objects. Nature 413, 400–403 (2001).

  12. 12.

    , , & Single-photon bus connecting spin-wave quantum memories. Nature Phys. 3, 765–769 (2007).

  13. 13.

    , , , & Heralded entanglement between atomic ensembles: preparation, decoherence, and scaling. Phys. Rev. Lett. 99, 180504 (2007).

  14. 14.

    , , & Mapping photonic entanglement into and out of a quantum memory. Nature 452, 67–71 (2008).

  15. 15.

    et al. Functional quantum nodes for entanglement distribution over scalable quantum networks. Science 316, 1316–1320 (2007).

  16. 16.

    et al. Experimental demonstration of a BDCZ quantum repeater node. Nature 454, 1098–1101 (2008).

  17. 17.

    et al. Entanglement of single-atom quantum bits at a distance. Nature 449, 68–71 (2007).

  18. 18.

    et al. Photon-echo quantum memory in solid state systems. Laser Photon. Rev. 4, 244–267 (2010).

  19. 19.

    , , & Stopped light with storage times greater than one second using electromagnetically induced transparency in a solid. Phys. Rev. Lett. 95, 063601 (2005).

  20. 20.

    , , & Efficient quantum memory for light. Nature 465, 1052–1056 (2010).

  21. 21.

    , , & Mapping multiple photonic qubits into and out of one solid-state atomic ensemble. Nature Commun. 1, 12 (2010).

  22. 22.

    , & Highly multimode storage in a crystal. New J. Phys. 13, 013013 (2011).

  23. 23.

    et al. Quantum storage of photonic entanglement in a crystal. Nature 469, 508–511 (2011).

  24. 24.

    et al. Broadband waveguide quantum memory for entangled photons. Nature 469, 512–515 (2011).

  25. 25.

    et al. Quantum repeaters with photon pair sources and multimode memories. Phys. Rev. Lett. 98, 190503 (2007).

  26. 26.

    Single-particle entanglement. Phys. Rev. A 72, 064306 (2005).

  27. 27.

    , , & Multimode quantum memory based on atomic frequency combs. Phys. Rev. A 79, 052329 (2009).

  28. 28.

    , , , & A solid-state light–matter interface at the single-photon level. Nature 456, 773–777 (2008).

  29. 29.

    et al. Demonstration of atomic frequency comb memory for light with spin-wave storage. Phys. Rev. Lett. 104, 040503 (2010).

  30. 30.

    et al. Storage and recall of weak coherent optical pulses with an efficiency of 25%. Phys. Rev. Lett. 105, 060501 (2010).

  31. 31.

    , , & Efficiency optimization for atomic frequency comb storage. Phys. Rev. A 81, 033803 (2010).

  32. 32.

    & Impedance-matched cavity quantum memory. Phys. Rev. A 82, 022310 (2010).

  33. 33.

    , & Efficient multimode quantum memory based on photon echo in an optimal QED cavity. Phys. Rev. A 82, 022311 (2010).

  34. 34.

    , & Optical state truncation by projection synthesis. Phys. Rev. Lett. 81, 1604–1606 (1998).

  35. 35.

    et al. Purification of single-photon entanglement. Phys. Rev. Lett. 104, 180504 (2010).

  36. 36.

    et al. Long-distance entanglement distribution with single-photon sources. Phys. Rev. A 76, 050301 (R) (2007).

  37. 37.

    et al. Waveguide-based OPO source of entangled photon pairs. New J. Phys. 11, 113042 (2009).

  38. 38.

    et al. Ultrafast superconducting single-photon detectors for near-infrared-wavelength quantum communications. J. Mod. Opt. 51, 1447–1458 (2004).

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Acknowledgements

The authors thank H. de Riedmatten, P. Sekatski and J. Laurat for stimulating discussions, and A. Korneev for help with the superconducting detector. This work was supported by the Swiss National Centres of Competence in Research (NCCR) project ‘Quantum Science Technology (QSIT)’, the Science and Technology Cooperation Program Switzerland–Russia, the European Union FP7 project 247743 ‘Quantum repeaters for long distance fibre-based quantum communication (QUREP)’ and the European Research Council Advanced Grant ‘Quantum correlations (QORE)’. F.B. was supported in part by le Fond Québécois de la Recherche sur la Nature et les Technologies.

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Affiliations

  1. Group of Applied Physics, University of Geneva, CH-1211 Geneva 4, Switzerland

    • Imam Usmani
    • , Christoph Clausen
    • , Félix Bussières
    • , Nicolas Sangouard
    • , Mikael Afzelius
    •  & Nicolas Gisin

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Contributions

All authors conceived the experiment. I.U., C.C. and F.B. performed the measurements. I.U., C.C., F.B., N.S. and M.A. analysed the data. All authors contributed to the writing of the manuscript. I.U., C.C. and F.B. contributed equally to this work.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Mikael Afzelius.

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DOI

https://doi.org/10.1038/nphoton.2012.34

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