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Optically addressable nuclear spins in a solid with a six-hour coherence time

Nature volume 517, pages 177180 (08 January 2015) | Download Citation


Space-like separation of entangled quantum states is a central concept in fundamental investigations of quantum mechanics and in quantum communication applications. Optical approaches are ubiquitous in the distribution of entanglement because entangled photons are easy to generate and transmit. However, extending this direct distribution beyond a range of a few hundred kilometres1,2 to a worldwide network is prohibited by losses associated with scattering, diffraction and absorption during transmission. A proposal to overcome this range limitation is the quantum repeater protocol3,4, which involves the distribution of entangled pairs of optical modes among many quantum memories stationed along the transmission channel. To be effective, the memories must store the quantum information encoded on the optical modes for times that are long compared to the direct optical transmission time of the channel5. Here we measure a decoherence rate of 8 × 10−5 per second over 100 milliseconds, which is the time required for light transmission on a global scale. The measurements were performed on a ground-state hyperfine transition of europium ion dopants in yttrium orthosilicate (151Eu3+:Y2SiO5) using optically detected nuclear magnetic resonance techniques. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoupling, a coherence time of 370 ± 60 minutes was achieved at 2 kelvin. It has been almost universally assumed that light is the best long-distance carrier for quantum information. However, the coherence time observed here is long enough that nuclear spins travelling at 9 kilometres per hour in a crystal would have a lower decoherence with distance than light in an optical fibre. This enables some very early approaches6,7 to entanglement distribution to be revisited, in particular those in which the spins are transported rather than the light.

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  1. 1.

    et al. Efficient entanglement distribution over 200 kilometers. Opt. Express 17, 11440–11449 (2009)

  2. 2.

    et al. Quantum teleportation and entanglement distribution over 100-kilometre free-space channels. Nature 488, 185–188 (2012)

  3. 3.

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

  4. 4.

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

  5. 5.

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

  6. 6.

    Discussion of experimental proof for the paradox of Einstein, Rosen, and Podolsky. Phys. Rev. 108, 1070–1076 (1957)

  7. 7.

    , , & in Advances in Cryptology: Proceedings of CRYPTO ’82 (eds , & ) 267–275 (Plenum, 1982)

  8. 8.

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

  9. 9.

    , & Dynamic decoherence control of a solid-state nuclear-quadrupole qubit. Phys. Rev. Lett. 95, 030506 (2005)

  10. 10.

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

  11. 11.

    , & Stopped light and image storage by electromagnetically induced transparency up to the regime of one minute. Phys. Rev. Lett. 111, 033601 (2013)

  12. 12.

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

  13. 13.

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

  14. 14.

    , , , & Atomic frequency comb memory with spin-wave storage in 153Eu3+:Y2SiO5. J. Phys. B 45, 124001 (2012)

  15. 15.

    , & Rare-earth-doped materials for applications in quantum information storage and signal processing. J. Lumin. 131, 353–361 (2011)

  16. 16.

    et al. Temperature and concentration dependence of optical dephasing, spectral-hole lifetime, and anisotropic absorption in Eu3+:Y2SiO5. Phys. Rev. B 68, 085109 (2003)

  17. 17.

    , , , & Single-photon-level optical storage in a solid-state spin-wave memory. Phys. Rev. A 88, 022324 (2013)

  18. 18.

    et al. Cavity-enhanced storage in an optical spin-wave memory. New J. Phys. 16, 083005 (2014)

  19. 19.

    , & Ultralong optical dephasing time in Eu3+:Y2SiO5. Opt. Lett. 16, 1884–1886 (1991)

  20. 20.

    , , , & Spectroscopy and coherence lifetime extension of hyperfine transitions in 153Eu3+:Y2SiO5. Phys. Rev. B 89, 184305 (2014)

  21. 21.

    Minimising the Decoherence of Rare Earth Ion Solid State Spin Qubits. Ph.D. thesis, Australian National Univ. (2005)

  22. 22.

    , & Method of extending hyperfine coherence times in Pr3+:Y2SiO5. Phys. Rev. Lett. 92, 077601 (2004)

  23. 23.

    et al. Long-lived qubit memory using atomic ions. Phys. Rev. Lett. 95, 060502 (2005)

  24. 24.

    , & Characterization of the hyperfine interaction in europium-doped yttrium orthosilicate and europium chloride hexahydrate. Phys. Rev. B 74, 195101 (2006)

  25. 25.

    Phase memory in electron spin echoes, lattice relaxation effects in CaWO4:Er, Ce, Mn. Phys. Rev. 168, 370–389 (1968)

  26. 26.

    , & Optically detected coherent transients in nuclear hyperfine levels. Phys. Rev. Lett. 41, 1739–1742 (1978)

  27. 27.

    , & Shifts of optical frequency references based on spectral-hole burning in Eu3+:Y2SiO5. New J. Phys. 15, 033006 (2013)

  28. 28.

    , & Robust dynamical decoupling for quantum computing and quantum memory. Phys. Rev. Lett. 106, 240501 (2011)

  29. 29.

    et al. Room-temperature quantum bit storage exceeding 39 minutes using ionized donors in silicon-28. Science 342, 830–833 (2013)

  30. 30.

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

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We thank N. Manson and S. Rogge for comments on the manuscript. This work was supported by the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (CE110001027), and M.J.S. was supported by an Australian Research Council Future Fellowship (FT110100919). J.J.L. was supported by the Marsden Fund of the Royal Society of New Zealand (contract UOO1221).

Author information


  1. Centre for Quantum Computation and Communication Technology, Laser Physics Centre, The Australian National University, Canberra, Australian Capital Territory 0200, Australia

    • Manjin Zhong
    • , Morgan P. Hedges
    • , Rose L. Ahlefeldt
    • , John G. Bartholomew
    • , Sarah E. Beavan
    • , Sven M. Wittig
    •  & Matthew J. Sellars
  2. Department of Physics, Princeton University, Princeton, New Jersey 08554, USA

    • Morgan P. Hedges
  3. Laboratoire Aimé Cotton, CNRS-UPR 3321, Université Paris-Sud and ENS Cachan, 91405 Orsay, France

    • Rose L. Ahlefeldt
  4. Fakultät für Physik and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 Munich, Germany

    • Sarah E. Beavan
  5. Kayser-Threde GmbH, Wolfratshauser straße 48, 81379 Munich, Germany

    • Sven M. Wittig
  6. The Dodd-Walls Centre for Photonic and Quantum Technologies, and Department of Physics, University of Otago, 730 Cumberland Street, Dunedin 9016, New Zealand

    • Jevon J. Longdell


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The initial project was conceived by M.J.S. and J.J.L. The experimental apparatus and initial experiments were designed and implemented by M.Z. assisted by M.P.H., S.M.W., S.E.B. and M.J.S. The precision alignment of the sample, coherence measurements and yttrium study were performed by M.Z. supported by R.L.A., J.G.B. and M.J.S. Analysis and interpretation of the data was performed by M.Z. and M.J.S. in consultation with R.L.A. and J.G.B. Modelling of the yttrium spin bath and europium hyperfine Hamiltonian was completed by M.Z. with assistance from J.J.L., R.L.A. and M.J.S. The paper was written by M.Z., J.G.B. and M.J.S. in discussion with all remaining authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Manjin Zhong.

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