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.

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


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.

Your institute does not have access to this article

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: Illustration of the ZEFOZ transition.
Figure 2: Experimental set-up and pulse sequences.
Figure 3: Two-pulse spin echo decay and illustration of frozen core.
Figure 4: Measured coherence times with CPMG and KDDx pulse sequences.


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

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  3. Briegel, H. J., Dür, W., Circ, J. I. & Zoller, P. Quantum repeaters: the role of imperfect local operations in quantum communication. Phys. Rev. Lett. 81, 5932–5935 (1998)

    ADS  CAS  Article  Google Scholar 

  4. Duan, L. M., Lukin, M. D., Cirac, J. I. & Zoller, P. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001)

    ADS  CAS  Article  Google Scholar 

  5. Sangouard, N., Simon, C., de Riedmatten, H. & Gisin, N. Quantum repeaters based on atomic ensembles and linear optics. Rev. Mod. Phys. 83, 33–80 (2011)

    ADS  Article  Google Scholar 

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

    ADS  MathSciNet  Article  Google Scholar 

  7. Bennett, C. H., Brassard, G., Breidbart, S. & Wiesner, S. in Advances in Cryptology: Proceedings of CRYPTO ’82 (eds Chaum, D., Rivest, R. L. & Sherman, A. T. ) 267–275 (Plenum, 1982)

    Google Scholar 

  8. Longdell, J. J., Fraval, E., Sellars, M. J. & Manson, N. B. Stopped light with storage times greater than one second using electromagnetically induced transparency in a solid. Phys. Rev. Lett. 95, 063601 (2005)

    ADS  CAS  Article  Google Scholar 

  9. Fraval, E., Sellars, M. J. & Longdell, J. J. Dynamic decoherence control of a solid-state nuclear-quadrupole qubit. Phys. Rev. Lett. 95, 030506 (2005)

    ADS  CAS  Article  Google Scholar 

  10. Hedges, M. P., Longdell, J. J., Li, Y. & Sellars, M. J. Efficient quantum memory for light. Nature 465, 1052–1056 (2010)

    ADS  CAS  Article  Google Scholar 

  11. Heinze, G., Hubrich, C. & Halfmann, T. Stopped light and image storage by electromagnetically induced transparency up to the regime of one minute. Phys. Rev. Lett. 111, 033601 (2013)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  14. Timoney, N., Lauritzen, B., Usmani, I., Afzelius, M. & Gisin, N. Atomic frequency comb memory with spin-wave storage in 153Eu3+:Y2SiO5 . J. Phys. B 45, 124001 (2012)

    ADS  Article  Google Scholar 

  15. Thiel, C. W., Böttger, T. & Cone, R. L. Rare-earth-doped materials for applications in quantum information storage and signal processing. J. Lumin. 131, 353–361 (2011)

    CAS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  17. Timoney, N., Usmani, I., Jobez, P., Afzelius, M. & Gisin, N. Single-photon-level optical storage in a solid-state spin-wave memory. Phys. Rev. A 88, 022324 (2013)

    ADS  Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  19. Yano, R., Mitsunaga, M. & Uesugi, N. Ultralong optical dephasing time in Eu3+:Y2SiO5 . Opt. Lett. 16, 1884–1886 (1991)

    ADS  CAS  Article  Google Scholar 

  20. Arcangeli, A., Lovrić, M., Tumino, B., Ferrier, A. & Goldner, P. Spectroscopy and coherence lifetime extension of hyperfine transitions in 153Eu3+:Y2SiO5 . Phys. Rev. B 89, 184305 (2014)

    ADS  Article  Google Scholar 

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

  22. Fraval, E., Sellars, M. J. & Longdell, J. J. Method of extending hyperfine coherence times in Pr3+:Y2SiO5 . Phys. Rev. Lett. 92, 077601 (2004)

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  24. Longdell, J. J., Alexander, A. L. & Sellars, M. J. Characterization of the hyperfine interaction in europium-doped yttrium orthosilicate and europium chloride hexahydrate. Phys. Rev. B 74, 195101 (2006)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  26. Shelby, R. M., Yannoni, C. S. & Macfarlane, R. M. Optically detected coherent transients in nuclear hyperfine levels. Phys. Rev. Lett. 41, 1739–1742 (1978)

    ADS  CAS  Article  Google Scholar 

  27. Thorpe, M. J., Leibrandt, D. R. & Rosenband, T. Shifts of optical frequency references based on spectral-hole burning in Eu3+:Y2SiO5 . New J. Phys. 15, 033006 (2013)

    ADS  Article  Google Scholar 

  28. Souza, A. M., Álvarez, G. A. & Suter, D. Robust dynamical decoupling for quantum computing and quantum memory. Phys. Rev. Lett. 106, 240501 (2011)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  30. Bonarota, M., Le Gouët, J.-L. & Chanelière, T. Highly multimode storage in a crystal. New J. Phys. 13, 013013 (2011)

    ADS  Article  Google Scholar 

Download references


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

Authors and Affiliations



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.

Corresponding author

Correspondence to Manjin Zhong.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Zhong, M., Hedges, M., Ahlefeldt, R. et al. Optically addressable nuclear spins in a solid with a six-hour coherence time. Nature 517, 177–180 (2015).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


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