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Strong coupling of alkali-metal spins to noble-gas spins with an hour-long coherence time


Nuclear spins of noble gases can maintain coherence for hours at ambient conditions because they are isolated by complete electron shells1. This isolation, however, impedes the ability to manipulate and control them by optical means or by coupling to other spin gases2,3,4. Here we achieve strong coherent coupling between noble-gas spins and the optically accessible spins of an alkali-metal vapour. The coupling emerges from the coherent accumulation of stochastic spin-exchange collisions. We obtain a coupling strength ten times higher than the decay rate, observe the coherent and periodic exchange of spin excitations between the two gases and demonstrate active control over the coupling by an external magnetic field. This approach could be developed into a fast and efficient interface for noble-gas spins, enabling applications in quantum sensing and information5,6.

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Fig. 1: Experimental scheme and coherence time measurements.
Fig. 2: Exchange of collective spin excitations.
Fig. 3: Measured dynamics of the coupled alkali-metal–noble-gas spin system in three regimes.
Fig. 4: Spectral response of the alkali-metal–noble-gas spin system in the strong-coupling regime.

Data availability

All data needed to evaluate the conclusions in the paper are present in the paper. The data that support the findings of this study and additional data are available from the corresponding author upon request.


  1. Gentile, T. R., Nacher, P. J., Saam, B. & Walker, T. G. Optically polarized 3He. Rev. Mod. Phys. 89, 045004 (2017).

    ADS  Article  Google Scholar 

  2. Walker, T. G. & Larsen, M. S. Spin-exchange-pumped NMR gyros. Adv. Atom. Mol. Opt. Phys. 65, 373 (2016).

  3. Kornack, T. W. & Romalis, M. V. Dynamics of two overlapping spin ensembles interacting by spin exchange. Phys. Rev. Lett. 89, 253002 (2002).

    ADS  Article  Google Scholar 

  4. Jimenez-Martinez, R. et al. Optical hyperpolarization and NMR detection of 129Xe on a microfluidic chip. Nat. Commun. 5, 3908 (2014).

    ADS  Article  Google Scholar 

  5. Katz.O., Shaham, R., Polzik, E. S. & Firstenberg, O. Long-lived entanglement generation of nuclear spins using coherent light. Phys. Rev. Lett. 124, 043602 (2020).

  6. Katz, O., Reches, E., Shaham, R., Gorshkov, A. V. & Firstenberg, O. Optical quantum memory with optically inaccessible noble-gas spins. Preprint at (2020).

  7. Heil, W. et al. Spin clocks: probing fundamental symmetries in nature. Ann. Phys. 525, 539–549 (2013).

    Article  Google Scholar 

  8. Gemmel, C. et al. Ultra-sensitive magnetometry based on free precession of nuclear spins. Eur. Phys. J. D 57, 303–320 (2010).

    ADS  Article  Google Scholar 

  9. Kornack, T. W., Ghosh, R. K. & Romalis, M. V. Nuclear spin gyroscope based on an atomic comagnetometer. Phys. Rev. Lett. 95, 230801 (2005).

    ADS  Article  Google Scholar 

  10. Thrasher, D. A. et al. Continuous comagnetometry using transversely polarized Xe isotopes. Phys. Rev. A 100, 061403 (2019).

    ADS  Article  Google Scholar 

  11. Kitching, J. Chip-scale atomic devices. Appl. Phys. Rev. 5, 031302 (2018).

    ADS  Article  Google Scholar 

  12. Chupp, T. & Swanson, S. Medical imaging with laser-polarized noble gases. Adv. Atom. Mol. Opt. Phys. 45, 41–98 (2001).

    ADS  Article  Google Scholar 

  13. Brown, J. M., Smullin, S. J., Kornack, T. W. & Romalis, M. V. New limit on Lorentz- and CPT-violating neutron spin interactions. Phys. Rev. Lett. 105, 151604 (2010).

    ADS  Article  Google Scholar 

  14. Jackson Kimball, D. F., Boyd, A. & Budker, D. Constraints on anomalous spin–spin interactions from spin-exchange collisions. Phys. Rev. A 82, 062714 (2010).

    ADS  Article  Google Scholar 

  15. Alonso, R., Blas, D. & Wolf, P. Exploring the ultra-light to sub-MeV dark matter window with atomic clocks and co-magnetometers. J. High Energy Phys. 2019, 69 (2019).

    Article  Google Scholar 

  16. Bloch, I. M., Hochberg, Y., Kuflik, E. & Volansky, T. Axion-like relics: new constraints from old comagnetometer data. J. High Energy Phys. 2020, 167 (2020).

    Article  Google Scholar 

  17. Chupp, T. E., Fierlinger, P., Ramsey-Musolf, M. J. & Singh, J. T. Electric dipole moments of atoms, molecules, nuclei, and particles. Rev. Mod. Phys. 91, 015001 (2019).

    ADS  MathSciNet  Article  Google Scholar 

  18. Katz, O., Shaham, R., Reches, E., Gorshkov, A. V. & Firstenberg, O. Optimal control of an optical quantum memory based on noble-gas spins. Preprint at (2020).

  19. Dantan, A. et al. Long-lived quantum memory with nuclear atomic spins. Phys. Rev. Lett. 95, 123002 (2005).

  20. Serafin, A., Fadel, M., Treutlein, P. & Sinatra, A. Nuclear spin squeezing in helium-3 by continuous quantum nondemolition measurement. Phys. Rev. Lett. 127, 013601 (2021).

    ADS  Article  Google Scholar 

  21. Serafin, A., Castin, Y., Fadel, M., Treutlein, P. & Sinatra, A. Étude théorique de la compression de spin nucléaire par mesure quantique non destructive en continu. C. R. Phys. 22, 1–35 (2021).

    Google Scholar 

  22. Katz, O., Shaham, R. & Firstenberg, O. Quantum interface for noble-gas spins. PRX Quantum 3, 010305 (2022).

  23. Hammerer, K., Sorensen, A. S. & Polzik, E. S. Quantum interface between light and atomic ensembles. Rev. Mod. Phys. 82, 1041–1093 (2010).

    ADS  Article  Google Scholar 

  24. Shaham, R., Katz, O. & Firstenberg, O. Quantum dynamics of collective spin states in a thermal gas. Phys. Rev. A 102, 012822 (2020).

    ADS  MathSciNet  Article  Google Scholar 

  25. Sun, J. et al. Spatial multiplexing of squeezed light by coherence diffusion. Phys. Rev. Lett. 123, 203604 (2019).

    ADS  Article  Google Scholar 

  26. Dellis, A. T., Loulakis, M. & Kominis, I. K. Spin-noise correlations and spin-noise exchange driven by low-field spin-exchange collisions. Phys. Rev. A 90, 032705 (2014).

    ADS  Article  Google Scholar 

  27. Kong, J. Measurement-induced, spatially-extended entanglement in a hot, strongly-interacting atomic system. Nat. Commun. 11, 2415 (2020).

    ADS  Article  Google Scholar 

  28. Mouloudakis, K. & Kominis, I. K. Spin-exchange collisions in hot vapors creating and sustaining bipartite entanglement. Phys. Rev. A 103, L010401 (2021).

    ADS  Article  Google Scholar 

  29. Sherson, J. F. et al. Quantum teleportation between light and matter. Nature 443, 557–560 (2006).

    ADS  Article  Google Scholar 

  30. Gorshkov, A. V., Andre, A., Fleischhauer, M., Sorensen, A. S. & Lukin, M. D. Universal approach to optimal photon storage in atomic media. Phys. Rev. Lett. 98, 123601 (2007).

    ADS  Article  Google Scholar 

  31. Firstenberg, O. et al. Self-similar modes of coherent diffusion. Phys. Rev. Lett. 105, 183602 (2010).

    ADS  Article  Google Scholar 

  32. Appelt, S. et al. Theory of spin-exchange optical pumping of 3He and 129Xe. Phys. Rev. A 58, 1412–1439 (1998).

    ADS  Article  Google Scholar 

  33. Batz, M., Nacher, P. J. & Tastevin, G. Fundamentals of metastability exchange optical pumping in helium. J. Phys. Conf. Ser. 294, 012002 (2011).

  34. Walter, D. K., Happer, W. & Walker, T. G. Estimates of the relative magnitudes of the isotropic and anisotropic magnetic-dipole hyperfine interactions in alkali-metal-noble-gas systems. Phys. Rev. A 58, 3642–3653 (1998).

    ADS  Article  Google Scholar 

  35. Katz, O., Shaham, R. & Firstenberg, O. Coupling light to a nuclear spin gas with a two-photon linewidth of five millihertz. Sci. Adv. 7, eabe9164 (2021).

  36. Chen, W. C., Gentile, T. R., Ye, Q., Walker, T. G. & Babcock, E. On the limits of spin-exchange optical pumping of 3He. J. Appl. Phys. 116, 014903 (2014).

  37. Allred, J. C., Lyman, R. N., Kornack, T. W. & Romalis, M. V. High-sensitivity atomic magnetometer unaffected by spin-exchange relaxation. Phys. Rev. Lett. 89, 130801 (2002).

    ADS  Article  Google Scholar 

  38. Walker, T. G. & Happer, W. Spin-exchange optical pumping of noble-gas nuclei. Reviews of Modern Physics 69, 629–642 (1997).

    ADS  Article  Google Scholar 

  39. Vasilakis, G., Shah, V. & Romalis, M. V. Stroboscopic Backaction Evasion in a Dense Alkali-Metal Vapor. Physical Review Letters 106, 143601 (2011).

    ADS  Article  Google Scholar 

  40. W. Happer, Y.-Y. Jau, and T.Walker, Optically Pumped Atoms ISBN 978-3-527-40707-1 (WILEY-VCH, 2010)

  41. Happer, W. & Tam, A. C. Effect of rapid spin exchange on the magnetic-resonance spectrum of alkali vapors. Physical Review A 16, 1877–1891 (1977).

    ADS  Article  Google Scholar 

  42. Romalis, M. V., Sheng, D., Saam, B. & Walker, T. G. Comment on “New Limit on Lorentz-Invariance- and C P T -Violating Neutron Spin Interactions Using a Free-Spin-Precession 3He -129Xe Comagnetometer”. Physical Review Letters 113, 188901 (2014).

    ADS  Article  Google Scholar 

  43. Katz, O., Peleg, O. & Firstenberg, O. Coherent Coupling of Alkali Atoms by Random Collisions. Physical Review Letters 115, 113003 (2015).

    ADS  Article  Google Scholar 

  44. Duan, L.-M., Cirac, J. I., Zoller, P. & Polzik, E. S. Quantum Communication between Atomic Ensembles Using Coherent Light. Physical Review Letters 85, 5643–5646 (2000).

    ADS  Article  Google Scholar 

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We thank C. Avinadav and R. Finkelstein for fruitful discussions. We acknowledge financial support by the Israel Science Foundation, the European Research Council starting investigator grant Q-PHOTONICS 678674, the Minerva Foundation with funding from the Federal German Ministry for Education and Research and the Laboratory in Memory of Leon and Blacky Broder.

Author information

Authors and Affiliations



R.S., O.K. and O.F. all contributed to the experimental design, construction, data collection and analysis of this experiment. R.S. claims responsibility for all figures. The authors wrote the manuscript together.

Corresponding author

Correspondence to R. Shaham.

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Extended data

Extended Data Fig. 1 Spin-exchange optical pumping.

Typical measurement of the pumping process of helium-3 by optically pumped potassium vapor. Here the potassium density is na = 4.9  1014 cm−3, and the helium depolarization time is \({T}_{1,{{{\rm{act}}}}}^{{{{\rm{b}}}}}=3.9\) h.

Source data

Extended Data Fig. 2 Variables extracted from fitting Eq. (3) to the measured signals for each exchange time t, as exemplified in Extended Data Fig. 3.

a. The change in alkali precession frequency ωa(t, τ = 0) [see Eq. (2)] manifests the change in the slowing-down factor due to alkali depolarization. b. The degree of alkali polarization pa(t) (in semi-log scale). In a and b, dashed black line correspond to the fitted multi-exponential model, and dotted lines present its confidence bounds. These are used as uncertainty estimations when using pa(t) to scale \(\langle \hat{a}\rangle\) and \(\langle \hat{b}\rangle\). Less reliable data, extracted when the excitations reside predominantly in the noblegas spins, are marked in gray. c. The two frequency components (amplitude squared) of the normalized Faraday rotation signal \({\overline{S}}_{x}(t+\tau )\). Note the factor of (Δ/J)2 100 between them. Each data-point is averaged over 12 to 20 repetitions of the sequence.

Source data

Extended Data Fig. 3 Pulse sequence and typical results of an excitation-exchange measurement.

a. First, we turn off the pumping and bring the two species to strong coupling with a small detuning Δ. We then generate a transverse excitation with a transverse magnetic field pulse. At a later time t, we halt the exchange by increasing the axial magnetic field and setting a large Δ. b. Example of a measured signal with exchange duration t = 11 ms, with Δ = − 1.15J before t, and Δ = 790 Hz J after t. We measure the alkali electron spin (red) which, once Δ is increased, can be used as a magnetometer that senses the noble-gas spin. The fast oscillations of the signal correspond to the Larmor precession of the alkali spin, and the slow modulation corresponds to the noble-gas precession. The latter is highlighted by the blue line (generated by low-pass filtering of the signal for illustrative purposes). We fit the signal to the model from Eq. (3) (dashed black line) and find the amplitudes of the alkali and noble-gas components at time t, which are used to estimate \(\langle \hat{a}(t)\rangle\) and \(\langle \hat{b}(t)\rangle\), respectively. The same fit also provides pa(t).

Source data

Supplementary information

Supplementary Information

Supplementary Sections 1 and 2, and reference.

Source data

Source Data Fig. 1

Contains the data presented in Fig. 1b (measurement of noble-gas coherence time).

Source Data Fig. 2

Contains the data presented in Fig. 2. Sheet labelled ‘exp’ contains the measured data points and error bars; coloured error bars, denoting measurements uncertainty and scattering, are presented in ‘dNa’\‘dNb’ columns, while grey error bars, denoting uncertainty in the data interpretation\scaling, are presented in ‘eNa+\-’,‘eNb+\-’ columns. Sheet labelled ‘model’ contains the data of the model presented on top of measurements (Fig. 2, solid lines).

Source Data Fig. 3

Contains the data presented in Fig. 3. Sheet ‘strong coupling’ contains the data in Fig. 3a. Sheet ‘detuned’ contains the data presented in Fig. 3b. Sheet ‘overdamped’ contains the data presented in Fig. 3c (solid and dashed lines).

Source Data Fig. 4

Contains the data presented in Fig. 4. All spectrum data (sheets ‘spectrum_exp’, ‘spectrum_model’ and ‘spectrum_imperfect_model’) appear such that the first row contains the ‘Delta/J’ values, the first column contains the ‘omega/J’ values and the rest of the table contains the normalized Fourier amplitudes presented in the figure. Sheet ‘spectrum_exp’ contains the data of Fig. 4a. Sheet ‘spectrum_model’ contains the data of Fig. 4b. Sheet ‘spectrum_imperfect_model’ contains the data of Fig. 4c. Sheet ‘eigenfrequencies’ contains the data of the dashed white lines in Fig. 4a.

Source Data Extended Data Fig. 1

Contains the data presented in Extended Data Fig. 1.

Source Data Extended Data Fig. 2

Contains the data presented in Extended Data Fig. 2. Sheet ‘alkali decoupling frequency’ contains the data in Extended Data Fig. 2a. ‘omega’ versus ‘t’ is the measured data, with ‘domega’ being the error bars (red and grey circles), and ‘omega_model’ versus ‘t_model’ is the fitted model (dashed black line) with ‘domega_model+\-’ being the upper\lower confidence bounds of the model (respectively). Sheet ‘alkali polarization’ contains the data in Extended Data Fig. 2b. Again, ‘p_a’ versus ‘t’ is the measured data, with ‘dp_a’ being the errorbars (red and grey circles), and ‘p_model’ versus ‘t_model’ is the fitted model (dashed black line) with ‘dp_model+\-’ being the upper\lower confidence bounds of the model (respectively). Sheet ‘fitting amplitudes’ contains the data in Extended Data Fig. 2c, where ‘dNa\b’ are the errorbars.

Source Data Extended Data Fig. 3

Contains the data presented in Extended Data Fig. 3b, as follows; ‘sx’ versus ‘t’ is the measured data (red line), ‘ky’ versus ‘t for ky’ is the low-pass-filtered data (blue line) and ‘model’ versus ‘t for model’ is the fitted model (dashed black line).

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Shaham, R., Katz, O. & Firstenberg, O. Strong coupling of alkali-metal spins to noble-gas spins with an hour-long coherence time. Nat. Phys. 18, 506–510 (2022).

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