Rabi oscillations of X-ray radiation between two nuclear ensembles


The realization of the strong coupling regime between a single cavity mode and an electromagnetic resonance is a centrepiece of quantum optics. In this regime, the reversible exchange of a photon between the two components of the system leads to so-called Rabi oscillations. Strong coupling is used in the optical and infrared regimes, for instance, to produce non-classical states of light, enhance optical nonlinearities and control quantum states. Here, we report the first observation of Rabi oscillations of an X-ray photon between two resonant 57Fe layers embedded in two coupled cavities. The system is described by an effective Hamiltonian, in which the two layers couple strongly. We observe sinusoidal beating as the signature of the Rabi oscillations in the system’s temporal evolution, as well as the splitting of nuclear resonances in the reflected light spectrum. Our results significantly advance the development of the new field of X-ray quantum optics.

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Fig. 1: Scheme of the experiment and the quantum optical model
Fig. 2: Measured energy spectra.
Fig. 3: Measurement of Rabi oscillations
Fig. 4: Parameters obtained by the model fit across a range of X-ray incidence angles


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J.H., C.S., L.B. and R.Rö. acknowledge the support of the Helmholtz Association through project-oriented funds. X.K. acknowledges financial support from the China Scholarship Council. X.K. and A.P. are part of and were supported by the DFG Collaborative Research Centre SFB 1225 (ISOQUANT). S.W. acknowledges funding by the Joachim Herz Foundation. The authors thank K. Heeg and J. Evers for helpful discussions.

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X.K. and A.P. proposed the experiment. J.H. and R.Rö. devised the experimental concept and designed the set-up. J.H. and S.W. fabricated the sample. C.S., J.G., L.B., J.H., R.Rü. and R.Rö. performed the experiment. J.H. performed the data analysis. J.H., X.K., A.P. and R.Rö. wrote the paper. All authors participated in discussing the results.

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Correspondence to Adriana Pálffy or Ralf Röhlsberger.

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Haber, J., Kong, X., Strohm, C. et al. Rabi oscillations of X-ray radiation between two nuclear ensembles. Nature Photon 11, 720–725 (2017). https://doi.org/10.1038/s41566-017-0013-3

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