Norman F. Ramsey Prize in Atomic, Molecular and Optical Physics, and in Precision Tests of Fundamental Laws and Symmetries: Quantum Optics with ultra-narrow nuclear transitions*

Narrow optical resonances corresponding to quantum transitions in atoms, molecules,quantum dots, rare-earth ions and color centers constitute the basis of quantum optics with numerous applications in sensing, imaging, computation, communication, etc. Very high-quality atomic resonances with Q-factor ~10 15 -10 20 are on demand for atomic clocks, chronometric geodesy and gravimetry, search for time variation of the fundamental constants and dark matter [1]. Their realization requires low atomic density, vacuum environment, laser cooling below 100 nK temperature, and magnetic traps or optical lattices. Nuclear resonances with similar high-quality factor can be achieved at solid density and even at room temperature, as the nuclei are naturally trapped in a crystal lattice. The major advantage of nuclear vs atomic transitions is a smaller sensitivity to frequency shifts caused by electric and magnetic fields perturbations. Besides, the Mössbauer effect makes it possible to effectively eliminate a thermal-motion broadening. Thus, nuclear transitions offer an appealing platform for a new precision metrology capable, for example, of detecting a gravitational red shift with a sub-mm displacement. They could provide the basis for nuclear clocks [1] and super-dense quantum nuclear memory [2]. However, with the only known exceptions of 229m Th and 235m U, all the nuclear transitions lay in the hard x-ray range. Their resonant excitation, coherent control and interfacing with the resonant x-ray photons is challenging due to absence of the bright coherent sources and high-quality cavities in the hard x-ray range. In this talk we will review recent progress in this field including experimental demonstrations of the coherent waveform shaping of the x-ray photons [3], acoustically induced transparency [4], slow light [5] and very recent realizations of quantum nuclear memory [6] and resonant excitation with a train of x-ray pulses from the European XFEL of the 12.4 keV long-lived (0.46 s) nuclear transition in 45 Sc [7], the most promising Mössbauer nuclear clock candidate.

[1] E. Peik, T. Schumm , M. S. Safronova, A. Pálffy , J. Weitenberg and P. G. Thirolf, Nuclear clocks for

testing fundamental physics, Quantum Sci. Technol. 6 034002 (2021).

[2] X. Zhang, W.-T. Liao, A. A. Kalachev, R.N. Shakhmuratov, M.O. Scully, O. Kocharovskaya, Nuclear

quantum memory and time sequencing of a single γ photon, Phys. Rev. Lett., 123 (25), 250504 (2019).

[3] F. G.Vagizov , V. A. Antonov, Y.V. Radeonychev, R. N. Shakhmuratov, O. Kocharovskaya, Coherent

Control of the Waveforms of Recoilless Gamma-Photons , Nature, 508, 80 (2014).

[4] Y. V. Radeonychev, I. R. Khairulin, F. G. Vagizov, O. Kocharovskaya, Observation of acoustically induced

transparency for gamma –ray photon. Phys. Rev. Lett. 124, 163602 (2020).

[5] I. R. Khairulin, Y.V. Radyonychev, and O. Kocharovskaya, Slowing down xray photons in a vibrating

recoilless resonant absorber, Sci. Rep., 12, 20270 (2022).

[6] S. Velten, L. Bocklage, X. Zhang, K. Schlage, A. Panchwanee, I. Sergeev, O. Leupold, A. I. Chumakov, O.

Kocharovskaya, and R. Röhlsberger ,, Nuclear Frequency Comb for Quantum Memory, to be published.

[7] Yu. Shvyd’ko, R. Röhlsberger, O. Kocharovskaya et al. Resonant excitation of the long-lived 12.4-keV

nuclear state in 45 Sc by x-ray free-electron laser pulses -- towards Mossbauer nuclear clock, to be published.