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arXiv:2608.08271

On Demand magnetic-Doppler nuclear frequency comb memory for hard X-ray photons

Yanli Shi, Xiwen Zhang, Yuri Shvyd'ko, Olga Kocharovskaya

quant-phSubmitted Aug 8, 2026• Announced Aug 11, 2026• 0 citations
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Abstract

Nuclear quantum memories in the hard X-ray regime offer some key advantages over their optical counterparts, such as broader bandwidth and lower background noise. A Doppler frequency comb protocol has been theoretically proposed [X. Zhang \textit{et al.}, Phys. Rev. Lett. \textbf{123}, 250504 (2019)] and recently demonstrated experimentally [S. Velten \textit{et al.}, Sci. Adv. \textbf{10}, eadn9825 (2024)] for the storage and retrieval of X-ray photons. However, achieving on-demand retrieval remains challenging because of the requirement for precise and synchronous mechanical motion of multiple absorbers. We propose a hybrid, magnetic-Doppler nuclear frequency comb composed of Doppler-shifted resonant absorbers with lifted nuclear spin degeneracy, which expands the Doppler comb structure. By synchronously reversing the directions of both the magnetic fields and absorber velocities, the system achieves time-reversed phase evolution dynamics that allows for efficient on-demand photon retrieval with significantly reduced mechanical complexity.

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Spectral control over γγγ-ray echo using a nuclear frequency comb system
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We present an extension of the atomic frequency comb protocol that utilizes the Stark effect to perform noisefree, on-demand, control.An experimental realization of this protocol was implemented in the Pr 3+ :Y 2 SiO 5 solid-state system, and a recall efficiency of 38% for a 0.8 μs storage time was achieved.Experiments were performed with both bright pulses as well as weak-coherent states, the latter achieving a signal-to-noise ratio of 570 ± 120 using input pulses with an average photon number of ∼0.1.The principal limitation for a longer storage time was found to be the minimum peak width attainable for Pr 3+ :Y 2 SiO 5 .We employ an adaptation of an established atomic frequency comb model to investigate an on-demand, wide-bandwidth, memory based on Eu 3+ :Y 2 SiO 5 .From this, we determine that a storage time as long as 100 μs may be practical even without recourse to spin-wave storage.
The controllable storage and on demand retrieval of the microwave pulses by using the photon echo quantum memory approach based on a spin frequency comb of inhomogeneous broadening (SFC- protocol) have been demonstrated. We have used an electron-nuclear spin ensemble of tetracyanoethylene anion radicals in toluene which has a natural periodic structure of narrow electron-spin resonance (ESR) hyperfine lines. On-demand retrieval of the stored field has been realized by using two pulses of the magnetic field gradient of an opposite polarity which hold the electron spins in a dephased excited state during the storage time. The obtained experimental results demonstrate promising properties for coherent controlling the electron-nuclear spin ensemble of radicals in liquid that could be useful for implementation of room-temperature broadband quantum memory.
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