Quantum Optics with Ultra-Narrow Gamma Resonances

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Resonance, the strong response of matter to a periodic (oscillating) force in a narrow frequency range (called the "resonance width") in the vicinity of the characteristic frequency of the system (the "resonant frequency"), is a widespread general physical phenomenon. Different types of resonances such as electronic, plasmonic, atomic, and molecular resonances, occur in a wide range of frequencies (from radio frequency to infrared, optical, and ultra-violet), and find numerous applications. For example, they are used to pick up a particular radio station, to generate laser radiation, to detect trace amounts of specific chemical compounds, and to keep a clock ticking at the same rate. Resonance quality factors (defined as the ratio of the resonant frequency to the resonance width) have been achieved as high as 10 to the 17th power (1 followed by 17 zeros) using the electrons inside ultra-cold atoms. By using the atomic nucleus rather than the electrons, researchers funded by this grant are attempting to reach orders of magnitude higher quality factors (such as 10 to the 19th power). These resonances are at x-ray/gamma-ray frequencies rather than at the frequencies corresponding to visible light. Using the nucleus does not require a deep cooling of the atom, and is not limited to small diluted collections of atoms--it can be done in bulk (solid) matter at room temperature. However their investigation is challenging due to the absence of the techniques to produce relatively bright spectrally narrow x-ray/gamma-ray radiation and to control its interaction with the nucleus. This project aims at the development of such techniques and at the demonstration, exploration and applications of the ultra-narrow nuclear gamma-ray resonances. Its successful realization would give strong impetus to the development of quantum nuclear metrologies and technologies, from nuclear clocks to super-resolution nuclear spectrometers, from spectrally enhanced quasi-monochromatic x-ray sources to compact long-lived nuclear quantum memories with potential applications in high-precision tests of fundamental physics, quantum information science, chemistry, biology, medicine, and material nanoscience. The graduate and undergraduate students will be trained in this emerging highly interdisciplinary research field on the borderlines between quantum and x-ray optics by learning the experimental techniques, analytical methods, and numerical modeling. The project consists of two parts. The first one aims at the development of the techniques for coherent control of the spectral content and temporal shape of x-ray radiation via its resonant interaction with nuclear targets. It includes the demonstration of i) slow single gamma-photons propagating through matter with an effective speed of ~30m/s, ii) transparency for the bichromatic gamma-ray photons, iii) quantum nuclear memories, and iv) spectral intensity enhancement of gamma-ray photons. The experiments will be based on the recent theoretical proposals and experimental achievements of the supported research group (X. Zhang et al. Phys. Rev. Lett. 123, 250504 (2019); Y. V. Radeonychev, et al. Phys. Rev. Lett. 124, 163602 (2020)) and performed in the researchers lab at Texas A&M University using a 14.4 keV transition of Iron-57 nuclei with 1.1 MHz radiative line broadening excited with the heralded radioactive source of Cobalt-57. The second part of the project aims at demonstrating the ultra-narrow (0.17Hz) resonance at 12.4 keV for a nuclear transition in Scandium-45. These experiments will be performed at the European XFEL, currently the brightest source of hard x-ray radiation in the range of 10-25 keV photons, while the fabrication and preliminary testing of the required monochromators and beam splitters will be done by the co-PI’s group at the Argonne National Laboratiory.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.