Ab initio approaches to x-ray cavity QED : From multi-mode theory to nonlinear dynamics of Mössbauer nuclei

In this thesis, a theoretical framework for x-ray cavity QED with Mössbauer nuclei is developed. First, it is shown how Jaynes-Cummings-like few-mode models for open resonators can be derived from first principles, which has been an open question in the quantum optics literature. The resulting ab initio few-mode theory is applied to the x-ray cavity case, generalizing a previous phenomenological model. In addition, a second orthogonal approach is developed to enable the numerically efficient treatment of complex cavity geometries. It is shown that one can thereby directly derive a nuclear ensemble Master equation using Green’s functions to encode the cavity environment. This approach provides an ab initio quantum theory for the system, which resolves previous discrepancies and allows to semianalytically calculate cavity-modified nuclear level schemes without the need for a fitting procedure. On the basis of the two developed theories, multi-mode effects resulting from large losses in leaky resonators are investigated. A general criterion is introduced to identify and classify such multi-mode effects, which demonstrates that they are responsible for previously observed signatures in x-ray cavity experiments and can be harnessed to artificially tune nuclear quantum systems. Further interesting cusp features in nuclear Fano interference trajectories of x-ray cavities with overlapping modes are reported. Finally, the gained insights are employed to investigate nonlinear excitation dynamics of Mössbauer nuclei in the presence of strong x-ray driving fields. The feasibility of inverting nuclear ensembles at upcoming facilities and the possibility of using focused pulses in combination with x-ray cavities for intensity boosting is analyzed

Inverse design approach to x-ray quantum optics with Mössbauer nuclei in thin-film cavities

Thin-film cavities containing layers of Mössbauer nuclei have been demonstrated to be a rich platform for x-ray quantum optics. At low excitation, these systems can be described by effective few-level schemes, thereby providing tunable artificial quantum systems at hard x-ray energies. With the recent advent of an ab initio theory, a numerically efficient description of these systems is now possible. On this basis, we introduce the inverse design and develop a comprehensive optimization for an archetype system with a single resonant layer, corresponding to an artificial two-level scheme. We discover a number of qualitative insights into x-ray photonic environments for nuclei that will likely impact the design of future x-ray cavities and thereby improve their performance. The presented methods readily generalize beyond the two-level case and thus provide a clear perspective towards the inverse design of more advanced tunable x-ray quantum optical level schemes

Spectral narrowing of x-ray pulses for precision spectroscopy with nuclear resonances

Spectroscopy of nuclear resonances offers a wide range of applications due to the remarkable energy resolution afforded by their narrow linewidths. However, progress toward higher resolution is inhibited at modern x-ray sources because they deliver only a tiny fraction of the photons on resonance, with the remainder contributing to an off-resonant background. We devised an experimental setup that uses the fast mechanical motion of a resonant target to manipulate the spectrum of a given x-ray pulse and to redistribute off-resonant spectral intensity onto the resonance. As a consequence, the resonant pulse brilliance is increased while the off-resonant background is reduced. Because our method is compatible with existing and upcoming pulsed x-ray sources, we anticipate that this approach will find applications that require ultranarrow x-ray resonances

Reply to: On yoctosecond science

REPLYING TO: Y. Shvyd’ko & P. Schindelmann Nature https://doi.org/10.1038/s41586-022-04870-3 (2022

The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature

Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines