Exclusive channels in γγ\gamma\gamma reactions: light at the end of the tunnel?

The physics that can be learnt by studying exclusive channels in two photon interactions is recalled. This serves as an introduction to the Exclusive Reaction session of Photon'99.Comment: 9 pages,8 figures. Invited introductory talk at Photon'99, Freiburg im Br., Germany, May 199

Intrinsic Elicitation : A Model and Design Approach for Games Collecting Human Subject Data

Applied games are increasingly used to collect human subject data such as people’s performance or attitudes. Games a ord a motive for data provision that poses a validity threat at the same time: as players enjoy winning the game, they are motivated to provide dishonest data if this holds a strategic in-game advantage. Current work on data collection game design doesn’t address this issue. We therefore propose a theoretical model of why people provide certain data in games, the Rational Game User Model. We derive a design approach for human subject data collection games that we call Intrinsic Elicitation: data collection should be integrated into the game’s mechanics such that honest responding is the necessary, strategically optimal, and least e ortful way to pursue the game’s goal. We illustrate the value of our approach with a sample analysis of the data collection game Urbanology

Magnon-Photon Interactions: From X-ray Mapping of Standing Spin Waves to Interference in Cavity Electromagnonics

This thesis describes two types of light-matter interactions in magnetic thin films. In the first part, it focuses on the resonant interaction of hard X-rays with 57Fe nuclei in a microstructured magnetic element. Specifically, the resonant nuclear scattering from 57Fe nuclei is used to investigate the spatial dependence of magnetization dynamics in a thin, microstructured magnetic stripe. We develop a quasi incoherent scattering model that allows spatial resolution of a standing spin wave profile in this stripe. These results open up new perspectives for depth dependent investigations of laterally varying dynamic spin structures via nuclear resonant scattering.In the second part of this thesis, the focus moves from light as a spatial probe of the magnetization to the interaction of a photonic cavity mode with the Kittel mode of a magnetic thin film. This change of role occurs in the framework of the novel field of cavity electromagnonics, which utilizes a quantum optical model to describe coupled microwave photon-magnon systems. Here, we extend this model to show that a generalized form of Fano interference emerges from the photonic cavity mode interacting with the Kittel mode at low coupling strengths. This is confirmed experimentally by coupling the Kittel mode of a permalloy film to a microwave cavity in the Purcell regime. In addition, we demonstrate that the developed generalized Fano form reveals a coherent contribution representing interference between the magnon and photon channels and an incoherent contribution due to mode coupling. Finally, we show that a Fano phase picture describes well how generalized Fano interference between the magnonic and photonic systems gives way to mode hybridization as the coupling strength increases. These results offer a new perspective on magnon photon coupling and relate the observed reflectivity lineshapes to the quantum optical model of cavity electromagnonics in a physically meaningful way

Connecting Fano interference and the Jaynes-Cummings model in cavity magnonics

We show that Fano interference can be realized in a macroscopic microwave cavity coupled to a spin ensemble at room temperature. Via a formalism developed from the linearized Jaynes-Cummings model of cavity electromagnonics, we show that generalized Fano interference emerges from the photon–magnon interaction at low cooperativity. In this regime, the reflectivity approximates the scattering cross-section derived from the Fano-Anderson model. Although asymmetric lineshapes in this system are often associated with the Fano formalism, we show that whilst Fano interference is actually present, an exact Fano form cannot be achieved from the linear Jaynes-Cummings model. In the Fano model an additional contribution arises, which is attributed to decoherence in other systems, and in this case is due to the resonant nature of the photonic mode. The formalism is experimentally verified and accounts for the asymmetric lineshapes arising from the interaction between magnon and photon channels. As the magnon–photon coupling strength is increased, these channels merge into hybridized magnon–photon modes and the generalized Fano interference picture breaks down. Our results are universally applicable to systems underlying the linearized Jaynes-Cummings Hamiltonian at low cooperativity and connect the microscopic parameters of the quantum optical model to generalized Fano lineshapes

Spectral Control of an X-Ray L -Edge Transition via a Thin-Film Cavity

By embedding a thin layer of tantalum in an x-ray cavity, we observe a change in the spectral characteristics of an inner-shell transition of the metal. The interaction between the cavity mode vacuum and the $L_{III}$-edge transition is enhanced, permitting the observation of the collective Lamb shift, superradiance, and a Fano-like cavity-resonance interference effect. This experiment demonstrates the feasibility of cavity quantum electrodynamics with electronic resonances in the x-ray range with applications to manipulating and probing the electronic structure of condensed matter with high-resolution x-ray spectroscopy in an x-ray cavity setting

Intraspinal lumbar juxtaarticular cyst treatment through CT-guided percutaneus induced rupture results in a favorable patient outcome

Juxta-articular cysts are synovial cysts originating from the facet joints or the flava ligaments. If they grow intra-spinally they can compress nervous structures and cause a variety of symptoms. Micro-neurosurgery is usually the treatment of choice. Alternatively to surgical treatment the cyst can be approached and treated with a CT guided percutaneous injection inducing rupture. After fulfilling strict selection criteria twenty patients (25% of all treated lumbar synovial cyst patients), were treated minimally invasive by this method from 2010-2016. The facet joint was punctured under CT guidance and a mixture of a local anesthetic and contrast liquid was injected until the cyst was blasted. The mean follow-up period was 1.1 years (range 2 weeks - 5 years). Fifteen of twenty procedures were successful and cyst rupture was confirmed by CTscans. Twelve of these fifteen patients experienced a significant improvement of their symptoms and needed no further intervention or surgical procedure up until now, three patients showed no clinical improvement and were treated surgically within one week after cyst rupture. In five patients it was technically not possible to rupture the cyst. These patients were treated microsurgically by cyst resection and dynamic stabilization or fusion procedures. The percutaneus rupture of juxtaarticular cysts has fewer risks and is cost effective compared to microsurgical resection. It may be an alternative to surgical treatment for a selected group of patients. However there are some limitations to the procedure though, such as difficult patient selection, unpredictable outcome or technical problems due to highly degenerated facet joints

Coherent control of collective nuclear quantum states via transient magnons

Ultrafast and precise control of quantum systems at x-ray energies involves photons with oscillation periods below 1 as. Coherent dynamic control of quantum systems at these energies is one of the major challenges in hard x-ray quantum optics. Here, we demonstrate that the phase of a quantum system embedded in a solid can be coherently controlled via a quasi-particle with subattosecond accuracy. In particular, we tune the quantum phase of a collectively excited nuclear state via transient magnons with a precision of 1 zs and a timing stability below 50 ys. These small temporal shifts are monitored interferometrically via quantum beats between different hyperfine-split levels. The experiment demonstrates zeptosecond interferometry and shows that transient quasi-particles enable accurate control of quantum systems embedded in condensed matter environments

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 Fe-57 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