Electromagnetically induced transparency of ultralong-range Rydberg molecules

We study the impact of Rydberg molecule formation on the storage and retrieval of Rydberg polaritons in an ultracold atomic medium. We observe coherent revivals appearing in the retrieval efficiency of stored photons that originate from simultaneous excitation of Rydberg atoms and Rydberg molecules in the system with subsequent interference between the possible storage paths. We show that over a large range of principal quantum numbers the observed results can be described by a two-state model including only the atomic Rydberg state and the Rydberg dimer molecule state. At higher principal quantum numbers the influence of polyatomic molecules becomes relevant and the dynamics of the system undergoes a transition from coherent evolution of a few-state system to an effective dephasing into a continuum of molecular states.Comment: Submitted to PR

Free-Space Quantum Electrodynamics with a single Rydberg superatom

The interaction of a single photon with an individual two-level system is the textbook example of quantum electrodynamics. Achieving strong coupling in this system so far required confinement of the light field inside resonators or waveguides. Here, we demonstrate strong coherent coupling between a single Rydberg superatom, consisting of thousands of atoms behaving as a single two-level system due to the Rydberg blockade, and a propagating light pulse containing only a few photons. The strong light-matter coupling in combination with the direct access to the outgoing field allows us to observe for the first time the effect of the interactions on the driving field at the single photon level. We find that all our results are in quantitative agreement with the predictions of the theory of a single two-level system strongly coupled to a single quantized propagating light mode. The demonstrated coupling strength opens the way towards interfacing photonic and atomic qubits and preparation of propagating non-classical states of light, two crucial building blocks in future quantum networks

Transient Density-Induced Dipolar Interactions in a Thin Vapor Cell

We exploit the effect of light-induced atomic desorption to produce high atomic densities (n ≫ k3) in a rubidium vapor cell. An intense off-resonant laser is pulsed for roughly one nanosecond on a micrometersized sapphire-coated cell, which results in the desorption of atomic clouds from both internal surfaces. We probe the transient atomic density evolution by time-resolved absorption spectroscopy. With a temporal resolution of ≈ 1 ns, we measure the broadening and line shift of the atomic resonances. Both broadening and line shift are attributed to dipole-dipole interactions. This fast switching of the atomic density and dipolar interactions could be the basis for future quantum devices based on the excitation blockade

Economic Effects of Recent Social and Technological Developments

This paper summarizes and connects the main findings of the habilitation project. The important social developments analyzed, result from the demographic change that many economies will face in the future. Especially on the regional level, problems arise due to increasing disparities in population. This challenges the comprehensive pro-vision of public services such as health care or basic infrastructure. Therefore, new strategies have to be implemented and previous structures have to be adapted. In particular, as also many cities, which have always been agglomeration areas of economic activity, face demographic and/or economic problems, appropriate proactive strategies must be developed to ensure future prosperity. The most predominant recent technological development is the emergence and comprehensive availability of the Internet. This has led to new business opportunities but also new threats for economic activity. One particular online market comprises online games. In this market, due to the virtuality on the one hand and the importance of net-work externalities on the other hand, challenges for the assignment of property rights of virtual objects and optimal pricing strategies arise that have to considered. In the context of B2B, and also B2C, cloud computing becomes more and more important, however, this service is threatened by cybercriminals that force access into the cloud. Thus, the provider must develop strategies to prevent damage for his customers and the economy. All in all, overall analysis shows that only cooperation of all relevant (economic) stakeholders can help to overcome challenges of social and technological developments

Optimal Control and Spatial Heterogeneity: Pattern Formation in Economic-Ecological Models

This paper extends Turing analysis to standard recursive optimal control frameworks in economics and applies it to dynamic bioeconomic problems where the interaction of coupled economic and ecological dynamics under optimal control over space creates (or destroys) spatial heterogeneity. We show how our approach reduces the analysis to a tractable extension of linearization methods applied to the spatial analog of the well known costate/state dynamics. We explicitly show the existence of a non-empty Turing space of diffusive instability by developing a linear-quadratic approximation of the original non-linear problem. We apply our method to a bioeconomic problem, but the method has more general economic applications where spatial considerations and pattern formation are important. We believe that the extension of Turing analysis and the theory associated with the dispersion relationship to recursive infinite horizon optimal control settings is new