Many-body Rydberg systems

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Rydberg atoms are highly excited atoms that are sensitive to external fields and other atoms due to their exaggerated properties, which include large polarizabilities and electric-dipole moments. In laser-cooled atom samples, these properties result in strong Rydberg-Rydberg interactions that have been shown to cause a Rydberg excitation blockade. In the blockaded domain, one Rydberg excitation is shared among many atoms, leading to novel quantum many-body states. In this project, the lifetime (decoherence) of these many-body states is probed using echo-type experiments, in which coherent-control techniques are used to reverse excitations via partial or full time reversal of the system evolution. The degree to which a perfect echo can be achieved depends on how well the system evolution can be time-reversed. It is measured how perfect an echo can be achieved by controlling the atomic interactions in a fast, time-dependent manner. Residual deviations from a perfect echo are expected to be indicative of motion-induced de-coherence of the many-body system, which is of high fundamental interest. To explore this topic, the echo visibility is studied as a function of sample parameters such as temperature and duration of the echo sequence. The many-body system this project is dealing with further exhibits spatial correlations between the locations of the Rydberg atoms. These correlations are demonstrated and characterized using a spatially sensitive ion detection method. In related experiments, the dynamics of excitation hopping between atoms is studied. Further merit is provided by the development of a fundamentally new technique for millimeter-wave spectroscopy of Rydberg-Rydberg transitions, based on modulated standing-wave laser fields.The research on de-coherence of many-body Rydberg systems is of high fundamental interest and has implications in quantum information processing. The study of quantum transport in many-body Rydberg systems may further the understanding of the dynamics of electronic excitations in other complex quantum systems, such as biological molecules, light harvesting complexes and nanophotonic materials. Spectroscopy of Rydberg atoms in modulated ponderomotive potentials could have a broader impact on precision measurement of atomic properties and fundamental constants. An important part of the project's impact on society is the training of graduate students in research, oral and written presentation, and teaching. The graduate students are thereby prepared for future responsibilities in academia, government laboratories, and industry. The project includes smaller research components that may be suitable for undergraduate work. Outreach to the general public is provided through the PI's involvement in the University of Michigan Physics Olympiad, the Michigan Math and Science Scholars program, and Science Cafe talks. These activities aim at the encouragement of high-school students to consider a career in science or engineering.