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Laser-induced optical excitation of hydrogen-like alkaline and alkalineearth atoms can be used to create arrays of highly controllable Rydberg states, which are promising candidates for atom-based quantum computation and for realizing new many-body phenomena. In a gas of atoms, the interplay between the laser-drive and strong interactions between Rydberg states yields new cooperative effects, including either the complete blocking or the facilitation of excitations by a nearby Rydberg state. I will discuss theoretical and experimental approaches to the so-called facilitation regime, in which the creation of excitations is conditioned on the presence of a nearby Rydberg state. This gives rise to a kinetically constrained dynamics, supporting the avalanche-like spreading of excitations and a non-equilibrium phase transition into an absorbing state with zero excitations. The interplay of interactions, laserdrive, dissipation and atomic motion, each acting on their individual timescale, gives rise to a multifaceted dynamics. It ranges from an epidemiclike spreading of excitations on an emergent complex network at short times to a long-lived critical regime of repeated scale invariant excitation avalanches, reminiscent of self-organized criticality, at late times.

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Michael Buchhold, Institute for Theoretical Physics, University of Cologne
Seminar Room 0.03, ETP
Contact: Sebastian Diehl