Department of Physics • University of Cologne

Laser-induced optical excitation of hydrogen-like alkaline and alkaline-earth 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, laser-drive, dissipation and atomic motion, each acting on their individual time-scale, gives rise to a multifaceted dynamics. It ranges from an epidemic-like 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.