Two of the grand challenges of modern science concern: (I) extending our quantitative understanding of matter to out-of-equilibrium scenarios, and (ii) uncovering general laws governing how complex non-equilibrium phenomena emerge from underlying physical principles. In fact, most physical systems found in nature are not in thermodynamic equilibrium, as, for instance, their inevitable coupling to the environment can give rise to fundamentally new behaviour. Understanding open quantum many-body systems poses a significant challenge, since theoretical methods capable of dealing with such scenarios are less developed and it is experimentally difficult to devise observables capable of distinguishing their vastly different types of behaviour.

We experimentally investigate the dynamics and phase structure of an open quantum systems consisting of clouds of ultracold atoms laser-excited from the ground state to a Rydberg state. The strong interplay between coherent driving, dissipation and interactions gives rise to wide variety of new phenomena.

**More details about our research can be found in the following papers**

### Diffusive to non-ergodic dipolar transport in a dissipative atomic medium

We highlight a well controlled experimental system for studying transport phenomena consisting of strongly interacting impurities in a Rydberg-dressed ultracold gas, which due to its long-range 1/R^3 hopping and controllable…

### Uncovering the nonequilibrium phase structure of an open quantum spin system, in Phys. Rev. A

We experimentally and theoretically investigate the nonequilibrium phase structure of a well-controlled driven-dissipative quantum spin system governed by the interplay of coherent driving, spontaneous decay, and long-range spin-spin interactions. Statistical…

### Observation of Self Organised Criticality in an Ultracold Atomic Gas

We present the experimental observation of self-organised criticality in the dynamics of a driven-dissipative gas of ultracold atoms and a first characterisation of its universal properties. Self organisation provides an…

### Relaxation of an isolated dipolar-interacting Rydberg quantum spin system, in Phys. Rev. Lett.

How do isolated quantum systems approach an equilibrium state? In collaboration with Prof. Matthias Weidemüller (Physics Institute, University of Heidelberg) and Prof. Jürgen Berges (Institute for theoretical physics, University of…

### Full Counting Statistics of Laser Excited Rydberg Aggregates in a One-Dimensional Geometry, in Phys. Rev. Lett.

Full Counting Statistics (FCS) can provide valuable information on manybody systems especially if the underlying correlations cannot be directly imaged. We have used the FCS of Rydberg excitations to gain…

### Sub-Poissonian statistics of Rydberg-interacting dark-state polaritons, in Phys. Rev. Lett.

Electromagnetically-induced transparency (EIT) and the associated appearance of hybrid quasi-particles (dark-state polaritons) in ultracold Rydberg gases have opened intriguing perspectives to create new atom-light interfaces operating at the quantum level…

### Spontaneous avalanche ionization of a strongly blockaded Rydberg gas, in Phys. Rev. Lett.

We have observed the sudden and spontaneous evolution of an initially correlated gas of repulsively interacting Rydberg atoms to an ultracold plasma. By combining optical imaging and ion detection, we…