Chemical as well as physical processes are intrinsically associated with large length and time scales. Thus, an at least partially quantum mechanical description of such a many-body system is analytically only possible in very few exceptional cases. Instead, a statistical mechanical treatment with quantum mechanical methods that can be solved by modern high-performance computers is required. The main task is therefore to devise and implement novel numerical techniques, which are as efficient as possible and yet, at the same time, qualitatively reproduce the correct chemistry and physics of the original system. However, our main focus is not only the development and implementation of novel simulation methods, but also the investigation of scientifically relevant questions of Chemistry, Biophysics and Material Sciences. In particular, we are studying hydrogen-rich systems in condensed phases (liquids, solids and supramolecular systems). Specifically, my research group focuses on studying liquid water, the surface of water and water in confined geometries as well as on biologically relevant reactions in aqueous solutions and on the water surface. In addition, we address hydrogen-rich solids such as ice and metallic hydrogen at very high pressure.