To describe nanoscale devices at very small temperatures or to understand the low temperature behavior of solids, gases and liquids, one necessarily has to employ quantum field theoretical methods. The Theoretical Physics Department hosts currently two independent "Momentum" research groups, focusing on quantum statistical physics, integrable systems, and interacting cold atoms, and transport in nanostructures. In addition, we also carry out intense research in the field of quantum information theory and its application in ab initio calculations, and our theoretical studies cover various fields of 'classical 'condensed matter theory, including the theory of disordered and amorphous systems, biological systems, or the study of dissipation and stopping in solids.