The Power of Photons: from many to just one

The laser is "a solution seeking a problem" - this statement by Theodore Maiman has long proven obsolete. In our group we pursue several projects where the laser is either the central element of our investigation or is an integral part of the "solution". In this talk, we will give a brief overview of the projects in our group. Specifically, we will discuss three projects in more detail: the first is a very active research collaboration with researchers from GSI gearing at developing laser sources for cooling of highly relativistic ion beams at FAIR/GSI. The second aims at demonstrating for the first time lasing without inversion at UV wavelengths. During the last part of my talk we will detail our efforts in quantum key distribution based on a heralded single photon source.