Source approach to quantum systems in atomic and mesoscopic physics

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A macroscopic and complex physical system does not require an entirely quantum mechanical description. As such, typically a combined quantum and classical approach is needed. The interface between the classical and quantum parts of the system can be expressed in terms of sources, which emit quantum particles in the form of matter waves. Examples of sources are the contacts through which electrons are injected into a nanodevice, trapped clouds of cold atoms, or the breaking of chemical bonds. My research proposed is focused on the source description of systems for which other theoretical approaches suffer from severe limitations. For example, previous theories of transport rarely include long-range potentials because no perturbative expansion is available, and the localization of the source prohibits the use of translational invariance and periodic boundary conditions. However, it are mainly long-range potentials which affect the propagation in the quantum system and can be used to tune it for high-precision experiments. The new theoretical approaches put forward in my research proposal provide ways to calculate particle current distributions and combine methods from theoretical atomic physics with those of condensed matter theory. Areas of applications are the precise analysis of quantum states, interferometric methods for atoms and electrons, and mesoscopic transport through nanostructures.