Introduction: superposition-based metrology
Quantum mechanics allows generating superposition states, where a physical system can have two different properties like energy, momentum, or position in space, at the same time. These states, beyond being conceptually intriguing and non-intuitive, have important technological application; they allow to realize a new type of quantum bit for information science, they are at the heart of high-precision atomic clocks. Spatially delocalized states are used in interferometry for measuring gravity and for sensing rotations and accelerations.
Such superposition states are notoriously fragile and difficult to prepare as they are encountered primarily at the microscopic scale of single atoms and molecules. On the other hand, quantum mechanical properties, e.g. transition energies, are perfectly universal and reproducible quantities (based in the indistinguishability of particles) and hence ideally suited to implement standards for physical quantities. It is the aim of the research group to investigate novel quantum systems with regards to metrology applications (“quantum metrology”)
Especially laser spectroscopy and atomic clocks have reached an incredible level of accuracy and allow to put constrains on fundamental constants of physics like the fine structure/Rydberg constant. It is generally accepted, that further progress will be made going to higher transition energies such as optical atomic clocks. We are investigating new approaches to optical frequency standards, such as “active” and “nuclear” optical clocks.
Spatial superpositions and non-local entanglement are probably the most bizarre manifestations of quantum physics, violating local realism as we encounter it in day-to-day life. As these states explore extended regions in space, they are extremely sensitive to local forces and fields, and can be used as sensitive probes and inertial sensors. Our group in particular is performing interferometry with atomic matter waves.