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Forschungsgruppe | Fundamental Noise Sources in Future Laser Interferometers

Der Gravitationswellendetektor GEO600 - In mehreren Gebäuden sind die Kontrolleinheiten des Experiments untergebracht. Die Anlage befindet sich in Ruthe bei Hannover. Foto: Albert-Einstein-Institut

Modern control is a relatively new approach to finding the optimal controller for a given problem.It is an inherently multi-variable approach, so nested loops can elegantly be taken into consideration during the design process of the controller. Many topical quantum optical experiments are multi-variable. The currently existing interferometric gravitational wave detectors – such as GEO 600 – consist of a multitude of subsystems, many of these interdependent, partially nested and intricately stabilised by means of literally hundreds of control loops. However, the stabilisation of these multi-input multi-output systems is still achieved solely by conventional means, i.e. measurement-based traditional control.

Measurement-based control requires the measurement of the observable of interest. Coherent control on the other hand is a fundamentally different approach: Where conventional control leaves the optical transfer function of the plant untouched, coherent control actually modifies the optical transfer function. It allows us to formulate a quantitative design objective and systematically engineer an optical system from first principles. Applied to the field of interferometric gravitational wave detection this could potentially result in entirely new interferometer topologies! The work in this newly founded junior research group is dedicated to finding a feasible approach to reaching the goal of merging coherent control and modern control for use in future laser interferometers and quantum optics.