High Frequency Gravitational Wave Detection with Superconducting Microwave Cavities

So far, high frequency gravitational waves (GWs) remain unexplored messengers of new physics. Proposed sources in the MHz - GHz band include primordial black hole mergers, black hole superradiance and several stochastic backgrounds. Our collaboration is working on tapping into this source by employing superconducting microwave cavities for high precision measurements of harmonic displacements. The detection principle is to load an electromagnetic mode of a cavity so that a GW-induced vibration of the cavity walls up-converts some power into another, unloaded EM mode. The power in the unloaded mode is then taken to be the GW signal. This summary outlines the ongoing work and future plans of our project in Hamburg. Specifically, the potential sources, the cavity design, and the signal readout mechanism are discussed.