Sensors are vitally important tools for various technologies, such as, e.g., navigation, geo-prospecting, or the characterization of biological or
chemical materials. The exploitation of quantum phenomena offers the chance to develop novel powerful sensors to be applied in ultra-highprecision spectroscopy, positioning systems, clocks, gravitational, electrical and magnetic field measurements, and optical resolution beyond the wavelength limit. Quantum-based sensing technologies are increasingly important in fundamental research from the sub-nano to the galactic scale, as well as for the determination of the fundamental constants. But also in applied science, quantum-based sensing has become a powerful research tool, notably in biomedical science and diagnostics.