LAUSR

We address, using concepts of the microscopic theory of superconductivity, parametric amplifiers and kinetic inductance detectors focusing on the interaction of microwave radiation with the superconducting condensate. This interaction was identified recently as the source of the apparent dissipation in microwave superconducting micro-resonators at low temperatures. Since the evaluation of the performance of practical devices based only on the microwave-response is not sufficiently informative about the underlying physical processes, we propose an experimental system to measure the microscopically relevant spectral functions as well as the non-equilibrium distribution function of a microwave-driven superconducting wire. The results indicate the limits of the commonly used phenomenological theories, providing the groundwork for further optimisation of the performance.