The effect of microwaves on superconductors for kinetic inductance detection and parametric amplification

TL;DR

This paper investigates how microwave radiation interacts with superconductors, affecting their use in kinetic inductance detectors and parametric amplifiers, by combining microscopic theory with experimental spectral measurements to improve device performance understanding.

Contribution

It introduces an experimental system to measure spectral functions and non-equilibrium distributions in microwave-driven superconductors, revealing limits of phenomenological models.

Findings

Identified microwave interaction as a source of dissipation in superconducting resonators.

Proposed measurement techniques for spectral functions and non-equilibrium states.

Provided insights for optimizing superconducting microwave device performance.

Abstract

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.