Non-linearity in the system of quasiparticles of a superconducting resonator

TL;DR

This paper investigates the strong non-linear behavior of quasiparticles in a superconducting aluminum resonator, revealing feedback effects that significantly influence quasiparticle relaxation times and attributing most of the non-linearity to quasiparticles.

Contribution

It demonstrates the dominant role of quasiparticles in non-linearity and feedback effects in superconducting resonators, with quantitative estimates of their impact.

Findings

Quasiparticle non-linearity can alter relaxation times by over tenfold.

Feedback effects depend on readout frequency detuning.

Approximately 70% of the device's non-linearity is due to quasiparticles.

Abstract

We observed a strong non-linearity in the system of quasiparticles of a superconducting aluminum resonator, due to the Cooper-pair breaking from the absorbed readout power. We observed both negative and positive feedback effects, controlled by the detuning of the readout frequency, which are able to alter the relaxation time of quasiparticles by a factor greater than 10. We estimate that the (70+/-5) % of the total non-linearity of the device is due to quasiparticles.