Quasiparticle Dynamics in NbN Superconducting Microwave Resonators at Single Photon Regime

TL;DR

This paper investigates how quasiparticle energy distributions affect the performance of NbN superconducting microwave resonators, providing insights into decoherence mechanisms in quantum circuits at the single photon level.

Contribution

It offers a detailed analysis of quasiparticle effects on NbN resonators by measuring resonance and quality factors and calculating complex conductivity, advancing understanding of decoherence sources.

Findings

Resonance frequency shifts with temperature indicate quasiparticle influence.

Internal quality factor decreases as quasiparticle density increases.

Complex conductivity calculations correlate quasiparticle density with resonator performance.

Abstract

Exchanging energy below the superconducting gap introduces quasiparticle energy distributions in superconducting quantum circuits, which will be responsible for their decoherence. This study examines the impact of quasiparticle energy on the performance of NbN superconducting microwave coplanar waveguide resonators on silicon chips. We measured the resonance frequency and internal quality factor in response to temperature sweeps to evaluate the effect of quasiparticle dynamics. Moreover, by calculating the complex conductivity of the NbN film, we identified the contribution of quasiparticle density to the experimental results.