The physics of superconducting ring resonators

Superconducting microwave resonators with very high quality factor have been widely used in a large number of low-temperature experiments and applications over the past two decades. Numerous research on linear distributed, either half-wavelength or quarter-wavelength, and lumped element superconducting resonators, has led to a better understanding of their underlying physics and substantially improved resonator performance. However, there is another possible resonator geometry, one-wavelength resonator in a closed-ring configuration. This geometry, made of either normal metals or optical waveguides, is extensively used in the field of microwave and photonics, but, to my knowledge, no superconducting microwave line version has been reported in the literature. In this thesis, I describe the theoretical and experimental research to explore the imple- mentation and underlying physics of superconducting ring resonators. I begin by developing the basic principles into a full theory about the behaviour of a four-port ring resonator capaci- tively coupled to external transmission lines at four evenly spaced points. I will illustrate the behaviour with several analytical and numerical models that allow the simulation of resonator electrothermal response for comparison in subsequent experimental measurements. I then present a new technique, based on four-port ring resonators, to measure directly the quasiparticle-phonon power flow of superconducting thin-film coplanar and microstrip transmission lines. In the middle chapters, I introduce the design, fabrication, measurement and data analysis of several batches of superconducting ring resonators using different ge- ometries and materials. Finally, I will extend the established models of superconducting ring resonators to investigate the potential effects of finite quasiparticle diffusion on the behaviour of ring resonators. Through this thesis I have implemented superconducting ring resonators for the first time, explored different aspects of the underlying physics of ring resonators, and discussed numerous potential applications of them.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Sun, Zhenyuan

Advisor dc:contributor.advisor

• Withington, stafford

• Superconducting resonators
• Ring Resonator
• Superconducting transmission line
• Quasiparticle heating
• Two level systems

Licence

• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.84455

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/337033