Date of Award
May 2016
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics
Advisor(s)
B. L. T. Plourde
Keywords
magnetic flux vortices, microwave resonant circuits, (NIS)-tunnel junctions, Quasiparticles, Superconducting resonators, Superconductivity
Subject Categories
Physical Sciences and Mathematics
Abstract
Superconducting resonators with high quality factors are of great interest in many areas. However, the quality factor of the resonator can be weakened by many dissipation channels including trapped magnetic flux vortices and nonequilibrium quasiparticles which can significantly impact the performance of superconducting microwave resonant circuits and qubits at millikelvin temperatures. Quasiparticles result in excess loss, reducing resonator quality factors and qubit lifetimes. Vortices trapped near regions of large microwave currents also contribute excess loss. However, vortices located in current-free areas in the resonator or in the ground plane of a device can actually trap quasiparticles and lead to a reduction in the quasiparticle loss. In this thesis, we will describe experiments involving the controlled trapping of vortices for reducing quasiparticle density in the superconducting resonators. We provide a model for the simulation of reduction of nonequilibrium quasiparticles by vortices. In our experiments, quasiparticles are generated either by stray pair-breaking radiation or by direct injection using normal-insulator-superconductor (NIS)-tunnel junctions.
Access
Open Access
Recommended Citation
Nsanzineza, Ibrahim, "Vortices and Quasiparticles in Superconducting Microwave Resonators" (2016). Dissertations - ALL. 446.
https://surface.syr.edu/etd/446
