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Title: Loss mechanisms in superconducting thin film microwave resonators

We present a systematic analysis of the internal losses of superconducting coplanar waveguide microwave resonators based on niobium thin films on silicon substrates. In particular, we investigate losses introduced by Nb/Al interfaces in the center conductor, which is important for experiments where Al based Josephson junctions are integrated into Nb based circuits. We find that these interfaces can be a strong source for two-level state (TLS) losses, when the interfaces are not positioned at current nodes of the resonator. In addition to TLS losses, for resonators including Al, quasiparticle losses become relevant above 200 mK. Finally, we investigate how losses generated by eddy currents in conductive material on the backside of the substrate can be minimized by using thick enough substrates or metals with high conductivity on the substrate backside.
Authors:
; ; ; ; ; ; ;  [1] ;  [2] ; ; ; ;  [1] ;  [2] ;  [3] ;  [1]
  1. Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany)
  2. (Germany)
  3. (NIM), Schellingstraße 4, 80799 München (Germany)
Publication Date:
OSTI Identifier:
22494871
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; EDDY CURRENTS; INTERFACES; JOSEPHSON JUNCTIONS; LOSSES; MICROWAVE RADIATION; NIOBIUM; RESONATORS; SILICON; SUBSTRATES; THIN FILMS; WAVEGUIDES