Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: Transport - Poster Session

TT 28.23: Poster

Thursday, March 29, 2007, 14:00–17:45, Poster A

Superconducting coplanar waveguide resonators for flux qubit readout — •Markus Rösch, Stefan Wünsch, Alexander Stassen, Hansjürgen Wermund, and Michael Siegel — Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe, D-76187 Karlsruhe

The usage of an transmission line resonator offers a method for flux qubit readout. For a required weak electromagnetic coupling there is a need for a high quality factor Q_L of the cavity circuit to detect small deviations in the resonance frequency.

We developed various superconducting niobium coplanar waveguide resonators for a resonance frequency of 3 GHz and a linewidth of 50 µ m. Different layouts for the resonator were designed, simulated and measured on a silicon substrate at 4.2 K. We found a very good agreement between simulation and measurement results. The presented results showed a big influence of the substrate properties in respect of Q_L. To analyse the dependence of this value we implemented the resonator structure with the highest Q_L value on a sapphire substrate. In respect of the lower losses in the substrate we obtained an increasing of Q_L. Finally we discuss the results and give an outlook of future activities.