Tunable resonators for quantum circuits

JLTP 3, 151 (2008)We have designed, fabricated and measured high-Q $\lambda/2$ coplanar waveguide microwave resonators whose resonance frequency is made tunable with magnetic field by inserting a DC-SQUID array (including $1$ or $7$ SQUIDs) inside. Their tunability range is $30\%$ of the zero field frequency. Their quality factor reaches up to 3$\times10^4$. We present a model based on thermal fluctuations that accounts for the dependance of the quality factor with magnetic field