Microwave Losses in YBCO Coplanar Waveguide Resonators at Low Power and Millikelvin Range

摘要

We have investigated the temperature dependence of microwave losses in the low-power limit and millikelvin temperature range of a thin-film (YBCO) coplanar waveguide resonator patterned on a (LSAT) substrate covered by a seed layer. The unloaded quality factor is mainly governed by the surface resistance of the YBCO film and the dielectric losses caused by resonant absorption due to a bath of two-level fluctuators in the dielectrics. The value of the unloaded quality factor at 20 mK and low power, i.e., , allows for the realization of YBCO microwave quantum circuits implementing biepitaxial grain-boundary Josephson junctions.