Tantalum microwave resonators with ultra-high intrinsic quality factors.

We acquire tantalum thin film in its α phase (α-Ta) using direct-current magnetron sputtering. According to x-ray diffraction results, 110-Ta is dominant. Quarter-wavelength coplanar waveguide resonators are fabricated with the α-Ta film and characterized at millikelvin in a dilution refrigerator. In the single photon regime, an intrinsic quality factor (Qi) up to 3 × 10 6 is obtained in these resonators. At high power, Qi rises to 6 × 10 6 . Moreover, we also fabricate an array with 7 × 7 lumped element resonators using the α-Ta film. The array shows excellent uniformity. At high power, Qis of all pixels exceed 1 × 10 6 . In the single photon regime, Qis of over 90% pixels exceed 1 × 10 6 . Superconducting quantum computing and ultrasensitive electromagnetic wave detectors will benefit a lot from devices based on the α-Ta film. [ABSTRACT FROM AUTHOR]