Tantalum microwave resonators with ultra-high intrinsic quality factors

We acquire tantalum thin film in its alpha phase (alpha-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 alpha-Ta film and characterized at millikelvin in a dilution refrigerator. In the single photon regime, an intrinsic quality factor (Q(i)) up to 3 x 10(6) is obtained in these resonators. At high power, Q(i) rises to 6 x 10(6). Moreover, we also fabricate an array with 7 x 7 lumped element resonators using the alpha-Ta film. The array shows excellent uniformity. At high power, Q(i)s of all pixels exceed 1 x 10(6). In the single photon regime, Q(i)s of over 90% pixels exceed 1 x 10(6). Superconducting quantum computing and ultrasensitive electromagnetic wave detectors will benefit a lot from devices based on the alpha-Ta film. Published under an exclusive license by AIP Publishing.