Fast Tunable High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Q</mml:mi></mml:math>-Factor Superconducting Microwave Resonators
Sumedh Mahashabde, Ernst Otto, Domenico Montemurro, Sebastian de Graaf, Sergey Kubatkin, Andrey Danilov
Abstract
We present fast tunable superconducting microwave resonators fabricated from planar $\mathrm{Nb}\mathrm{N}$ on a sapphire substrate. The $3\ensuremath{\lambda}/4$ wavelength resonators are tuning fork shaped and tuned by passing a dc current that controls the kinetic inductance of the tuning fork prongs. The $\ensuremath{\lambda}/4$ section from the open end operates as an integrated impedance converter that creates a nearly perfect short for microwave currents at the dc terminal coupling points, thus preventing microwave energy leakage through the dc lines. We measure an internal quality factor ${Q}_{\mathrm{int}}>{10}^{5}$ over the entire tuning range. We demonstrate a tuning range of greater than $3\mathrm{%}$ and tuning response times as short as 20 ns for the maximum achievable detuning. Because of the quasifractal design, the resonators are resilient to magnetic fields of up to 0.5 T.