Frequency-tunable Superconducting Resonators via Nonlinear Kinetic Inductance
Michael R. Vissers, Johannes Hubmayr, Jiansong Gao, Martin Sandberg, Saptarshi Chaudhuri, Clint Bockstiegel
We have designed, fabricated and tested a frequency-tunable high-Q superconducting resonator made from niobium titanium nitride film. The frequency tunability is achieved by injecting a DC current through a special current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5~GHz while maintaining high internal quality factor $Q_i> 180,000$. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of superconductor at transition temperature and for readout of transition-edge sensors.