On-chip high kinetic inductance LC filters modeled with a distributed circuit model

In a hybrid system of quantum dots coupled with microwave resonators, to address the large footprints challenge posed by conventional-material on-chip low-pass filters which are inserted to suppress resonator photon leakage, the utilization of filters with high kinetic inductance (HKI) materials has been demonstrated. However, the HKI film induces the distributed parasitic kinetic inductance to the capacitor structure, making the lumped circuit model which generally used to simulate the filter face failure, and hindering the superconducting filter performance. In our work, we fabricate a compact HKI planar filter and observe that the measured response curve exhibits a large deviation from the simulation result of the lumped circuit model. We propose a distributed circuit model to more accurately simulate transmission characteristics of the HKI filter. By analyzing the effect of parasitic inductance induced by the distributed kinetic inductance film, we explain the abnormal roll-off phenomenon observed in the transmission response curve of the HKI filter. Combining the Fano effect, the simulation result with the distributed model exhibits better correspondence with the experimental results than that of the lumped model. The developed circuit model will contribute to analyzing the adverse effects and optimizing the device design of the HKI film. Graphical abstract