Losses in magnetic field resilient coplanar stripline resonators

Journal article, 2025

Coplanar waveguide (CPW) resonators have shown considerable success in circuit quantum electrodynamics research. However, their susceptibility to an external magnetic field limits their general functionality. In addition, electrical voltage gating for devices coupled to a CPW resonator necessitates alterations to the ground plane, changing the resonator characteristics. To avoid these problems, we fabricated and measured quarter wavelength differentially driven coplanar stripline (CPS) resonators made of NbTiN. We measured multiple devices with varying geometrical parameters in these novel resonators and analyse changes in their internal quality factor and two-level system losses. Furthermore, we establish the resilience of the resonators to an applied magnetic field by tracking the resonance frequency shift, without optimisation of the resonator geometry. Due to their flexible design and high magnetic field resilience, CPS resonators are particularly well-suited to study superconductor-semiconductor heterophysics where voltage gating or a magnetic field are necessary.