Field-resilient superconducting coplanar waveguide resonators made of Nb, NbTi, and NbTiN

Abstract

Superconducting coplanar waveguide (SCPW) resonators with high internal quality factors (Qi) are essential for quantum information applications, but suffer severe Qi degradation under magnetic fields due to quasiparticle generation and vortex-induced losses. We fabricated and characterized Nb, NbTi, and NbTiN SCPW resonators with varying film thicknesses under different temperatures and in-plane magnetic fields (B||). Temperature-dependent transmission measurements agree well with Mattis-Bardeen theory, revealing kinetic inductance parameters. Comparative analysis shows that 45-nm-thick NbTi resonators maintain Qi = 1.01 x 104 at B|| = 0.4 T, satisfying the dual requirements of high Qi and strong field resilience. Owing to its moderate kinetic inductance and compatibility with conventional photolithography, NbTi emerges as a practical material platform for field-resilient SCPW resonators and hybrid quantum circuits operating in magnetic environments.