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

Abstract: Superconducting coplanar waveguide (SCPW) resonators with high internal quality factors (\Q_i) 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_{\parallel})). Temperature-dependent transmission measurements agree well with Mattis-Bardeen theory, revealing kinetic inductance parameters. Comparative analysis shows that 45-nm-thick NbTi resonators maintain (Q_i = 1.01 \times 10^{4}) at ((B_{\parallel})) = 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.