Fabrication and Characterization of Magnetic-Field-Resilient MoRe Superconducting Coplanar Waveguide Resonators

Abstract: Magnetic-field-resilient superconducting coplanar waveguide (SCPW) resonators are essential for developing integrated quantum circuits of various qubits and quantum memory devices. Molybdenum-Rhenium (MoRe), which is a disordered superconducting alloy forming a highly transparent contact to the graphene and carbon nanotubes (CNTs), would be a promising platform for realizing the field-resilient SCPW resonators combined with graphene- and CNT-based nano-hybrid qubits. We fabricated MoRe SCPW resonators and investigated their microwave transmission characteristics with varying temperature and external magnetic field. Our observations show that the thickness of MoRe film is a critical parameter determining the lower critical field, kinetic inductance, and characteristic impedance of the SCPW resonator, resulting in drastic changes in the quality factor and the resonance frequency. As a result, we obtained a maximum value of $Q_{i} > 10^{4}$ in parallel magnetic fields up to $B_{||} = 0.15$ T for the 27-nm-thick MoRe resonator. Our experimental results suggest that MoRe SCPW resonator would be useful for integrating nano-hybrid spin or gatemon qubits and for developing spin-ensemble quantum memory devices.