High-Q superconducting coplanar waveguide resonators for integration into molecule ion traps

Abstract

Over the last decade, quantum information experiments with trapped ions have demonstrated essential steps towards quantum computing and quantum simulation. Large fields are required to achieve strong coupling to the ions via dipolar interactions, and so we fabricated transmission line microresonators-capable of producing large fields in a standing wave at resonance-for eventual integration into 2D ion trap structures. The resonators were superconducting to minimize loss and maximize quality factor. We fabricated the resonators as two dimensional coplanar waveguides in niobium on R-plane sapphire using optical lithography. Resist was patterned on the niobium using optical lithography, developed, then reactive-ion etched to transfer the pattern into the niobium. The resonators were cooled and tested in a cryogenic probe station and characterized with a network analyzer. Additionally, the resonator geometry was reproduced in commercial microwave simulation software. Results from our fabricated resonators showed first-resonance quality factors of 1.2x 104 at 3.23 GHz at device temperatures of 3-4 K.