Characterization of internal quality factors in surface-treated and deep-etched superconducting CPW resonators

Abstract

For quantum computing with superconducting qubits, fabricating transmon qubits with increased coherence time is crucial, especially in view of multi-qubit quantum processors. The fabrication process, geometries and materials used to fabricate a transmon qubit are similar to the fabrication of CPW resonators. However, due to shorter fabrication time and straightforward measurement scheme of the latter, finding a way to increase the internal quality factor Q_i in a CPW resonator is a quick way to gain insight into methods to increase the coherence time of a transmon qubit. The main goal of this research is to characterize the Q_i at cryogenic temperature and single photon level of CPW resonators that are fabricated with novel surface treatments and etching techniques. The highest Q_i is observed for resonators etched using Deep Reactive Ion Etching and HDMS surface treatment, which reached ∼10⁶ at single photon level. This is comparable to the highest Q_i reported in literature so far.