FABRICATION APPROACHES TO 3D SUPERCONDUCTING QUBIT RESONATORS WITH A HIGH Q-FACTOR*

RadiaBeam is presently developing a 3D quarter-wave resonator (QWR) with shape optimized for operation in the quantum regime. This program includes several important steps: development of a QWR cavity with the optimal shape to increase the Q-factor; increasing the Q-factor of the niobium resonator by adopting Nb surface treatment techniques from accelerating cavities; demonstration of the performance of a multi-qubit system with Josephson junctions, and improvement of fabrication techniques to reduce the complexity and costs of the system. The activities for most of the objectives are already ongoing. For example, we recently developed a resonator with the improved shape, machined it out of niobium, and tested it at a temperature of 10 mK. Other ongoing work includes the study of niobium surface treatments, and the use of advanced fabrication techniques such as additive manufacturing (AM), hydroforming or electro-hydraulic forming. In this talk, we will discuss the current and future fabrication activities of qubit cavities at RadiaBeam.