New Qubit Geometries with Minimal Participation of Dielectric in Resonant Modes

Loren Alegria | 22-FS-040

Project Overview

Current superconducting qubits suffer from quantum decoherence related to defects on the superconductor surfaces, interfaces, and within the substrate dielectric: everywhere, that is, except in the vacuum. If the vacuum-metal interface can be perfected, qubit devices can be made that are free from decoherence originating in their physical structure. Within a context of global efforts to root out sources of decoherence in superconducting qubits, we undertook to design and fabricate a qubit platform that would be insensitive to the substrate and any deleterious species at the substrate-metal interface, and would further provide a practical testbed for studies aimed at improving metal surfaces. We successfully demonstrated the production of this new qubit design and further, explored a new material system that improve the metal-vacuum interface over the current state-of-the-art.

Mission Impact

This feasibility broadly aided the development of Lawrence Livermore National Laboratory's superconducting device fabrication capabilities. During the course of the feasibility study, we measured the first qubit fabricated in-house. In addition to the direct accomplishments of the study, the resources provided by the study provided synergistic improvement of other fabrication technologies. Competency in new superconducting materials and devices directly supports the Lab's focus area of Quantum Science and Technology and its mission of maintaining U.S. leadership in sensing and computing technologies.

Publications, Presentations, and Patents

Alegria, Loren. "TLS loss in room-temperature-nucleated alpha-Ta resonators." Bulletin of the American Physical Society (2023). (