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Characterizing and Mitigating Loss in Interfacial Dielectrics in Superconducting Quantum Circuits

Mitchell J. Walker

Jan 1, 20250 citations

Noise and loss from the dielectric environment of planar superconducting circuits

Jonathan Burnett, Andreas Bengtsson, Per Delsing +1 more

Bulletin of the American Physical SocietyMar 9, 20180 citations

Eliminating Surface Oxides of Superconducting Circuits with Noble Metal Encapsulation

Ray Chang, Nana Shumiya, Russell A. McLellan +16 more

The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems in the surface tantalum oxide. Here, we demonstrate a strategy for avoiding oxide formation by encapsulating the tantalum with noble metals that do not form native oxide. By depositing a few nanometers of Au or AuPd alloy before breaking vacuum, we completely suppress tantalum oxide formation. Microwave loss measurements of superconducting resonators reveal that the noble metal is proximitized, with a superconducting gap over 80% of the bare tantalum at thicknesses where the oxide is fully suppressed. Our findings suggest that losses in resonators fabricated by subtractive etching are dominated by oxides on the sidewalls, pointing to total surface encapsulation by additive fabrication as a promising strategy for eliminating surface oxide two-level system loss in superconducting qubits.The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems in the surface tantalum oxide. Here, we demonstrate a strategy for avoiding oxide formation by encapsulating the tantalum with noble metals that do not form native oxide. By depositing a few nanometers of Au or AuPd alloy before breaking vacuum, we completely suppress tantalum oxide formation. Microwave loss measurements of superconducting resonators reveal that the noble metal is proximitized, with a superconducting gap over 80% of the bare tantalum at thicknesses where the oxide is fully suppressed. Our findings suggest that losses in resonators fabricated by subtractive etching are dominated by oxides on the sidewalls, pointing to total surface encapsulation by additive fabrication as a promising strategy for eliminating surface oxide two-level system loss in superconducting qubits.

arXiv:2408.13051Physical Review LettersMar 6, 202532 citations

Materials for superconducting qubits: Measurements of dielectric loss at low temperatures

A. D. O’Connell, M. Ansmann, Radoslaw C. Bialczak +9 more

Bulletin of the American Physical SocietyMar 11, 20080 citations

Low-loss α-tantalum coplanar waveguide resonators on silicon wafers: fabrication, characterization and surface modification

Daniel Pérez Lozano, Massimo Mongillo, X Piao +19 more

Abstract The performance of state-of-the-art superconducting quantum devices is currently limited by microwave dielectric loss at different interfaces. α -tantalum is a superconductor that has proven effective in reducing dielectric loss and improving device performance due to its thin low-loss oxide. Here, we demonstrate the fabrication of high-quality factor α -tantalum coplanar-waveguide resonators directly on pristine 300 mm silicon wafers over a variety of metal deposition conditions and perform a comprehensive material and electrical characterization study. Additionally, we apply a surface treatment based on hydrofluoric acid that allows us to modify different resonators surfaces, leading to a reduction in two-level system loss in the devices by a factor of three. This loss reduction can be entirely attributed to the removal of surface oxides. Our study indicates that large scale manufacturing of low-loss superconducting circuits should indeed be feasible and suggests a viable avenue to materials-driven advancements in superconducting circuit performance.Abstract The performance of state-of-the-art superconducting quantum devices is currently limited by microwave dielectric loss at different interfaces. α -tantalum is a superconductor that has proven effective in reducing dielectric loss and improving device performance due to its thin low-loss oxide. Here, we demonstrate the fabrication of high-quality factor α -tantalum coplanar-waveguide resonators directly on pristine 300 mm silicon wafers over a variety of metal deposition conditions and perform a comprehensive material and electrical characterization study. Additionally, we apply a surface treatment based on hydrofluoric acid that allows us to modify different resonators surfaces, leading to a reduction in two-level system loss in the devices by a factor of three. This loss reduction can be entirely attributed to the removal of surface oxides. Our study indicates that large scale manufacturing of low-loss superconducting circuits should indeed be feasible and suggests a viable avenue to materials-driven advancements in superconducting circuit performance.

arXiv:2211.16437Materials for Quantum TechnologyMay 14, 202424 citations

Addressing surface-induced loss and decoherence in superconducting quantum circuits

Andreas Fuhrer, Peter R. Müeller, Andreas V. Kuhlmann +3 more

Bulletin of the American Physical SocietyMar 15, 20170 citations

A study of intrinsic dielectric loss of tantalum based superconducting quantum circuits

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