Enhanced superconducting qubit performance through ammonium fluoride etch

Enhanced superconducting qubit performance through ammonium fluoride etch

The performance of superconducting qubits is often limited by dissipation and two-level systems (TLS) losses. The dominant sources of these losses are believed to originate from amorphous materials and defects at interfaces and surfaces, likely as a result of fabrication processes or ambient exposur...

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Main Authors: Cameron J Kopas, Dominic P Goronzy, Thang Pham, Carlos G Torres Castanedo, Matthew Cheng, Rory Cochrane, Patrick Nast, Ella Lachman, Nikolay Z Zhelev, André Vallières, Akshay A Murthy, Jin-su Oh, Lin Zhou, Matthew J Kramer, Hilal Cansizoglu, Michael J Bedzyk, Vinayak P Dravid, Alexander Romanenko, Anna Grassellino, Josh Y Mutus, Mark C Hersam, Kameshwar Yadavalli
Format: Article
Language:English
Published: IOP Publishing 2024-01-01
Series:Materials for Quantum Technology
Subjects:
superconducting qubits
two-level systems
fabrication
interfaces
Online Access:https://doi.org/10.1088/2633-4356/ad88cc
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Summary:The performance of superconducting qubits is often limited by dissipation and two-level systems (TLS) losses. The dominant sources of these losses are believed to originate from amorphous materials and defects at interfaces and surfaces, likely as a result of fabrication processes or ambient exposure. Here, we explore a novel wet chemical surface treatment at the Josephson junction-substrate and the substrate-air interfaces by replacing a buffered oxide etch (BOE) cleaning process with one that uses hydrofluoric acid followed by aqueous ammonium fluoride. We show that the ammonium fluoride etch process results in a statistically significant improvement in median $\text{T}_1$ by $\sim22\%$ ( p  = 0.002), and a reduction in the number of strongly-coupled TLS in the tunable frequency range. Microwave resonator measurements on samples treated with the ammonium fluoride etch after niobium deposition and etching also show $\sim33\%$ lower TLS-induced loss tangent compared to the BOE treated samples. As the chemical treatment primarily modifies the Josephson junction-substrate interface and substrate-air interface, we perform targeted chemical and structural characterizations to examine materials differences at these interfaces and identify multiple microscopic changes that could contribute to decreased TLS losses.
ISSN:2633-4356

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