{"id":636921,"date":"2026-10-05T10:20:12","date_gmt":"2026-10-05T10:20:12","guid":{"rendered":"https:\/\/www.newsbeep.com\/il\/636921\/"},"modified":"2026-10-05T10:20:12","modified_gmt":"2026-10-05T10:20:12","slug":"sqms-study-links-qubit-performance-to-material-and-fabrication-features","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/il\/636921\/","title":{"rendered":"SQMS Study Links Qubit Performance to Material and Fabrication Features"},"content":{"rendered":"

Insider Brief<\/p>\n

Researchers from the Fermilab-led<\/a> SQMS Center identified material and fabrication features associated with variations in superconducting qubit performance.<\/p>\n

The study examined 22 superconducting transmon qubits using seven materials-characterization techniques alongside quantum coherence measurements.<\/p>\n

Researchers identified oxide thickness, etched sidewall angles and trench depth as key features linked to performance differences, with the three factors accounting for up to a twofold variation among the studied qubits.<\/p>\n

This story is based directly on reporting published by Fermilab<\/a> on the SQMS study.<\/p>\n

PRESS RELEASE \u2014 Understanding why some superconducting qubits outperform others remains one of the most important challenges in quantum computing. As long as the quantum state in a qubit maintains its coherence and does not decay, information can be held and potentially processed in advanced calculations far beyond the capabilities of current computers.<\/p>\n

\u201cAdvancing quantum information science is fundamentally tied to our ability to control matter at the atomic level.\u201d<\/p>\n

Bindu Nair, U.S. Department of Energy<\/p>\n

\"Introducing<\/a>\"Introducing<\/a><\/p>\n

While over the past decade researchers have identified many possible coherence-limiting defects in the materials used to make the qubits, establishing which microscopic features explain why identically designed qubits may perform differently has remained a challenge. Now, researchers from the Fermi National Accelerator Laboratory-led Superconducting Quantum Materials and Systems Center, or SQMS, have completed one of the most comprehensive studies ever conducted, linking materials and their structures \u2014 including surfaces, interfaces and geometries \u2014 to variations in quantum device performance. This research provides new insights that directly connect to device fabrication, an important step on the path toward building practical and reliable quantum computers.<\/p>\n

In a large-scale study involving Fermilab<\/a>, Northwestern University, Rigetti Computing, Ames National Laboratory, National Institute of Standards and Technology, and National Physical Laboratory, SQMS researchers examined 22 superconducting transmon qubits fabricated by Fermilab, Rigetti and NIST. A transmon is a specific type of superconducting qubit, engineered to be far less sensitive to the small fluctuations in electric charge that can flip a qubit\u2019s state, making it one of the most widely used qubit designs in superconducting quantum computing today. Using seven different materials-characterization techniques, the teams documented the material properties of quantum devices exhibiting varying levels of quantum-state coherence and investigated correlations with device-performance data. The study\u2019s findings have been published in Applied Physics Reviews.<\/a><\/p>\n

\u201cAdvancing quantum information science is fundamentally tied to our ability to control matter at the atomic level,\u201d said Bindu Nair, associate director of Basic Energy Science at the U.S. Department of Energy. \u201cThe coordinated effort led by SQMS provides a scientifically grounded guide to the material defects behind variability in superconducting device performance, moving us from observation to correlation. This foundational knowledge is essential to building the next generation of reliable, reproducible and powerful quantum technologies for the nation.\u201d<\/p>\n

A Study Based on Correlations<\/p>\n

For years, SQMS researchers have investigated how materials, interfaces and surface chemistry affect the coherence of quantum states in superconducting qubits. Pre-dating the center\u2019s work, Fermilab<\/a> researchers studied cavities that preserve high-coherence<\/a> states, and used them to understand how niobium oxides influence the performance of quantum devices. Throughout the lifetime of the center, understanding and controlling the oxides<\/a> with thermal processing has remained a focus. These studies contributed to the development of surface encapsulation<\/a> approaches designed to protect superconducting surfaces and improve performance.<\/p>\n

\u201cThe strength of this study is that it brought together many techniques, many devices and many partners.\u201d<\/p>\n

Akshay Murthy, Fermilab<\/a><\/p>\n

Despite these extensive advances, challenges remain in achieving uniformly high qubit performance. Superconducting qubits can be fabricated on the same chip, using the same nominal processes and materials, and still perform differently. For quantum researchers, that variation points to one of the field\u2019s central materials science questions: What, at the microscopic level, causes one qubit to maintain quantum information longer than another?<\/p>\n

\u201cThis study was based on systematically comparing high-performing versus low-performing devices side-by-side,\u201d said Alexander Romanenko, SQMS technology leader. \u201cBecause those devices share the same design and are fabricated together from the same materials, any difference in how they performed had to come down to something more subtle. Over the past two decades, we have successfully developed this methodology to understand and improve the performance of superconducting radio frequency cavities, and with SQMS we decided to apply it for the first time to superconducting qubits.\u201d<\/p>\n

\"AkshayAkshay Murthy, SQMS Center deputy director and materials science group leader, applies state-of-the-art characterization techniques in the Materials Science Lab, such as time-of-flight secondary ion mass spectroscopy, and X-ray photoelectron spectroscopy, to understand materials-level sources leading to performance variations in superconducting qubits. Credit: JJ Starr, Fermilab<\/a><\/p>\n

To achieve this goal, the team paired a variety of microscopy and spectroscopy techniques across Fermilab<\/a>, Ames National Laboratory, and Northwestern University with quantum coherence characterization for qubit states performed in the SQMS Quantum Garage at Fermilab.<\/p>\n

\u201cNo single measurement tells the whole story,\u201d said Akshay Murthy, deputy director of the SQMS Center. \u201cThe strength of this study is that it brought together many techniques, many devices and many partners. By combining those data sets, we were able to identify generalizable trends that would be very difficult to see from one device or one characterization method alone.\u201d<\/p>\n

By determining which defects correlate with performance variation from one qubit to the next, researchers can target those defects through improved materials processing, fabrication techniques and surface treatments. For SQMS, that makes the study more than a retrospective analysis of device performance. It provides a roadmap for future work.<\/p>\n

A Bias-Free look at Qubit Materials<\/p>\n

The study was designed to remove bias from the process, and researchers who characterized the devices did not know how the qubits had performed. Instead, each team examined the devices, documented the features they observed and quantified those features as thoroughly as possible. Only after the data was collected did researchers look for correlations between materials defects and variations in qubit performance.<\/p>\n

\"ElectronElectron microscopy images show three material features that were observed to be linked to variations in the performance of superconducting qubits. These include the thickness of oxides that form on the surface of these qubits, the subtle variations in angle present at sidewalls of qubits, and the trench depth \u2014 a measure of how deep a trench is carved into the substrate immediately neighboring the device. Graphic: SQMS Center, Fermilab<\/a><\/p>\n

\u201cThe challenge we gave ourselves was a blind study where we didn\u2019t reveal the energy relaxation lifetimes (T1) \u2014 how quickly an excited quantum state loses energy \u2014 of the devices before we started a comprehensive study of the qubits,\u201d said Matt Kramer, distinguished scientist at Ames National Laboratory. \u201cThe first tests we did were non-destructive, with many of those methods allowing us to recognize features which we could then look at with higher resolution and employ more invasive methods. This approach allowed an unbiased decision tree to look for features that could be linked to variations in qubit performance.\u201d<\/p>\n

The analysis pointed to three features that stood out in relation to variations in device performance: the depth of the trenches around device structures, the angle of the etched sidewalls and the thickness of the oxide layer on the surface.<\/p>\n

Surface oxide-layer thickness reflects the chemistry of the superconducting surface. Prior SQMS work<\/a> showed this layer, though only a few nanometers thick, dominates losses in niobium qubits. This study adds that even single nanometer variations in oxide thickness from device-to-device can meaningfully shift performance.<\/p>\n

Sidewall angles are tied to how device structures are patterned and etched during fabrication. Electromagnetic simulations indicate that a sharp angle of approximately 10-15 degrees reduces the electric field stored in lossy oxides and predicts improvement in performance by 20 to 30% compared to a broader, more tapered angle of around 30 degrees.<\/p>\n

Trench depth was also found to significantly contribute to variations in qubit performance. This represents the vertical distance of the recesses etched into the underlying substrate \u2014 the foundation of the qubit \u2014 immediately adjacent to the edges of the superconducting metal electrodes. At trench depths below approximately 20 nanometers, small variations have a more dramatic effect on device performance. At a larger trench depth, this effect saturates and other factors play a more prominent role. Like sidewall angles, trench depths are also tied to fabrication.<\/p>\n

In contrast, the team also examined macroscopic defects, such as surface scratches, particulates and similar visible imperfections, but found no clear correlation between these features and device performance, suggesting that for this set of devices, nanoscale differences in surface chemistry and etch geometry matter more to performance variation than damage visible to the eye.<\/p>\n

Collectively, the findings indicate that both fabrication geometry and surface chemistry help explain the reproducibility of device performance. Across the devices studied, differences in these three features accounted for as much as a twofold variation in performance among qubits fabricated from identical materials. This evidence therefore points to tighter control over trench depth, sidewall angle and oxide thickness as a way to narrow that spread.<\/p>\n

Guidance for Quantum Manufacturing<\/p>\n

For industry partners, the findings offer something that has been difficult to obtain: scientifically grounded guidance on which materials and fabrication features deserve the most attention.<\/p>\n

Companies such as Rigetti Computing can fabricate devices repeatedly and at scale, but they often lack the breadth of knowledge and tools to investigate every possible cause of performance variation in depth. That makes the SQMS collaboration especially valuable.<\/p>\n

\u201cAs we scale to larger quantum processors, performance isn\u2019t set by our best qubits \u2014 it\u2019s set by our worst ones, since a single low-performance qubit can drag down the fidelity of any computation that relies on it,\u201d Andrew Bestwick, chief technology officer at Rigetti, said. \u201cNarrowing that spread across a chip matters just as much as pushing our best qubits further, and that\u2019s exactly the kind of problem this study starts to give us a scientific handle on.\u201d<\/p>\n

\u201cThe SQMS study gives companies a stronger basis for determining which changes are worth pursuing.\u201d<\/p>\n

Andrew Bestwick, Rigetti Computing<\/p>\n

For Rigetti, the study addresses questions that are directly connected to device fabrication. \u201cWe have wondered ourselves: What sidewall angle should we engineer our etch to have? How deep should the trench go? How much should we prioritize these lithographic features?\u201d Bestwick said. \u201cVery few people have been able to establish answers to these questions scientifically.\u201d<\/p>\n

That information could help guide future manufacturing decisions.<\/p>\n

\u201cIn industry, process changes must be made carefully and in a controlled way to keep fabrication stable and reproducible,\u201d Bestwick said. \u201cThe SQMS study gives companies a stronger basis for determining which changes are worth pursuing.\u201d<\/p>\n

A Roadmap Towards Reproducible Qubits<\/p>\n

The work represents an important milestone in SQMS\u2019s broader mission to establish the scientific foundations of scalable quantum computing. While the study identifies several materials and fabrication features strongly associated with qubit performance, researchers view these results as the beginning rather than the end of the journey. In this initial study, the team established which material features help explain energy relaxation. The team\u2019s next step is to extend the analysis to dephasing and T2 coherence, which refers to how long a qubit can maintain phase information, a critical parameter for gate fidelity in multi-qubit processors.<\/p>\n

Future studies will expand the range of materials systems, device architectures and characterization approaches, building increasingly predictive models that connect materials processing directly to quantum performance.<\/p>\n

\u201cWhat makes this work unique is not only the scale of the study, but the breadth of expertise brought together through SQMS,\u201d said Anna Grassellino, Fermilab<\/a> chief technology officer and SQMS center director. \u201cBy uniting leading institutions, advanced characterization capabilities and quantum hardware platforms, we are beginning to transform quantum device development from an art into a predictive science. That foundation will be critical as we move toward larger, more powerful quantum systems.<\/p>\n

As superconducting quantum processors continue to include more qubits and more complex connections, the ability to engineer coherence through a deep understanding of materials is increasingly essential. The SQMS collaboration is helping build that foundation, and with it, a new standard for how quantum hardware is developed and understood.<\/p>\n

And the work continues.<\/p>\n","protected":false},"excerpt":{"rendered":"Insider Brief Researchers from the Fermilab-led SQMS Center identified material and fabrication features associated with variations in superconducting…\n","protected":false},"author":2,"featured_media":636922,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[85,46,370,141],"class_list":["post-636921","post","type-post","status-publish","format-standard","has-post-thumbnail","category-physics","tag-il","tag-israel","tag-physics","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/636921","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=636921"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/636921\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/636922"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=636921"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=636921"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=636921"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}