Princeton engineers have engineered a superconducting qubit that boasts a three-fold increase in stability compared to the most robust designs currently available, a significant leap forward in the quest for reliable quantum computers. This breakthrough addresses the fundamental challenge of qubit decoherence, where quantum information degrades rapidly, hindering the development of practical quantum computing. Andrew Houck, a leader in national quantum research and Princeton’s dean of engineering, emphasized the critical nature of this advancement, stating, "The real challenge, the thing that stops us from having useful quantum computers today, is that you build a qubit and the information just doesn’t last very long. This is the next big jump forward."

Published in the prestigious journal Nature on November 5th, the Princeton team’s research details a qubit capable of maintaining its quantum state, or coherence, for over 1 millisecond. This performance metric is triple the longest coherence time previously documented in laboratory settings and an astonishing fifteen times greater than the standard observed in industrial quantum processors. To validate their findings, the researchers constructed a functional quantum chip incorporating their novel qubit, demonstrating its capacity for error correction and its potential for scalability into larger quantum systems.

Crucially, the Princeton team’s qubit design is architecturally compatible with the systems developed by major players in the quantum computing arena, including Google and IBM. Their analysis projects that integrating Princeton’s innovative components into Google’s Willow processor could yield a thousandfold performance enhancement. Houck further elaborated that the advantages of this design compound exponentially as the number of qubits in a quantum system increases, suggesting a dramatic acceleration in quantum computing capabilities.

The Critical Importance of Enhanced Qubit Durability for Quantum Computing

Quantum computers hold immense promise for tackling complex problems that lie beyond the reach of even the most powerful conventional computers. However, their current utility is severely limited by the ephemeral nature of qubits, which lose their quantum information before intricate calculations can be completed. Consequently, extending qubit coherence times is paramount for the realization of practical quantum hardware. The advancement achieved by Princeton represents the most substantial gain in coherence time observed in over a decade.

While numerous research groups are exploring diverse qubit technologies, Princeton’s innovation builds upon the widely adopted transmon qubit architecture. Transmons, which operate as superconducting circuits maintained at cryogenic temperatures, are recognized for their resilience against environmental noise and their compatibility with established manufacturing processes.

Despite these inherent advantages, significantly increasing the coherence time of transmon qubits has presented a formidable obstacle. Recent findings from Google have highlighted material defects as the primary impediment to improving their most advanced processors.

A Novel Materials Strategy: Tantalum and Silicon Unite

The Princeton team’s ingenious solution to these material challenges involved a two-pronged approach. Firstly, they integrated tantalum, a metal renowned for its ability to retain energy in sensitive circuits. Secondly, they replaced the conventional sapphire substrate with high-purity silicon, a material that forms the bedrock of the modern computing industry. The direct deposition of tantalum onto silicon necessitated overcoming several technical hurdles related to their material interactions, but the researchers succeeded, uncovering substantial benefits in the process.

Nathalie de Leon, co-director of Princeton’s Quantum Initiative and a co-principal investigator on the project, highlighted that the tantalum-silicon design not only outperforms existing approaches but is also more amenable to large-scale manufacturing. "Our results are really pushing the state of the art," she stated.

Michel Devoret, chief scientist for hardware at Google Quantum AI and a recipient of the 2025 Nobel Prize in Physics, acknowledged the profound difficulty of extending the operational lifespan of quantum circuits, describing the pursuit as a "graveyard" of abandoned attempts. He commended de Leon’s tenacity, noting, "Nathalie really had the guts to pursue this strategy and make it work."

The project received principal funding from the U.S. Department of Energy’s National Quantum Information Science Research Centers and the Co-design Center for Quantum Advantage (C2QA). Houck, who directed C2QA from 2021 to 2025 and now serves as its chief scientist, was a key figure. Postdoctoral researcher Faranak Bahrami and graduate student Matthew P. Bland are credited as co-lead authors on the groundbreaking paper.

The Mechanism of Tantalum’s Enhancement of Qubit Stability

Houck, the Anthony H.P. Lee ’79 P11 P14 Professor of Electrical and Computer Engineering, elucidated the two primary determinants of a quantum computer’s efficacy: the sheer number of interconnected qubits and the number of operations each qubit can perform before accumulating errors. Improvements in individual qubit durability directly bolster both these factors. Extended coherence times inherently facilitate scalability and enhance the reliability of error correction mechanisms.

Energy loss stands as the most prevalent cause of system failure in quantum computing. Microscopic surface defects within metallic components can trap energy, disrupting qubit operations during computations. These disruptions magnify as more qubits are integrated into a system. Tantalum proves particularly advantageous due to its significantly lower propensity for these detrimental defects compared to metals like aluminum. A reduction in defects translates to fewer errors and a simplified process for rectifying those that do occur.

In 2021, Houck and de Leon introduced tantalum for superconducting chips, a development bolstered by the expertise of Princeton chemist Robert Cava, the Russell Wellman Moore Professor of Chemistry. Cava, a specialist in superconducting materials, became intrigued by the challenge after attending one of de Leon’s presentations. Their subsequent discussions led him to propose tantalum as a highly promising candidate. "Then she went and did it," Cava remarked. "That’s the amazing part."

Researchers across all three collaborating labs embraced this insight, fabricating a tantalum-based superconducting circuit on a sapphire substrate. The resulting circuit exhibited a marked improvement in coherence time, nearing the previous global benchmark.

Bahrami underscored tantalum’s exceptional durability, noting its ability to withstand the rigorous cleaning processes essential for removing contaminants during fabrication. "You can put tantalum in acid, and still the properties don’t change," she affirmed.

Following the elimination of contaminants, the team meticulously assessed the remaining sources of energy loss. They identified the sapphire substrate as the primary culprit. The transition to high-purity silicon effectively neutralized this loss mechanism. The synergy between tantalum and silicon, coupled with refined fabrication techniques, culminated in one of the most significant advancements ever achieved for transmon qubits. Houck characterized the outcome as "a major breakthrough on the path to enabling useful quantum computing."

Houck further projected that the exponential scaling benefits of this design mean that replacing current industry-leading qubits with Princeton’s innovation could render a theoretical 1,000-qubit computer approximately one billion times more effective.

A Silicon-Based Design Fosters Industry-Scale Growth

This groundbreaking project synergistically draws upon expertise from three distinct fields. Houck’s group excels in the design and optimization of superconducting circuits. De Leon’s laboratory specializes in quantum metrology, alongside the materials and fabrication methodologies that dictate qubit performance. Cava’s research group has dedicated decades to the development of superconducting materials. By combining their formidable strengths, the team achieved results unattainable by any single group working in isolation. Their success has already garnered considerable attention from the quantum computing industry.

Devoret emphasized the indispensable role of collaborations between academic institutions and commercial enterprises in advancing cutting-edge technologies. "There is a rather harmonious relationship between industry and academic research," he observed. University researchers are empowered to explore the fundamental boundaries of quantum performance, while industry partners can translate these discoveries into practical, large-scale systems.

"We’ve shown that it’s possible in silicon," de Leon stated. "The fact that we’ve shown what the critical steps are, and the important underlying characteristics that will enable these kinds of coherence times, now makes it pretty easy for anyone who’s working on scaled processors to adopt."

The seminal paper, "Millisecond lifetimes and coherence times in 2D transmon qubits," was published in Nature on November 5th. The author list includes Jeronimo G.C. Martinez, Paal H. Prestegaard, Basil M. Smitham, Atharv Joshi, Elizabeth Hedrick, Alex Pakpour-Tabrizi, Shashwat Kumar, Apoorv Jindal, Ray D. Chang, Ambrose Yang, Guangming Cheng, and Nan Yao, in addition to de Leon, Houck, Cava, Bahrami, and Bland. This pioneering research received primary support from the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, and the Co-design Center for Quantum Advantage (C2QA), with supplementary funding provided by Google Quantum AI.