Imroatul Nasiyah
Princeton engineers have engineered a superconducting qubit that exhibits three times the stability of the most robust designs currently available, marking a significant stride toward the realization of reliable and powerful quantum computers. This breakthrough addresses the critical bottleneck in quantum computing: the ephemeral nature of qubit information, which severely limits the duration and complexity of calculations that can be performed. Andrew Houck, a leading figure in national quantum research and Princeton’s dean of engineering, emphasized the profound implications 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."
The groundbreaking research, detailed in a Nov. 5 publication in the prestigious journal Nature, reveals that the Princeton team’s qubit can maintain its quantum state, or coherence, for over 1 millisecond. This duration is a remarkable triple of the longest lifetimes previously documented in laboratory settings and an impressive fifteen times greater than the coherence times typical of industrial quantum processors. To validate their findings, the researchers constructed a functional quantum chip utilizing their novel qubit design, demonstrating its capacity for error correction and its scalability towards larger quantum systems. Crucially, this new qubit architecture is compatible with the foundational designs employed by major quantum computing players like Google and IBM. The Princeton team’s analysis suggests that integrating their approach into Google’s Willow processor could yield a thousandfold increase in performance. Houck further elaborated that the benefits of this design amplify exponentially as the number of qubits in a quantum system increases.
The immense promise of quantum computers lies in their ability to tackle problems intractable for even the most powerful classical computers. However, their current practical utility is hampered by the tendency of qubits to lose their delicate quantum information before complex computations can be completed. Extending qubit coherence time is therefore paramount for the development of practical quantum hardware. The improvement achieved by Princeton represents the most substantial single gain in coherence time observed in over a decade, signaling a new era of progress.
While numerous research institutions 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 favored for their inherent resistance to environmental noise and their compatibility with existing semiconductor manufacturing techniques. Despite these advantages, significantly extending the coherence time of transmon qubits has presented a formidable challenge. Recent findings from Google, for instance, indicated that material defects have become the primary impediment to advancing their latest processor designs.
To surmount these material-related obstacles, the Princeton team devised a two-pronged materials strategy. The first key element was the incorporation of tantalum, a metal renowned for its ability to help delicate electronic circuits retain energy. The second crucial innovation involved substituting the conventional sapphire substrate with high-purity silicon, a material that forms the bedrock of the modern computing industry. The direct growth of tantalum on silicon presented a series of intricate technical hurdles related to the material interface, which the researchers successfully navigated, uncovering substantial advantages in the process. Nathalie de Leon, co-director of Princeton’s Quantum Initiative and co-principal investigator on the project, highlighted that their tantalum-silicon design not only surpasses prior approaches in performance but also offers a simpler manufacturing pathway for large-scale production. "Our results are really pushing the state of the art," she remarked.
Michel Devoret, chief scientist for hardware at Google Quantum AI and a partial funder of the research, lauded the team’s achievement, acknowledging the notorious difficulty of extending the operational lifetime of quantum circuits. He described the pursuit of this goal as having been a "graveyard" of abandoned attempts. Devoret, a recipient of the 2025 Nobel Prize in Physics, specifically praised de Leon’s perseverance, stating, "Nathalie really had the guts to pursue this strategy and make it work." The project received its primary financial backing from the U.S. Department of Energy’s National Quantum Information Science Research Centers and the Co-design Center for Quantum Advantage (C2QA), a center formerly directed by Houck and where he currently serves as chief scientist. The research paper credits postdoctoral researcher Faranak Bahrami and graduate student Matthew P. Bland as co-lead authors.
The capability of a quantum computer is fundamentally dictated by two primary factors: the total number of qubits that can be interconnected and the number of operations each qubit can perform before accumulated errors render the computation unreliable. Enhancing the durability of individual qubits directly bolsters both of these critical aspects. Longer coherence times directly enable greater scalability and more robust error correction. Energy loss is identified as the most prevalent source of failure in these sensitive quantum systems. Microscopic surface imperfections within the metallic components can trap energy, thereby disrupting the qubit’s state during calculations. These disruptions tend to multiply as more qubits are integrated into a system. Tantalum’s inherent advantage lies in its significantly lower concentration of such defects compared to commonly used metals like aluminum. A reduction in defects translates to fewer computational errors and a simplified process for correcting the remaining ones.
Houck and de Leon initially proposed the use of tantalum for superconducting chips in 2021, a concept that gained momentum with the expertise of Princeton chemist Robert Cava, a distinguished professor specializing in superconducting materials. Cava became engaged with the challenge after attending one of de Leon’s presentations, and their subsequent discussions led him to identify tantalum as a highly promising candidate material. "Then she went and did it," Cava commented, underscoring the significance of de Leon’s successful implementation. Researchers across all three involved laboratories embraced this idea, constructing a tantalum-based superconducting circuit on a sapphire substrate, which yielded a substantial improvement in coherence time, nearing the previous world record. Bahrami pointed out that tantalum’s exceptional durability is another key advantage, as it can withstand the rigorous cleaning processes required to eliminate contamination during fabrication. "You can put tantalum in acid, and still the properties don’t change," she noted.
Following the meticulous removal of contaminants, the team meticulously analyzed the remaining energy losses. Their investigation revealed that the sapphire substrate was the principal contributor to these residual issues. The strategic decision to transition to a high-purity silicon substrate effectively eliminated this source of energy loss. The synergistic combination of tantalum and silicon, coupled with refined fabrication techniques, culminated in one of the most significant advancements ever achieved in transmon qubit performance. Houck characterized the outcome as "a major breakthrough on the path to enabling useful quantum computing." He further projected that due to the exponential nature of the design’s benefits as systems scale, replacing current industry-leading qubits with the Princeton variant could empower a theoretical 1,000-qubit computer to operate approximately one billion times more effectively.
The success of this pioneering project is a testament to the synergistic collaboration drawing from three distinct areas of expertise. Houck’s group provided its deep knowledge in the design and optimization of superconducting circuits. De Leon’s laboratory contributed its specialization in quantum metrology, alongside critical insights into the materials and fabrication methods that govern qubit performance. Cava’s renowned group brought decades of experience in the development of superconducting materials. By converging their formidable strengths, the team achieved results that would have been unattainable by any single group in isolation. This groundbreaking achievement has already garnered considerable attention from the quantum computing industry.
Devoret emphasized the indispensable role of collaborations between academic institutions and industrial partners in propelling advanced technologies forward. He described the relationship between industry and academic research as "rather harmonious," where university researchers can rigorously investigate the fundamental limits of quantum performance, while industry partners can then translate these discoveries into large-scale, practical systems. "We’ve shown that it’s possible in silicon," de Leon stated, highlighting the accessibility of their findings for broader adoption. "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, titled "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 significant research was primarily supported by the U.S. Department of Energy’s Office of Science, National Quantum Information Science Research Centers, and the Co-design Center for Quantum Advantage (C2QA), with additional partial support from Google Quantum AI.
