Princeton engineers have achieved a groundbreaking advancement in quantum computing with the development of a superconducting qubit that boasts a coherence time three times longer than the most robust designs currently available, marking a significant stride toward building reliable and powerful quantum computers. This pivotal improvement addresses one of the most formidable challenges in the field: the ephemeral nature of quantum information, a limitation that has historically hindered the realization of practical quantum computing. Andrew Houck, a leading figure in national quantum research and Princeton’s dean of engineering, articulated the critical nature of this breakthrough, 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 implications of this enhanced qubit stability are profound, promising to accelerate the development of quantum machines capable of tackling complex problems currently beyond the reach of even the most powerful supercomputers.

Published on November 5th in the prestigious journal Nature, the Princeton team’s research details a qubit that maintains its quantum state, or coherence, for an astonishing duration exceeding 1 millisecond. This remarkable achievement is triple the longest coherence time previously documented in laboratory experiments and a staggering fifteen times greater than the typical coherence times found in industrial quantum processors. To validate their findings, the researchers meticulously constructed a functional quantum chip incorporating their novel qubit design. This experimental validation demonstrated not only the qubit’s enhanced stability but also its capacity to support essential error correction mechanisms and its scalability towards larger, more complex quantum systems. The compatibility of their qubit architecture with those employed by industry giants like Google and IBM is particularly noteworthy. Their analysis projects that integrating Princeton’s design into Google’s existing Willow processor could yield a performance increase of up to 1,000-fold. Furthermore, Houck emphasized that the advantages of this design escalate exponentially as the number of qubits in a quantum system increases, underscoring its potential for transformative impact on the future of computing.

The promise of quantum computers lies in their ability to revolutionize fields ranging from drug discovery and materials science to financial modeling and artificial intelligence by solving problems intractable for classical computers. However, the current limitations of quantum computing are largely dictated by the inherent fragility of qubits. Before complex calculations can be completed, qubits often lose their delicate quantum information, a phenomenon known as decoherence. Therefore, extending qubit coherence times is paramount for the development of practical and error-resistant quantum hardware. Princeton’s recent breakthrough represents the most substantial single improvement in qubit coherence time observed in over a decade, signaling a potential paradigm shift in the field.

While numerous research groups worldwide are exploring diverse qubit technologies, Princeton’s innovation builds upon the widely adopted and well-understood transmon qubit architecture. Transmons, which function as superconducting circuits maintained at extremely low temperatures, are favored for their inherent resistance to environmental noise and their compatibility with established manufacturing processes. Despite these advantages, enhancing the coherence times of transmon qubits has presented a persistent and formidable challenge. Recent investigations, including those from Google, have identified material defects as the primary impediment to further performance gains in their most advanced processors.

Addressing these material-related hurdles, the Princeton team devised a sophisticated two-pronged strategy. Their innovative approach first involved the integration of tantalum, a metal renowned for its ability to minimize energy dissipation in sensitive electronic circuits. The second critical component of their strategy was the substitution of the conventional sapphire substrate with high-purity silicon, a material that forms the bedrock of the modern semiconductor industry. The successful direct growth of tantalum on silicon necessitated overcoming intricate technical challenges related to material interfacial interactions. However, the researchers not only surmounted these obstacles but also discovered substantial performance benefits in the process. Nathalie de Leon, co-director of Princeton’s Quantum Initiative and a co-principal investigator on the project, highlighted the dual advantages of their tantalum-silicon design: superior performance and simplified large-scale manufacturing. "Our results are really pushing the state of the art," she remarked.

Michel Devoret, chief scientist for hardware at Google Quantum AI and a recipient of the 2025 Nobel Prize in Physics, acknowledged the extreme difficulty of extending the lifespan of quantum circuits, characterizing the pursuit as a "graveyard" of attempted solutions. He lauded de Leon’s tenacity, stating, "Nathalie really had the guts to pursue this strategy and make it work." The research project received primary funding from the U.S. Department of Energy National Quantum Information Science Research Centers and the Co-design Center for Quantum Advantage (C2QA), an initiative led by Houck from 2021 to 2025. The paper, titled "Millisecond lifetimes and coherence times in 2D transmon qubits," lists postdoctoral researcher Faranak Bahrami and graduate student Matthew P. Bland as co-lead authors.

The enhanced stability of qubits, as demonstrated by Princeton’s new design, is directly correlated with the overall capability of a quantum computer. Houck explained that a quantum computer’s power is a function of two key factors: the number of interconnected qubits and the number of operations each qubit can perform before accumulating significant errors. By improving the durability of individual qubits, both of these factors are strengthened. Longer coherence times directly facilitate system scaling and enable more robust error correction, two indispensable elements for practical quantum computing. Energy loss is the predominant cause of qubit failure, often stemming from microscopic surface defects in metallic components that trap energy and disrupt quantum computations. These disruptions are amplified as more qubits are integrated into a system. Tantalum’s inherent advantage lies in its significantly lower propensity for such defects compared to commonly used metals like aluminum. This reduction in defects leads to fewer errors and a simplified process for correcting the remaining ones.

Houck and de Leon first introduced tantalum for superconducting chips in 2021, an endeavor that benefited from the expertise of Princeton chemist Robert Cava, a renowned specialist in superconducting materials. Cava’s interest in the problem was sparked by a presentation from de Leon, leading to discussions that culminated in his suggestion of tantalum as a promising candidate. "Then she went and did it," Cava remarked. "That’s the amazing part." Their initial collaboration with Cava’s group resulted in a tantalum-based superconducting circuit fabricated on a sapphire substrate, which demonstrated a significant increase in coherence time, nearing previous world records. Bahrami further elaborated on tantalum’s exceptional properties, emphasizing its extreme durability and resistance to the rigorous cleaning protocols essential for contaminant removal during fabrication. "You can put tantalum in acid, and still the properties don’t change," she noted.

Subsequent analysis revealed that the sapphire substrate was a major contributor to the remaining energy losses. The switch to a high-purity silicon substrate effectively eliminated this source of loss. The synergistic combination of tantalum and silicon, coupled with refined fabrication techniques, yielded one of the most substantial improvements ever recorded for a transmon qubit. Houck aptly described the outcome as "a major breakthrough on the path to enabling useful quantum computing." He further underscored the exponential benefits of this design for larger systems, projecting that replacing current industry-leading qubits with Princeton’s version could render a theoretical 1,000-qubit computer approximately 1 billion times more effective.

The success of this project is a testament to the power of interdisciplinary collaboration, drawing upon three distinct areas of expertise: Houck’s group, which specializes in the design and optimization of superconducting circuits; de Leon’s lab, focused on quantum metrology and the materials and fabrication processes crucial for qubit performance; and Cava’s group, with its decades of experience in developing advanced superconducting materials. This synergistic approach allowed the team to achieve results that would have been unattainable by any single group. The groundbreaking nature of their findings has already garnered significant attention from the quantum industry.

Devoret emphasized the indispensable role of collaborations between academic institutions and industrial partners in propelling advanced technologies forward, observing a "rather harmonious relationship between industry and academic research." He explained that university researchers are well-positioned to explore the fundamental limits of quantum performance, while industry partners can then leverage these discoveries for the development of large-scale systems. "We’ve shown that it’s possible in silicon," de Leon affirmed. "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 research, published in Nature, 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 partial support from Google Quantum AI. 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 the previously mentioned Houck, de Leon, Cava, Bahrami, and Bland.