In a significant advance toward functional, large-scale quantum computers, engineers have developed a new type of superconducting qubit that maintains its fragile quantum state for more than 1 millisecond. This breakthrough represents the largest single improvement in qubit coherence time in over a decade and is three times longer than the best previously reported laboratory results. The development directly addresses the most significant obstacle preventing current quantum processors from performing useful computations: the fleeting lifespan of their fundamental information-processing units.
The achievement is critical because a qubit’s lifespan, or “coherence time,” determines the number of quantum operations it can perform before its information is lost to environmental noise. The new design is nearly 15 times more stable than the qubits used in today’s most advanced commercial quantum processors. Developed by a team at Princeton University, the innovation is based on the widely used transmon architecture, making it compatible with existing systems built by industry leaders like Google and IBM. By building and validating a complete quantum chip with the new component, the researchers have cleared a key hurdle for developing fault-tolerant systems ready for industrial scaling.
The Quantum Decoherence Problem
The primary challenge holding back the quantum computing revolution is decoherence. Quantum bits, or qubits, store information in delicate quantum states that are easily disturbed by tiny fluctuations in their environment, such as temperature changes or electromagnetic fields. This interaction causes the qubit to lose its quantum properties in a process called decoherence, which corrupts the data and halts computations. For nearly a decade, progress in extending the coherence time of superconducting qubits had largely plateaued at around 100 microseconds for even the most advanced systems.
This short lifespan severely limits the complexity of problems that quantum computers can solve. Performing a useful calculation requires a long sequence of operations, and if the qubits decohere before the sequence is complete, the final result is unreliable. Overcoming this limitation is essential for implementing the sophisticated quantum error correction codes that will be necessary for building large, fault-tolerant machines. The Princeton team’s work marks a major departure from this plateau, pushing coherence times firmly into the millisecond range and reviving possibilities for rapid hardware advancement.
A Novel Materials Platform
The breakthrough is rooted in materials science and a re-evaluation of the transmon qubit’s physical construction. The transmon is the workhorse of the superconducting quantum computing industry, favored for its relative resistance to noise and its suitability for scalable designs. However, microscopic material defects and surface impurities have long been a source of decoherence that was difficult to eliminate. The Princeton researchers addressed this by building their qubit with a novel combination of materials, primarily tantalum and silicon.
This approach minimizes the material absorption and other loss pathways that drain energy from the qubit and cause it to decohere. Tantalum, a metallic element, has properties that make it highly suitable for superconducting circuits, while the team’s fabrication process appears to reduce the interfaces and contaminants that plague other designs. The result is a qubit that is not only more robust but is also built upon an architecture that is already well-understood and widely implemented, accelerating its potential for adoption.
Record-Breaking Performance Metrics
Achieving Millisecond Stability
In a paper published in the journal Nature, the research team reported a coherence time exceeding 1 millisecond. This figure is a threefold improvement over the previous laboratory record for a transmon qubit and a nearly fifteenfold improvement compared to the typical components in existing large-scale quantum processors. To verify the performance in a realistic setting, the engineers did not just create a single high-performance qubit; they integrated the design into a fully functional quantum chip and validated its operational stability. This step confirms that the qubit’s impressive lifespan is not merely a laboratory curiosity but a viable feature for complex, multi-qubit processors.
Defining a New Standard
The two key metrics for a qubit’s lifespan are its energy relaxation time (T1) and its dephasing time (T2). While the specific T1 and T2 values from the Princeton study were part of the detailed findings, the overall reported coherence of over 1 millisecond surpasses previous top-tier results that were typically below 400 microseconds. This leap is the most significant improvement in the field in more than ten years, setting a new benchmark for what is possible with superconducting circuits.
Implications for Scalable Quantum Computing
The immediate impact of a longer-lived qubit is the potential for dramatically more powerful quantum computers. Because the new design is compatible with existing transmon-based processors, it could be integrated into current systems to provide a substantial performance boost. The researchers estimate that swapping these new components into a state-of-the-art processor, such as Google’s Willow, could enhance its performance by a factor of 1,000.
Furthermore, the benefits of improved coherence grow exponentially as the number of qubits in a system increases. With more stable qubits, quantum processors can run deeper, more complex algorithms and implement the error-correction schemes needed for fault tolerance. This advance moves the technology from the current era of “noisy, intermediate-scale quantum” (NISQ) devices closer to the goal of practical, error-corrected machines capable of solving real-world problems in medicine, finance, and materials science.
The Research and Its Path Forward
The work was conducted by a team of engineers and scientists at Princeton University, with leadership from researchers including Andrew Houck, Nathalie de Leon, and Robert Cava. The project highlights a collaborative, interdisciplinary approach, combining quantum physics with materials science and engineering. This research received primary support from the U.S. Department of Energy through the Co-design Center for Quantum Advantage (C2QA), a national quantum information science research center, with partial support from Google Quantum AI. The successful demonstration of a millisecond-coherence qubit opens the door for further material refinements and fabrication techniques that could extend qubit lifespans even longer.