QUANTUM LEAP FORWARD: TRANSMON QUBIT HITS MILESTONE

Researchers at Finland’s Aalto University have set a new benchmark in quantum computing, achieving a transmon qubit coherence time of one millisecond, nearly doubling the previous record of 0.6 milliseconds.

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Published in Nature Communications, the milestone, led by Ph.D. student Mikko Tuokkola under Dr. Yoshiki Sunada, marks a significant step toward practical quantum computers.

The team’s qubit, fabricated in Aalto’s Micronova cleanroom with superconducting film from VTT Technical Research Centre, maintained a median echo dephasing time of 0.5 milliseconds and a maximum of 1.057 milliseconds, surpassing prior benchmarks.

Coherence time, the duration a qubit retains its quantum state, is critical for error-free computations. Longer times allow more complex operations, reducing the need for resource-heavy error correction.

The team’s success, part of Finland's Quantum Flagship initiative, used refined niobium patterning, precise Josephson junction fabrication, and a traveling-wave parametric amplifier to cut noise, boosting Finland's reputation as a quantum powerhouse. This achievement could slash the overhead for faulttolerant systems, bringing quantum computing closer to real-world use.

The breakthrough, detailed in an arXiv preprint, comes as the $45 billion quantum computing market grows 30% annually. While the millisecond mark is a leap, challenges like scaling to multi-qubit systems and maintaining consistency across batches remain, testing the path to practical applications. The Aalto team’s success hinges on meticulous engineering. Transmon qubits, a leading platform for superconducting quantum computers, typically suffer from decoherence caused by material defects and environmental noise. The researchers optimized their approach with a tantalum-based platform, replacing niobium to reduce surface losses, and used electron-beam lithography for precise Josephson junctions—tiny superconducting tunnels critical for qubit function. Annealed sapphire substrates further cut dielectric losses, ensuring cleaner signals.