Physicists at Aalto University (Finland) have set a new world record for the duration of the coherent state of a superconducting qubit, the core of a quantum computer. They achieved a maximum coherence time of 1 millisecond, with a median value of 0.5 milliseconds. This value is significantly higher than previous values, which rarely reached 0.6 milliseconds and were usually unstable.
In quantum computing, even fractions of a millisecond matter. The longer a qubit remains in a coherent quantum state, the more operations a quantum computer can perform before errors occur. As the authors of the study point out , these advances are important not only for quantum computing, but also for the development of quantum sensors and simulators.
The key to success lies in improved design and materials. The researchers have created a new type of transmon qubit, a noise-resistant type of superconducting qubit widely used in modern quantum technology. They used ultrapure superconducting films and manufactured the chip in a sterile environment. The circuit elements were etched using electron beam lithography, and the Josephson junctions, responsible for quantum behavior, were produced with high precision.
Particular attention was paid to material purity and protection from oxidation. Even microscopic defects can prematurely destroy the quantum state. The chip was cooled to a temperature close to absolute zero in a dilution refrigerator, then a special amplifier was used to read the signals without distortion.
Of the four qubits on the chip, one, called Q2, showed particularly remarkable performance. It has consistently achieved sub-millisecond coherence in repeated experiments, confirming the robustness of the technique. Similar results have already been demonstrated by researchers who managed to make superconducting qubits retain information 10 times longer than normal.
While the result represents a major step forward, scalability remains a challenge. Ensuring stable coherence across hundreds or thousands of transmon qubits on a single chip is much more difficult than with a single instance. However, the authors have openly published full details of the technique, including circuits, parameters, and measurement protocols, so that other research groups can replicate and consolidate this success.
The research is published in the journal Nature Communications and could bring quantum technologies closer to practical real-world applications.
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