A quantum-dot spin qubit with coherence limited by electrical noise and accuracy above 99.9%

A single-electron spin qubit achieved a phase coherence time of 20 μs and a control speed of up to 30 MHz.

• Enhanced quantum coherence has been observed despite challenges from background charge fluctuations in nanostructures.
• Free-evolution dephasing is attributed to charge noise rather than traditional magnetic noise, as indicated by a 1/f noise spectrum across seven decades of frequency.
• Single-qubit gate fidelities exceed 99.9% on average, suggesting high precision in qubit operations.
• The findings may contribute to the development of larger spin-qubit systems with improved fault tolerance.

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