The isolation of qubits from noise sources, such as surrounding nuclear spins and spin–electric susceptibility1,2,3,4, has enabled extensions of quantum coherence times in recent pivotal advances towards the concrete implementation of spin-based quantum computation. In fact, the possibility of achieving enhanced quantum coherence has been substantially doubted for nanostructures due to the characteristic high degree of background charge fluctuations5,6,7. Still, a sizeable spin–electric coupling will be needed in realistic multiple-qubit systems to address single-spin and spin–spin manipulations8,9,10. Here, we realize a single-electron spin qubit with an isotopically enriched phase coherence time (20 μs)11,12 and fast electrical control speed (up to 30 MHz) mediated by extrinsic spin–electric coupling. Using rapid spin rotations, we reveal that the free-evolution dephasing is caused by charge noise—rather than conventional magnetic noise—as highlighted by a 1/f spectrum extended over seven decades of frequency. The qubit exhibits superior performance with single-qubit gate fidelities exceeding 99.9% on average, offering a promising route to large-scale spin-qubit systems with fault-tolerant controllability.
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We thank the Microwave Research Group in Caltech for technical support. This work was supported financially by Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST) (JPMJCR15N2, JPMJCR1675) and the ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan). J.Y., T.N. and T.O. acknowledge support from RIKEN Incentive Research Projects. T.O. acknowledges support from Precursory Research for Embryonic Science and Technology (PRESTO) (JPMJPR16N3), JSPS KAKENHI grant numbers JP16H00817 and JP17H05187, Advanced Technology Institute Research Grant, the Murata Science Foundation Research Grant, Izumi Science and Technology Foundation Research Grant, TEPCO Memorial Foundation Research Grant, The Thermal and Electric Energy Technology Foundation Research Grant, The Telecommunications Advancement Foundation Research Grant, Futaba Electronics Memorial Foundation Research Grant and Foundation for Promotion of Material Science and Technology of Japan (MST) Foundation Research Grant. T.K. acknowledges support from Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (JSPS KAKENHI) grant numbers JP26709023 and JP16F16806. K.M.I. acknowledges support from KAKENHI (S) grant number JP26220602 and JSPS Core-to-Core Program. S.T. acknowledges support by JSPS KAKENHI grant numbers JP26220710 and JP16H02204.
Supplementary Text and Figures 1–3