  Recent advances towards spin-based quantum computation have been primarily
fuelled by elaborate isolation from noise sources, such as surrounding nuclear
spins and spin-electric susceptibility, to extend spin coherence. In the
meanwhile, addressable single-spin and spin-spin manipulations in
multiple-qubit systems will necessitate sizable spin-electric coupling. Given
background charge fluctuation in nanostructures, however, its compatibility
with enhanced coherence should be crucially questioned. Here we realise a
single-electron spin qubit with isotopically-enriched phase coherence time (20
microseconds) 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 (instead of conventional
magnetic) noise featured by a 1/f spectrum over seven decades of frequency. The
qubit nevertheless exhibits superior performance with single-qubit gate
fidelities exceeding 99.9% on average. Our work strongly suggests that
designing artificial spin-electric coupling with account taken of charge noise
is a promising route to large-scale spin-qubit systems having fault-tolerant
controllability.
