Nature Nanotechnology 8, 561–564 (2013); published online 23 June 2013; corrected after print 26 September 2013.

In the version of this Letter originally published, ref. 21 should have read: Morley, G. W. et al. Quantum control of hybrid nuclear–electronic qubits. Nature Mater. 12, 103–107 (2013). This error has been corrected in the HTML and PDF versions of the Letter.