Correction to: Nature, published online 13 September 2017.

In Fig. 2b of this Review, two of the gates were inadvertently swapped. At the top right, ‘Xa+c’ should have been ‘Zb’, and at the bottom right ‘Zb’ should have been ‘Xa+c’. Fig. 2b has been corrected online. The Supplementary Information of this Author Correction contains the original, incorrect Fig. 2b, for transparency.

Supplementary Information is available in the online version of this Amendment.