Nature Physics 4, 120–124 (2008); published online 9 December 2007; corrected after print 8 April 2014.

In the version of this Letter originally published, discussions of SNS and NSN transistors were reversed in the captions of Figs 1–3, with concomitant errors in the main text where those figures were referred to. The following text should have been in the caption of Fig. 1: 'In the SNS turnstile, the roles of aluminium and copper are swapped, that is the leads are superconducting and the island is normal-state.' The sentence at the top of the right column on page 123 proclaiming the absence of the parity effect in the measured SNS transistor should not have been included as the parity effect can only manifest in an NSN transistor. These errors have been corrected in the online versions of the Letter.