Nature Photonics 11, 247–251 (2017); published online 27 March 2017; corrected after print 14 August 2017.

In the version of this Article originally published, in Fig. 3c, in the y axis label, the units '(c.p.s.)' should not have been included; the label should have read “Dark counts”. This has now been corrected in the online versions of the Article.