Correction to: Nature Photonics, published online 13 April 2020.

In the version of this Review Article originally published online, references 6 and 15 were duplicates: “Somaschi, N. et al. Near-optimal single-photon sources in the solid state. Nat. Photon. 10, 340–345 (2016).” Reference 15 has now been replaced with “Ding, X. et al. On-demand single photons with high extraction efficiency and near-unity indistinguishability from a resonantly driven quantum dot in a micropillar. Phys. Rev. Lett. 116, 020401 (2016).” All versions of the Review Article have been amended.