Correction to: Nature Physics https://doi.org/10.1038/s41567-021-01259-3, published online 3 June 2021.

In the version of this News & Views article originally published online, the reference originally cited in the sentence beginning “An ultra-intense laser pulse reflected from...” was incorrect; the correct reference should have been to “Vincenti, H. Phys. Rev. Lett. 123, 105001 (2019)”, which wasn’t originally included and has now been added as ref. 6. Subsequent references have been renumbered. In addition, in the sentence beginning “This may enable approaching the Schwinger limit...”, refs. 7 and 8 should have been cited instead of just ref. 7. All versions of the article have been amended.