Correction to: Nature Physics https://doi.org/10.1038/s41567-020-0995-5, published online 14 September 2020.

In the version of this Article originally published, in the Acknowledgements, the support from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 871124 (Laserlab-Europe) was mistakenly not mentioned; this information has now been added to the sentence beginning “This work was partially supported by...”. The online versions of the Article have been amended.