Correction to: Nature Physics https://doi.org/10.1038/s41567-019-0747-6, published online 13 January 2020.

In the version of this Article originally published online, in the Acknowledgements, the support from the MITRE Quantum Moonshot Program was mistakenly not mentioned; this information has now been added to the sentence beginning “This work was supported by...”. All versions of the Article have been amended.