Correction to: Nature Photonics https://doi.org/10.1038/s41566-019-0437-z, published online 20 May 2019.

In the version of this Letter originally published online, in the sentence beginning “Here, we report a time-domain (τ) scheme”, ‘>5,000 ytterbium signal transducers’ should have read ‘about 5,000 ytterbium signal transducers’. And in the graph labelled ‘Downshifting’ in Fig. 1d the red peak was labelled ‘Em.’; instead it should have been labelled ‘Ex.’ These errors have now been corrected in all versions.