Correction to: Communications Physics, published online 7 January 2019.

The second author of this manuscript has been designated as the corresponding author, and their contact details have been added to both the PDF and HTML versions of the Article.

The section “Corresponding author” has been changed to: Correspondence to Fan Xu or Yuan-Qing Wang in the HTML version of the article.

The correspondence footnote at the bottom of page 1 in the PDF version of the manuscript has been changed to Correspondence and requests for materials should be addressed to F.X. (email: or to Y.-Q.W. (email: