Correction to: Nature Physics https://doi.org/10.1038/s41567-020-0952-3, published online 6 July 2020.

In this Letter the following original sentence has been amended for clarity: “As the Kramers theorem does not hold in the presence of a non-zero weak-link phase bias φ, the splitting of the spin states requires an additional ingredient.”; it has been changed to: “Although the presence of a non-zero weak-link phase bias φ breaks time-reversal symmetry so that the Kramers theorem does not hold, this alone is insufficient to lift the spin degeneracy—an additional effect is required.” The online versions of the Letter have been amended.