Two-photon emission from a superlattice-based superconducting light-emitting structure. S. Bouscher, D. Panna, R. Jacovi, F. Jabeen, C. Schneider, S. Höfling and A. Hayat in Light: Sci. \& App. 13:135 (2024).  What the paper says!?

This paper reports on two-photon emission from a superlattice superconducting structure, where Cooper pairs are injected in a hybrid «superconducting light-emitting diode (SLED)» where the superconductor is coupled to a semiconductor PN junction:

This, according to the Authors, results in emission of two photons:

we observe, for the first time, clear features which can be directly attributed to the two-photon

nature of the emission

One evidence they have for this is a very small increase of $g^{(2)}$ (they discuss other smoking guns):

Besides the data is not particularly convincing, with very small deviations from no-correlation, two-photon emission is not well characterized by $g^{(2)}$ anyway.

I haven't read the paper in detail. It was passed to me by Daniele Sanvitto as an interesting work.