https://phys.org/news/2025-07-asymmetric-metasurface-precise-photon-entanglement.html

created by a #metasurface made of indium gallium phosphide (InGaP), which has a nonlinear response that can split a classical photon into two #quantumphotons. By tuning the wavelength of the initial photon, the two new photons can be generated as fully entangled through their polarization, not entangled at all, or any value in between, with picosecond control.