Fig. 1: Theoretical predictions for the polarization state of photons emitted by a radiative cascade.

a Bottom panel: sketch of the two emitting dipoles (blue and red arrows) with the respective isosurfaces of the radiation intensity. Top left panel: planar cut of the total emission pattern along with the direction of the electrical field oscillation for both dipole radiations, highlighting the intensity mismatch as well as the dependence of the orientation of both fields on the emission angle. Top right panel: overall degree of polarization (DOP), defined as the square root of the squared sum of the Stokes parameters (see the SI), as a function of the angles ϕ and θ. The dashed orange circle indicates a far-field region centered on the quantum emitter, corresponding to an emission angle up to θ_max. The dashed blue circles indicate different regions of θ values that select specific wavevectors. b Real part of the density matrix of the two-photon entangled state for two values of θ. The value of the concurrence for both angles is also reported. c Real part of the two-photon entangled state for two values of θ_max. The value of the concurrence for both angles is also reported.