Entangled photon pairs from a quantum dot cascade decay: the effect of time-reordering

Coulomb interactions between confined carriers remove degeneracies in the excitation spectra of quantum dots. This provides a which path information in the cascade decay of biexcitons, thus spoiling the energy-polarization entanglement of the emitted photon pairs. We theoretically analyze a strategy of color coincidence across generation (AG), recently proposed as an alternative to the previous, within generation (WG) approach. We simulate the system dynamics and compute the correlation functions within the density-matrix formalism. This allows to estimate quantities that are accessible by a polarization-tomography experiment, and that enter the expression of the two-photon concurrence. We identify the optimum parameters within the AG approach, and the corresponding maximum values of the concurrence.