Fig. 4: Two-photon state and entanglement figures of merit as a function of the collection aperture for a CBR quantum dot.
From: Wavevector-resolved polarization entanglement from radiative cascades
a Fidelity to the \(\left\vert {\phi }^{+}\right\rangle\) state and concurrence as a function of different sizes of the collection region centered around the main propagation axis. Data are shown as a function of the corresponding collection half-angle θmax. b Experimental density matrices corresponding to different values of θmax, showing how the two-photon polarization state follows the description of Eq. (6). Error bars in the experimental data are computed assuming Poissonian distributions of coincidences (they are remarkably small due to the high number of recorded events).
