4. Conclusions
This paper highlights some observations that may be interesting to pursue in future applications of entangled photons from single atoms and molecules. Against questions raised regarding applicability of Bell’s inequalities, and of two-photon correlation results in parametric down-conversion experiments, data from the first visible-light entangled photon experiment from single atoms were reanalyzed. The polarization photon correlation anisotropy (A) is proposed as a discrimination tool: A is found close to 1, as predicted quantum mechanically, and well above the interval 0 A½ of local realism models based on classical fields. The maximum difference between correlations based on physical field models for quantum and semi-classical theories is expected to be found at parallel and perpendicular polarizer orientations, in contrast to what is usually assumed optimal in Bell tests. Whereas parametric down-conversion-produced light is Poissonian, pairs of entangled photons emerging from single atoms are isolated, with non-Poissonian distribution. Similarly, artificial atom quantum dots, and most likely molecules too, have the advantage of producing non-Poissonian entangled photons. A shape difference is noticed in the time-resolved correlation spectrum suggesting that entangled photons may exhibit a more symmetric coincidence spectrum compared to the clearly asymmetric photon distribution in absence of polarizers as a result of delayed fluorescence of the intermediate state. Finally, entangled photon-interactions with molecules are suggested a potentially interesting new research field, with applications to both absorption and emission of entangled photon pairs, for analytical purposes and as sources of entangled light, respectively.
