Non-Classical Correlated Photon Pairs Generation via Cascade Transition of 5S_1/2–5P_3/2–5D_5/2 in a Hot ⁸⁵Rb Atomic Vapor

We experimentally prepare the non-classical correlated photon pairs at the wavelengths of 780 and 776 nm via the cascade transition of 5S_1/2–5P_3/2–5D_5/2 in a hot ⁸⁵Rb atomic ensemble. By measuring the function of cross-correlation and auto-correlation of photons, a violation of Cauchy–Schwarz inequality by a factor of 283 is obtained, which clearly indicates a strong non-classical correlation between the generated photons. We also find that noise photons scattered from pump lasers have a strong effect on the Cauchy–Schwarz inequality factor by changing the intensity of the pump laser, the experimental results are consistent with the theoretical predictions.