Collision-induced constructive quantum interference

We theoretically study the collision-induced constructive quantum interference in an open four-level system with the density-matrix approach based on the experimental observation of constructive quantum interference between two transition pathways 3P(1/2)-5S (or 4D) and 3P(3/2)-5S (or 4D) via equal-frequency hybrid excitation in the Na-2-Na system. The effects of the collision-induced coherent and incoherent decay rates and the ratio of the two transition dipole moments on the interference are analyzed. It is shown that through the incoherent process (collision), the coherence between a widely separated doublet and subsequent constructive quantum interference can be realized. The physical origin of the constructive interference can be seen clearly in the dressed-atom picture. The theoretical results can also be used to qualitatively explain the dependence of quantum interference on the experimental buffer gas pressure and sample temperature.