Induced coherence via spontaneous and stimulated four-wave mixing processes from two atomic ensembles

In the context of wave-particle duality, induced-coherence experiments were understood through the lens of which-path information as a means of realizing complementarity [1-4]. In this work, we report on the induced coherence of two-mode squeezed coherent states using a double-path interferometer that consists of two independent four-wave mixing (FWM) atomic ensembles. These atomic ensembles are generated via spontaneous and stimulated independent FWM processes from a warm atomic ensemble of 87Rb. We measured single-photon interferences and auto-correlation functions from a two-mode squeezed vacuum state to coherent states, based on the average photon number of the stimulating laser. Our results demonstrate the ability to distinguish between two-mode squeezed vacuum and coherent states. Furthermore, our experimental scheme, which employs two FWM atomic ensembles with long-coherent photons, is an excellent method for understanding the complementarity of induced coherence in which-path information.