Coupling of four-wave mixing and Raman scattering by ground-state atomic coherence

We demonstrate coupling of light resonant to transition between two excited states of rubidium and long-lived ground-state atomic coherence. In our proof-of-principle experiment a nonlinear process of four-wave mixing is used to achieve light emission proportional to independently prepared ground-state atomic coherence. Strong correlations between stimulated Raman-scattering light heralding the generation of ground-state coherence and the four-wave mixing signal are measured and shown to survive the storage period, which is promising in terms of quantum memory applications. The process is characterized as a function of laser detunings.