Realization of a twin beam source based on four wave mixing in Cesium

Four-wave mixing (4WM) is a known source of intense non-classical twin beams. It can be generated when an intense laser beam (the pump) and a weak laser beam (the seed) overlap in a ð3Þ medium (here Cesium vapor), with frequencies close to resonance with atomic transitions. The twin beams generated by 4WM have frequencies naturally close to atomic transitions, and can be intense (gain 1) even in the CW pump regime, which is not the case for PDC ð2Þ phenomenon in nonlinear crystals. So, 4WM is well suited for atom-light interaction and atombased quantum-protocols. Here, we present the ¯rst realization of a source of 4-wave mixing exploiting D2 line of Cesium atoms.