Generating quantum correlated twin beams by four-wave mixing in hot cesium vapor

Using a nondegenerate four-wavemixing process based on a double-A scheme in hot cesium vapor, we generate quantum correlated twin beams with a maximum intensity-difference squeezing of 6.5 dB. The substantially improved squeezing can be mainly attributed to very good frequency and phase-difference stability between the pump and probe beams in our experiment. Intensity-difference squeezing can be observed within a wide experimental parameter range, which guarantees its robust generation. Since this scheme produces multi-spatialmode twin beams at the Cs D-1 line, it is of interest for experiments involving quantum imaging and coherent interfaces between atomic and solid-state systems.