  Using a nondegenerate four-wave mixing process based on a double-$\Lambda$
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-spatial-mode 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.
