  We experimentally demonstrate the nonclassical photon number correlations
expected in tripartite continuous variable states obtained by parametric
processes. Our scheme involves a single nonlinear crystal, where two
interlinked parametric interactions take place simultaneously, and represents a
bright and compact source of a sub-shot-noise tripartite light field. We
analyze the effects of the pump intensities on the numbers of detected photons
and on the amount of noise reduction in some details, thus demonstrating a good
agreement between the experimental data and a single-mode theoretical
description.
