  Quantum probabilities are defined for several important physical cases
characterizing measurements with multimode quantum systems. These are the
probabilities for operationally testable measurements, for operationally
uncertain measurements, and for entangled composite events. The role of the
prospect and state entanglement is emphasized. Numerical modeling is presented
for a two-mode Bose-condensed system of trapped atoms. The interference factor
is calculated by invoking the channel-state duality.
