  Disentanglement of a laser source from its target qubit is proposed as a
criterion establishing the laser quantum state as a coherent state. It is shown
that the source-target density operator has a unique factorization in coherent
states when the environmental record monitoring laser pump quanta is ignored.
The source-target state conditioned upon the complete environmental record is
entangled, though, as a state of known total quanta number (source plus
target).
