  The dynamics of a quantum system, undergoing unitary evolution and continuous
monitoring, can be described in term of quantum trajectories. Although the
averaged state fully characterises expectation values, the entire ensamble of
stochastic trajectories goes beyond simple linear observables, keeping a more
attentive description of the entire dynamics. Here we go beyond the Lindblad
dynamics and study the probability distribution of the expectation value of a
given observable over the possible quantum trajectories. The measurements are
applied to the entire system, having the effect of projecting the system into a
product state. We develop an analytical tool to evaluate this probability
distribution at any time t. We illustrate our approach by analyzing two
paradigmatic examples: a single qubit subjected to magnetization measurements,
and a free hopping particle subjected to position measurements.
