  We present an efficient approach, based on a number-conditioned master
equation, for large-deviation analysis in mesoscopic transports. Beyond the
conventional full-counting-statistics study, the large-deviation approach
encodes complete information of both the typical trajectories and the rare
ones, in terms of revealing a continuous change of the dynamical phase in
trajectory space. The approach is illustrated with two examples: (i) transport
through a single quantum dot, where we reveal the inhomogeneous distribution of
trajectories in general case and find a particular scale invariance point in
trajectory statistics; and (ii) transport through a double dots, where we find
a dynamical phase transition between two distinct phases induced by the Coulomb
correlation and quantum interference.
