  In this review article, we present a non-equilibrium quantum transport theory
for transient electron dynamics in nanodevices based on exact master equation
derived with the path integral method in the fermion coherent-state
representation. Applying the exact master equation to nanodevices, we also
establish the connection of the reduced density matrix and the transient
quantum transport current with the Keldysh nonequilibrium Green functions. The
theory enables us to study transient quantum transport in nanostructures with
back-reaction effects from the contacts, with non-Markovian dissipation and
decoherence being fully taken into account. In applications, we utilize the
theory to specific quantum transport systems, a variety of quantum decoherence
and quantum transport phenomena involving the non-Markovian memory effect are
investigated in both transient and stationary scenarios at arbitrary initial
temperatures of the contacts.
