Open-system nonequilibrium Green's functions and quantum transport in the transient regime

We present a generalization of the nonequilibrium Green's function formalism to the treatment of dynamically open systems, such as the active region of a modern small semiconductor structure. This approach relies on the partial-trace-free, time-convolutionless approach to the open-system reduced density matrix. We illustrate how one can analyse the short-time evolution of an open system within the present approach, and obtain corrections to the single-particle spectrum and level broadening.