Driven Open Quantum Systems

This chapter considers an open quantum system, exemplified by a junction made up of a central region of finite size and of (at least two) connected terminals, with a time-dependent bias superposed on the terminals. For simplicity, fermions in the terminals are assumed to be noninteracting, while those in the central region are interacting. In particular, the time-dependent current flowing through the system is calculated using the Schwinger–Keldysh formalism developed in Part I for the normal phase. To this end, the present problem is framed in a more general context by adapting the Zwanzig P-Q projector operators technique. In this way, “memory” effects arise due to the transfer of information from P to Q subspaces (and vice versa).