Manipulating photonic signals by a multipurpose quantum junction.

We show that photon wave packets can be manipulated and reshaped in various ways by a quantum junction comprising a set of three-level atoms coupling two waveguides. We consider atomic nodes with the $\Lambda$-scheme of allowed optical transitions, one of which is driven by an external classical control field. Addressing the dynamics of wave packets in such a system, we demonstrate that a photon pulse can be either stored partially in the junction, delayed by a controlled time, split into several parts, or routed into one of the selected output channels. We argue, therefore, that our proposed design is a promising prototype of a multipurpose quantum junction.