Directional photon transfer between two wires.

The directional transfer of a single photon from one wire to another, leaving all other neighbor states unaffected, is of great importance. We present a simple coupling structure that makes such transfer possible, for anygiven photon wavelength and linewidth. We give closed-form expressions for the parameters necessary to build such a structure. An illustration of our analytic study is given for the directional transmission of a telecommunication signal between two lines.