A device including an input port configured to receive an input signal is described. The device also includes an output port and a structure, which structure includes a tunneling junction connected with the input port and the output port. The tunneling junction is configured in a way (i) which provides electrons in a particular energy state within the structure, (ii) which produces surface plasmons in response to the input signal, (iii) which causes the structure to act as a waveguide for directing at least a portion of the surface plasmons along a predetermined path toward the output port such that the surface plasmons so directed interact with the electrons in a particular way, and (iv) which produces at the output port an output signal resulting from the particular interaction between the electrons and the surface plasmons.