  We theoretically demonstrate coherent control over propagation of surface
plasmon polaritons(SPP), at both telecommunication and visible wavelengths, on
a metallic surface adjacent to quantum coherence (phaseonium) medium composed
of three-level quantum emitters (semiconductor quantum dots, atoms, rare-earth
ions, etc.) embedded in a dielectric host. The coherent drive allows us to
provide sufficient gain for lossless SPP propagation and also lowers the
pumping requirements. In case of lossy propagation, an order of magnitude
enhancement in propagation length can be achieved. Optical control over SPP
propagation dynamics via an external coherent drive holds promise for quantum
control in the field of nanophotonics.
