Quantum plasmonics relies on a new paradigm for light-matter interaction. It benefits from strong confinement of surface plasmon polaritons (SPP) that ensures efficient coupling at a deep subwavelength scale, instead of working with a long lifetime cavity polariton that increases the duration of interaction. The large bandwidth and the strong confinement of one dimensional SPP enable controlled manipulation of a nearby quantum emitter. This paves the way to ultrafast nanooptical devices. However, the large SPP bandwidth originates from strong losses so that a clear understanding of the coupling process is needed. In this report, we investigate in details the coupling between a single emitter and a plasmonic nanowire, but also SPP mediated coupling between two emitters. We notably clarify the role of losses in the Purcell factor, unavoidable to achieve nanoscale confinement down to 10(-4)(λ/n)(3). Both the retarded and band-edge quasi-static regimes are discussed.