  We theoretically study the dissipative dynamics of a quantum emitter placed
near the planar surface of a metal supporting surface plasmon excitations. The
emitter-metal coupling regime can be tuned by varying some control parameters
such as the qubit-surface separation and/or the detuning between characteristic
frequencies. By using a Green's function approach jointly with a
time-convolutionless master equation, we analyze the non-Markovian dissipative
features on the qubit time evolution in two cases of interest: i) an undriven
qubit initially prepared in its excited state and ii) the evolution towards a
steady-state for a system driven by a laser field. For weak to moderate
qubit-metal coupling strength, and on timescales large compared to the surface
plasmon oscillation time, a Markovian approximation for the master equation
results to be adequate to describe the qubit main optical properties: surface
enhancements of rate emission, optical spectra and time-dependent photon-photon
correlation functions. The qubit decay shows a crossover passing from being
purely dissipative for small qubit-surface distances to plasmon emission for
larger separations.
