Figure 1:

Graphical representation of our composite system. A) Original configuration: Emitter interacting with a EM bath B through the spectral density J(ω). B) Original configuration with the EM bath B split into two independent contributions, B ₁ and B ₂, to which the emitter coupling is encoded in the spectral densities J _fit(ω) and ΔJ(ω), respectively. C) Model configuration: B ₁ is substituted by N interacting modes coupled to a spectrally flat auxiliary EM bath B _aux. The discrete modes are also coupled to the emitter, conforming a new open quantum system S.