where R l, j and P l, j are the position and momentum, respectively, of bath mode l, and ω l and c l are the frequency and coupling strength, respectively, of bath mode l that are described with the Ohmic spectral density J(ω) = ζ ωe -ω/ω 0 . The friction parameter ζ determines the overall system-bath coupling strength and the high frequency cut-off is ω 0 ≫ ω S .