Fig. 8: Wigner functions of the QB state.

Plot of \({{\mathcal{W}}}(x,p,t)\) (units ℏ⁻¹ = 1) as a function of x (units \({x}_{0}=\sqrt{\frac{\hslash }{2m{\omega }_{0}}}\)) and p (units \({p}_{0}=\sqrt{\frac{\hslash m{\omega }_{0}}{2}}\)). Here, darker (lighter) colours denote smaller (larger) values. (a) shows the Wigner function of the QB in its ground state right before coupling to the charger (t = 0). b represents it in correspondence of the first maxima of the efficiencies η_B and η_W. It is worth to note that the axis scales of the two figures differ by a factor of about 10. The considered parameters are ω_D = 2ω₀ (corresponding to Ω ≈ 24.5ω₀) and γ₀ = 300ω₀, T = 0.1ω₀.