Classical speed limit of evolution in phase space. The black solid line is the absolute value of the Bhattacharyya coefficient derivative |B˙(ϱ0,ϱt)| . The red dashed line is the Mandelstam–Tamm upper bound of speed vΓCSL reported in Ref. [45]. The blue dot-dashed line is the Margolus–Levitin upper bound of instantaneous speed v_csl in Eq. (36). The unit of time is set by ω0−1 .