Fig. 9
From: Quantum engine efficiency bound beyond the second law of thermodynamics
Different evolution paths. a The evolution of an initial state ρ0 in a non-thermal bath according to the Liouvillian \({\cal L}_{\it U}\) (solid path) is unitarily equivalent to the evolution of a state \(\tilde \rho _0\) in a thermal bath according to the Liouvillian \({\cal L}_{{\mathrm{th}}}\) (dashed path). b The steady state reached by the relaxation of a non-passive state ρ0 in a thermal bath (solid path) may also be reached by an alternative (dashed) path wherein the initial ergotropy is first removed in a unitary process
