Quantum Nano-system Dynamics Based on the Steepest-Entropy-Ascent Quantum Thermodynamics

In this paper, we propose a new formulation [coherent mixed (CM) states approximation] that includes mutual interactions between subsystems of a quantum composite system within the steepest-entropy-ascent quantum thermodynamics framework. The formulation has been applied to a two-level model system that interacts with a locally dynamic phonon field. This is because the non-equilibrium dynamics of quantum nano-composite systems has been reported to show drastic changes due to its dependence on the interactions and correlations with dynamic phonons, and the importance is well realized from both science and technology viewpoints. Based on the formulation of the model system, numerical analysis of population and entropy dynamics has been performed to verify the proposed method. Consequently mutual interactions between the two subsystems that cannot be handled by the hypo-equilibrium state approximation are properly included in the dynamics by the CM state approximation to indicate an intriguing long-living quantum coherence.