Quantum non-Markovianity, quantum coherence and extractable work in a general quantum process

Abstract: A key concept in quantum thermodynamics is extractable work, which specifies the maximum amount of work that can be extracted from a quantum system. Different quantities are used to measure extractable work, the most prevalent of which are ergotropy and the difference between the non-equilibrium and equilibrium quantum free energy. Using the former, we investigate the evolution of extractable work when an open quantum system goes through a general quantum process described by a completely-positive and trace-preserving dynamical map. We derive a fundamental equation of thermodynamics for such processes as a relation between the distinct sorts of energy change in such a way the first and second laws of thermodynamics are combined. We then identify the contributions made by the reversible and irreversible processes in this equation and demonstrate that they are respectively responsible for the heat flow and change in the extractable work during the process. Furthermore, we discuss the potential benefit of this assignment in favor of a clear explanation of the impact of quantum effects on the evolution of extractable work. Specifically, we establish this by directly connecting the extractable work with standard quantifiers of quantum non-Markovianity and quantum coherence during the process. We illustrate these results with two examples.