Qubit thermodynamics far from equilibrium: two perspectives about the nature of heat and work in the quantum regime

Abstract: Considering an entropy-based division of energy transferred into heat and work, we develop an alternative theoretical framework for the thermodynamic analysis of two-level systems. When comparing these results with those obtained under the standard definitions of these quantities, we observe the appearance of a new term of work, which represents the energy cost of rotating the Bloch vector in presence of the external field that defines the local Hamiltonian. Additionally, we obtain explicit expressions for the temperature, the heat capacity and the internal entropy production of the system in both paradigms. In order to illustrate our findings we study, from both perspectives, matter-radiation interaction processes for two different systems.