Entangled quantum heat engine based on two-qubit Heisenberg XY model

Based on a two-qubit isotropic Heisenberg XY model under a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE). The expressions for the heat transferred, the work, and the efficiency are derived. Moreover, the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically. Several interesting features of the variations of the heat transferred, the work, and the efficiency with the concurrences of the thermal entanglement of two different thermal equilibrium states in zero and nonzero magnetic fields are obtained.