Efficiency Enhancement up to Unity in a Generalized Quantum Otto Engine: Comparative Analysis with Conventional Quantum Otto Engine Utilizing a Two-Qubit Heisenberg XXZ Chain

Abstract: This study presents a comparative analysis of three quantum thermal engines utilizing a two-qubit Heisenberg XXZ chain as the working substance. A novel generalized quantum Otto cycle (GQOC) is introduced, featuring two distinct coupling configurations to thermal reservoirs. The GQOC exhibits the potential for 100\% efficiency, surpassing the efficiency of the conventional quantum Otto cycle. Essential conditions for positive work extraction and achieving maximum unity efficiency are derived. An experimental implementation using Quantum Electrodynamic circuits and Transmon qudit is proposed. This work contributes to the advancement of quantum heat engines, highlighting the benefits of non-equilibrium processes and asymmetric coupling for enhanced work extraction and efficiency.