Simple model for realizing coherent ergotropy in open quantum systems.

The advantage of quantum heat engines turns out to be the ability to utilize the quantum resources, such as the quantum coherence, which is, however, suppressed by the irreducible thermal dissipation of baths. Herein, we construct a two-qubit system that is coupled in different directions to the thermal bath with a single pseudomode, which can be regarded as a simple model for the establishment of the coherent contribution of ergotropy in the non-Markovian environment. It is found that the presence of coupling anisotropy gives rise to the long-standing quantum coherence that is essential for the coherent ergotropy, while with merely isotropic coupling, the incoherent contribution of ergotropy dominates. The stronger the anisotropic couplings, the greater the coherent ergotropy, and a completely coherent ergotropy can be observed in both antiferromagnetic and ferromagnetic cases. In addition, this significant ability to extract work from quantum coherence can be extended to multiple-qubit systems. Our model, therefore, provides a proof-of-principle pathway for the utilization of quantum coherence in heat engines.