Bekele, Mulugeta (PhD)Chegeno, Warga2018-07-092023-11-092018-07-092023-11-092011-11http://10.90.10.223:4000/handle/123456789/7219We study a quantum heat engine with a working substance as a two level single spin-1/2 system immersed in a magnetic eld region. Work is produced when the spin-1/2 system is being carried from high magnetic eld region to a low magnetic eld region. Heat is transfered when the occupation probabilities of the spin-1/2 system is changed while the energy level remains the same due to constant magnetic eld. We have found that the e ciency of the engine at quasi-static limit is equal to the Carnot e ciency. We have also found that the e ciency at maximum power of our model heat engine is equal to that of the Curzon-Ahlborn e ciencyenQuantum Heat EngineThesis