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The study of thermodynamics of small-scale systems or quantum thermodynamics has been recently receiving a lot of attention from quantum scientists in the field of quantum information. The main purpose of this thesis is to review the effects of quantum phenomena such as correlations, on the laws of thermodynamics and specifically on the efficiency of quantum heat engines. We first review some of the most important topics of classical thermodynamics such as the laws of thermodynamics, thermodynamic potentials and heat engines. The trade-off between power and efficiency for classical heat engines is investigated. It is shown that, this is impossible to have a heat engine performing with the... 

In this dissertation, we propose and analytically investigate a scheme for effective three-dimensional cooling of a nanoparticle optically trapped in a Fabry-Perot cavity using multiple cavity modes. By employing active feedback cooling using amplitude modulation of cavity modes, our approach allows to access the UHV regime without the need for any additional means like an external tweezer or a radio-frequency trapping approach. For a set of feasible experimental parameters, we demonstrate that the cooling rates achievable are sufficient to overcompensate recoil heating. Therefore the approach is suited to trap a particle for indefinite times at UHV pressures, where air damping cannot... 

Investigation of the consistency between physical theories has always resulted in the advancement of physics. Meanwhile, study of the consistency between quantum mechanics and thermodynamics has led to the development of a branch in theoretical physics called quantum thermodynamics. In addition to the consistency problem,employing other features of quantum mechanics such as coherency and entanglement, to enhance thermodynamic processes is another ongoing subject of research. In order to study the thermodynamics of quantum systems, we use the first law of thermodynamics to present a derivation of quantum potential. Quantum potential is a term in the equations of motion of a quantum system of...