Manipulation Of Thermal Flux In Quantum Systems And Study Of Microscopic Devices

Nowadays, many scientists focus on physics in quantum systems. Due to the improvement of technology and the highly demand of high-quality products, it drives us to study the quantum system dynamics much. While, considering the inevitable interaction between the small quantum system and its environment, it is very important for us to study the open quantum system involving the e?ects from the external environment. Studying some physical phenomena associated with the open quantum system, e.g. energy transport of non-equilibrium quantum systems, thermodynamics in quantum process, makes us further understand quantum systems. What’s more, lots of attention are paid to the quantum devices at micro-level. For these microscopic quantum devices constitute the basic elements of large-scale integrated devices, we would like to study the functionalities of these microscopic devices, and distinguish their performance with the macroscopic devices. In our thesis, we discuss the quantum systems from two parts, one is the thermodynamics of quantum systems, the other is the properties of quantum devices.When we discuss the thermodynamics of quantum systems, firstly, we study how to control the heat transport between the systems, and explore the possibility of highperformance of quantum energy exchange. For a spin-boson system, by adiabatically modulating the system parameters, the geometrical phase is generated during the system evolution periodically, and we can obtain the heat current induced by this geometrical phase in such systems. Secondly§the fluctuation theorems in an open quantum system and associtated thermodynamics laws are addressed. The application of generalized thermodynamics second law is presented, and the Brownian particles are chosen as an example. Later, we derive the non-Markovian quantum fluctuation theorems and Jarzynski equality by using quantum state di?usion(QSD) trajectories. Then, we study a mechanical resonator system, what we care about is to cool the mechanical resonator e?ciently. With the chirped pulse, we can cool the mechanical resonator in the microdisk-wave guide optomechanical system containing the dispersive and dissipative interactions. When we talk about the defects in the optomechanical system, we find that these defects can transfer the energy from their environment to the resonator, and the cooling performance of resonator is a?ected.We apply the periodical σzpulses to the defects, and the defects’ heating e?ect can be eliminated.The study of quantum devices steps forward to the large-scale integrated devices. We design a polarity-controllable quantum thermal diode in the coupled two-quantum-dots system at first. This diode can transfer heat in unidirectional way. Next, we discuss the mode selective excitation in molecular junctions. We can excite the certain vibrational mode of junction by applying the external voltage bias. It paves a new way to control the dynamics of intra-molecules. Finally, we bring forward a high e?ciency single photon resource with the non-linear optical cavity. This proposal will be employed in the quantum key distribution to improve the e?ciency of quantum teleportation.