Transmission Of Polarized Photons In Atmosphere And Interaction Between Single Photons And Cavity-quantum Dots

In recent years, much attention has been paid to quantum information based on the principles of quantum mechanics and information science. As an important branch of quantum information, quantum communication, with quantum states as information carriers, overcomes the traditional cryptography security risk, and is "absolutely safe" in theory. Because the free space quantum key distribution plays a significant role in building the global quantum secure communication network by satellites in future, it is necessary to study the effects of the atmospheric channel on photons carrying the key information while propagating in free space. In addition, in order to build a large-scale quantum network, various quantum modules need to be connected via quantum interface to increase their scalability. Cavity-quantum dot is an effective quantum interface. Solid qubits are suitable for storage bits, while photons are used as flying qubits. So the study of interaction between stationary solid qubits and flying photons is one of the important researches for quantum communication.Based on the above mentioned reasons, two researches are mainly carried out in this thesis:1) Research on scattering propagation properties of polarized photons in free space communication.2) Research on the dynamic evolution of interaction between the single photons and cavity-quantum dots.In the first research, based on Mie scattering theory and the vector radiative transfer theory, we carry out the simulation of the transmission of polarized photons in atmosphere mainly adopting Monte Carlo method. Firstly, we study a multiple scattering vector transmission model of polarized photons based on the single scattering model. Then we take atmosphere as a multilayer medium, and propose the concept "virtual particles" to establish the scattering model of polarized photons in the multilayered atmosphere. By programming we get the effects of the single scattering on polarization degree of photons, scattering phase function, the coordinate distribution of the scattered photons, tomography of polarized photon scattering Mueller matrix and the changes of the Stokes vectors of polarized photons propagating in different visibility and at different height. The results show that these models can explicitly reveal the changes and their rules of photons polarization in all kinds of atmospheric propagating processes.In the second research, we study the system composed of quantum dots doped with single electrons, solid optical micro-cavity and fiber. Based on the cavity-quantum dot system model, we mathematically derive the dynamic evolution of interaction between single photons and cavity-quantum dots. The mutual transformation between the stationary qubits and flying photon qubits can be realized by numerical simulation, and the entanglement between the photons and atoms in the quantum dots can be realized by changing the parameters such as laser pulse time.