Photons and electrons are the key quantum media for the quantum information processing based on solid state devices. The essential ingredients to accomplish the quantum repeater were investigated and their underlying physics were revealed. The relevant elementary processes of the quantum state transfer between a single photon and a single electron were analyzed, to clarify the conditions to be satisfied to achieve the high fidelity of the quantum state transfer. An optical method based on the Faraday rotation was proposed to carry out the Bell measurement of two electrons which is a key operation in the entanglement swapping for the quantum repeater and its feasibility was confirmed. Also investigated was the quantum dynamics in the electron-nuclei coupled spin system in quantum dots and a couple of new phenomena were predicted related to the correlations induced by the hyperfine interaction, namely, bunching and revival in the electron spin measurements. These findings will pave the way to accomplish the efficient and robust quantum repeater and nuclear spin quantum memory.
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