Quantum Information Processing Based On Bad Cavities

Quantum information science is an interdisciplinary which combines quantum mechanics, computer science and information science. It can be used to complete tasks which can not be realized with classical information science, and its potential applications lead to both theoretical and experimental studies in recent decades. Nowadays, quantum information processing may be implemented in many different physical systems such as linear quantum optics, nuclear magnetic resonance, ion trap, quantum dot, nanomechanical resonator, circuit quantum electrodynamics and cavity quantum electrodynamics. Cavity quantum electrodynamics system is widely regarded as one of the most promising platforms, as it has been investi-gated for decades and is closely related to experimental technology in quantum optics. Due to the fact that preparation of high-quality optical cavity is difficult with present experimental technology, and integration of cavity quantum electro-dynamics with high-quality optical cavity is a great challenge, in this thesis, we mainly investigate quantum information processing based on bad cavities theoret-ically.In chapter1, we introduce the relevant knowledge about quantum information processing within cavity quantum electrodynamics, then present the motivation and arrangement of our thesis.In chapter2, we briefly introduce relevant background of cavity quantum electrodynamics. We first discuss Jaynes-Cummings model and input-output the-ory of cavity, then introduce physical implementation systems for cavity quantum electrodynamics, and give some basic concepts and relevant parameters lastly.In chapter3, we discuss quantum logic gates based on bad cavities. Firstly, we recall photonic input-output process and photonic Faraday rotation, and then pro-pose quantum parity gate, atom-photon controlled-not gate and controlled phase gate, respectively. We also discuss their experimental feasibility and error analysis.In chapter4, we discuss quantum entanglement concentration and purification based on bad cavities. For quantum entanglement concentration, we present two different schemes:one is entanglement swapping, the other is optimal entangle-ment concentration based on quantum logic gate and single-qubit measurements. Bennifitting from photonic input-output process based on bad cavities, we can con-centrate both atomic and photonic entanglement. Furthermore, we also propose atomic entanglement purification with weak coherent light. Finally, we discuss their experimental feasibility and error analysis.In chapter5, we discuss quantum teleportation based on bad cavities. Firstly, we present teleportation protocol for multiqubit quantum state, and show that it consumes less quantum entanglement, qubits and classical information than previ-ous ones. Based on photonic input-output process in the bad cavity, we propose to teleport both atomic and photonic states, and discuss their experimental feasibility and error analysis.In chapter6, the summary and outlook are given.