Cavity-Quantum Dot System In Decoherence Free Subspace

Quantum information is an interdisciplinary subject which is the combination of classical information and quantum mechanics. Quantum states as a carrier of information has classical information does not have the transmission capacity and security in quantum information. Quantum entanglement is a unique phenomenon in the quantum world, and quantum entangled state can serve as an important physical resource, have an important role in quantum information science.Quantum system cannot be a closed system because of the information exchange, quantum state inevitably interacts with the environment and induces quantum decoherence. To avoid the decoherence, the most used method is cavity quantum electrodynamics, decoherence-free subspace and quantum error correcting codes. Quantum code includes quantum error proofing code, quantum avoiding code and quantum error correcting code. The essence of decoherence-free subspace is quantum error avoiding code. Quantum dots have longer time imprisoned in cavity QED and can be accurately addressed, they can be used as the carrier of the quantum information. The qubits encoded in decoherence-free subspace, and then the entangled states are prepared in the cavity, the quantum information processing or quantum network is formed by using the photon as the transmission media to link the cavities.This dissertation consists of five chapters. In the first chapter, we introduced the research background. In the second chapter, we firstly introduced the optical cavity and its quality factor, resonator modes, resonator types, stability and delay, and then introduced the treatment method of interactions between two-level atoms in cavity and resonator mode in semi-quantum theory and full quantum theory, at last we described the basic theory of cavity quantum electrodynamics. In the third chapter, we firstly introduced the decoherence-free subspace and its existence conditions, and gave a simple example, and then lists the difficulties and solutions encountered by classical coding expansion to quantum coding, then quantum error correction code are introduced, at last we briefly discussed the decoherence-free subspace applications in quantum information processing. The fourth chapter is about our research work, we combined with cavity QED system and solid-state quantum dot system in decoherence-free subspace, to constructing parity-check gate using the input and output relations of double quan-tum dot in optical cavity, and then building quantum gate, preparing quantum entangled states and entanglement purification. The last chapter summarized the work of this paper and prospects the future of quantum information science.