The Implementation Of Phase Gate And The Generation Of Multi-dimensional Entanglement State Via Cavity QED System

Our era is information age. Information Science and Technology have been going deep into all aspects of society. With the rapid development of information science, classical information science is faced enormous challenges. Quantum information, a new subject, is a combination of quantum mechanics and information science. It is attracting more and more attention of all aspects since its potential applications and great scientific significance, which will bring about unpredictable influence for mankind. As one of the most attractive frontiers, quantum information science has become the research focus of the international academic community. Quantum information includes quantum computing and quantum communication. Quantum entanglement is the invaluable resource for quantum information and quantum technologies. Most of previous studies involve quantum entangled states based on two-dimensional quantum systems. Then it is discovered that high-dimensional entangled states has significant advantages in ensuring information security, opposing noise, and saving computing resources. In additional, the quantum phase gate is one of the essential logical gates for implementing the quantum computing. So it is important to study the physical realization of quantum entanglement state and phase gate.The cavity QED, which is one of important physical implementation systems for quantum information process, plays the significant role during the development of quantum information science. Therefore, I devoted myself into implementing phase gate and preparing high-dimensional entangled state during my graduate study.The main contents of this dissertation are as follows:1. The quantum controlled phase gate is realized and N-qubit W-like state is created based on the large-detuned interaction among three-state atoms, dual-mode cavity, and a classical pulse. In this scheme, a class of W states that can be used for perfect teleportation and superdense coding is generated by only one step. Cavity decay is largely suppressed because the cavity is only virtually excited and always in the vacuum state. The atomic spontaneous emission is strongly restrained because the excited state is not populated for a large atom-field detuning2. A scheme is presented for creating three-dimensional entangled state via adiabatic evolution in the cavity and.ber system. Our scheme has the advantages that the atomic spontaneous emission and the decay of optical.elds can be greatly reduced since atoms are all in ground states and the.elds remains in vacuum state in the ideal case. In addition, the prepared maximally three-dimensional entangled state is spread among separately cavities, which is important in view of distributed quantum computation and multi-party quantum communication. The protocol can be further extended to prepare three-dimensional multi-particle entangled state.