Concentration And Transfer Of Atomic Entangled State Based On Cavity QED

It is undeniable that our convenient access to information is built on the basis of information science. But, The overall performance of the existing information systems is close to its theoretical limit. To meet the increasing demand for information, new principles and methods of information science must be explored. In this context, quantum information science came into being. Quantum Information, which is the combination of Quantum Mechanics and Information Science, is a new discipline. Theoretical and experimental studies have shown that Quantum Information can break the classic information technology bottleneck.Cavity quantum electrodynamics (C-QED) scheme has been considered to be one of the most promising quantum hardware design schemes. The main feature in QED scheme is that quantum information is stored in the energy states of atoms which is in the high-quality cavity, and atoms are used as quantum information storage unit. Quantum gate operations and quantum information transmission can be realized by the manipulation of optical cavity. With the progress of the experiment concerning cavity QED, it is necessary to further explore new theoretical scheme for quantum information processing. To this end, we focus on the new atomic entangled state concentration and transfer. The main research results of this thesis are follows:1. We propose a concentration scheme of the W class state via cavity QED technique. In our scheme the influences of cavity decay and atomic spontaneous emission have been considered. Furthermore, the atomic spontaneous emission has been suppressed by using non-radiative transitions in atoms with three-level structure, and the photonic qubit is used as flying qubit and atomic qubit as stationary qubit. As a straightforward extension, we will discuss the concentration scheme of N-atom W class state. 2. We present a physics scheme for transferring an unknown atomic entangled state without Bell-state measurements via cavity QED. In the transfer process the interaction between atoms and a sing-mode nonresonant cavity with the assistance of a strong classical driving field. The scheme is insensitive to both the cavity decay and the thermal field. In addition, the success probability can reach1.0in our scheme.3. We propose an efficient scheme for transfer of unknown atomic entangled states via cavity decay. In this paper, the entangled states of two atoms trapped in two corresponding cavities are teleported to another two single atoms trapped in another two corresponding cavities by detecting the photons which leak out from the cavities. In our scheme, cavity decay has been taken into consideration and plays a positive role in quantum information processing. The most distinctive advantage of our scheme is that a direct carrier of quantum information between distant atoms is not required.