Entanglement And Entanglement Swapping Among Multipartite Pure-state System

A combination of quantum mechanics and information science yields a new subject: quantum information science. A notable feature of this subject is that the carriers of information are quantum states. Quantum entanglement is one of the most important subject, and also, the strangest part of quantum information. In quantum information, the processing of information depends on quantum state and its evolution, while quantum entangled states certainly is the most important kind among all kinds of quantum states.We present a measure for generating entangled state of atom-cavity field, which is prepared based on the Jaynes — Cummings of atom-cavity field interaction. Through changing the interaction time, the degree of entanglement of the atom-cavity field has periodic change. It is shown that when the detuning is equal to Rabi frequency, the quantum entanglement state will stay in the maximally entangled state for a long time. This paper considers the case that one of the two entangled identical two-level atoms interacts with a single-mode field among three-body entanglement. The results show that in initialed the more the degree of entanglement of the two entangled atoms have, the more oscillation of the entanglement measure will have, and the more times of the maximally entanglement measure will obtain. Meanwhile, it is found that entanglement measure will be reduced when atomic coupling coefficient is larger than coupling coefficient between field and atom. The wave function of the system is derived by using a ∧ type three-level atom or a V type three-level atom interacting resonantly with two-mode field in pure number state. Through changing the interaction time, we can find that this system will generate entangled GHZ state in appropriate coupling coefficients, and the coupling coefficients and the time of generating entangled GHZ state will change with the variation of system state. This feasible scheme is proposed to generate entangled GHZ state. It can enlighten us in some experiments, such as quantum information storage and entanglement preparation, and provide special examples to deeply research in quantum entanglement essence. The further study to quantum entanglement will have profound influence on both basic theory and potential application.In this paper, we present a new scheme obtaining entanglement swapping through Tavis Cummings model. We consider three two-level atoms (1, 2, and 3)initially in the W entanglement stale, Then two atoms 2 and 3 are injected into single mode cavity field to make interaction, while atom 1 is far from the cavity field. The entanglement swapping can be realized periodically between atom 1 and the cavity field by carrying out measurements on atom 1.