The Discrimination Among The Multi-qubit Entanglement States Based On The Cavity Input-output Process

Quantum information is a rapid emerging discipline which has become the research object of many researchers in recent years.Quantum entanglement which lies in the heart of the quantum information science is extremely important physical resources in the realization of quantum computation and quantum communication tasks.It is well known that quantum entanglement states,such as Bell state,GHZ state,W state,Cluster state and so on,are the basis of quantum dense coding and quantum teleportation.So to discriminate all bases of quantum entanglement state is also very important in the process of quantum information processing.So far,there has been a lot of scientists put forward different scheme at home and abroad to discriminate all bases of Bell state and GHZ state.Compared with the Bell state and GHZ state,the Cluster states and |x>state are notable for their large capacity of information,and they are very important physical resources in the process of quantum information processing,therefore to discriminate all bases of the Cluster states and |x>state is particularly necessary.This theme mainly studies how to discriminate all of the orthogonal basis of the four-photon,five-photon cluster state and the four-photon,four-atom |x>state,respectively.In this theme,based on the cavity input-output process,we design the parity and phase discrimination devices via making use of some simple linear optical el-ements,photonic circulators and controlled phase gates.And the fidelity of some devices are also calculated.Then we construct the four-photon,five-photon cluster state discrimination devices and the four-photon,four-atom |x>state discrimination devices by combining these kinds of discrimination devices.These multi-particle en-tangled state discrimination devices can discriminate sixteen orthogonal bases of the four-photon Cluster state,thirty-two orthogonal bases of the five-photon Cluster s-tate,sixteen orthogonal bases of the four-photon and four-atom |x>state completely and nondestructively,respectively.Furthermore,the investigations of the fidelities show that our schemes are feasible under the current experimental technology.