Entanglement Witness Construction Based On Generalized W-like States

Quantum entanglement is a special phenomenon in quantum mechanics,which provides an important physical resource for quantum information processing.How to detect and measure quantum entanglement has become an important problem.Its has prompted the discovery of many separable criteria for quantum states.For two-qubit quantum states in 2 × 2,2 × 3 systems,PPT criterion is necessary and sufficient condition.However,there is no universal criterion to distinguish entanglement from separable quantum states in the case of high dimensional and multiparties system.In recent years,many sufficient conditions for the detection of entanglement have been discovered by scholar s,one of the simple methods is entanglement witness.In the past few decades,there we re lots of new developments in the theory of entanglement witness.Usually,that is o urgoal to construct and optimize the entanglement witnesses so that they can detect m ore entangled states.We construct a series of entanglement witnesses based on generali zed W-like states in this thesis,and the main research contents are as follows.(?)We construct a k-two-parties entanglement witness to detect entanglement.For the generalized W state with noise and the generalized GHZ state mixed with generalized W state,more k-two-parties entangled states can be detected by such entanglement witnesses.(?)We discuss the properties of the constructed entanglement witnesses.The intersection of entangled states detected by the series of entanglement witnesses is empty.We give the forms of quantum states detected by the entanglement witnesses and show that a class of entangled states cannot be detected by such entanglement witnesses.