Protection Of Entangled State Based On Environment-assisted Measurements And Weak Measuremnets

Quantum information science is an interdiscipline that formed by the combi-nation of quantum mechanics and classical information science,as the core physical resource,quantum entanglement has important applications in quantum information processing.However,in practical processes of information transmission,processing and storage,the inevitable interaction between quantum system and their environ-ments would lead to quantum decoherence,even to sudden death in some cases.Therefore,protection of the quantum state from noise is a critical problem.In the past decades,scientists have proposed many schemes for entangled state protection,but these schemes always have some defects.In this paper,we propose a scheme for protecting quantum states and quantum information processing agreement based on environment-assisted measurement and weak measurement.The main content is as follows:(1)We propose a scheme for protecting and improving the fidelity of quantum telecloning over the amplitude damping(AD)channels.By using the environment-assisted measurements and weak measurement reversals(WMR),the entanglement of quantum channel between three separated participants can be recovered proba-bilistically.Particularly,when the strength of WMRs is equal to the damping rate of the AD channels,the fidelity of the telecloning can be restored to the maximum value with a certain successful probability.(2)we propose a scheme to protect the tripartite Greenberger-Horne-Zeilinger(GHZ)entanglement state subjected to the generalized amplitude damping(GAD)channel based on the quantum technique of weak measurement(WM)and weak measurement reversal(WMR).By optimizing the strengthes of WM and WMR,the decoherence caused by the channel can be effectively suppressed.The results show that after performing the optimal pre-and post-channel weak measurement,the negativity of the GHZ state can be effectively improved with a certain probability,and the phenomenon of sudden death can be delayed to a certain degree.