Study On The Enhancement Of Three Kinds Of Quantum Resources

Because of the non-classical properties of the quantum resources,quantum information processing can break through the bottleneck of classical information technology.However,quantum resources like quantum entanglement(QE),quantum coherence(QC)and quantum Fisher information(QFI)are subject to decay,even vanishing,during the transmission process.In face of the attenuation problem of quantum resources,we suggested two theoretical schemes in this thesis to enhance the quantum resources during the transmission.Firstly,we studied the QE purification in amplitude damping channel by quantum swapping with the help of environment measurements.The results were as follows.If the initial states were any entangled odd parity states with one pair being the flipped state of the other.When we suggested |00? and |?~±? as the results of environment measurements and Bell measurement separately,the final state can be the Bell state.Otherwise,if we suggested |?~±?as the results of Bell measurement when kept the environment measurements results unchanged,we can still achieve QE purification for most of the parameters.For the situations of the initial states being identical,any entangled odd parity states and any entangled even parity states,we got the similar results.However,the QE purification effects of our schemes can't be enhanced by iteration.In our scheme,environment measurements worked as the selector for proper states and the QE purification effects were bound up with the Bell measurements.Secondly,we studied the enhancement effects of partially collapsing measurements on QC and QFI of the states transferring in the spin chain.The results were as follows.When the state parameters satisfied ??(?/2,?),single weak measurement(WM)can enhance the QC and QFI and the same optimal result can be always obtained.When the state parameters satisfied ??(0,?/2),weak measurement together with quantum measurement reversal(QMR)can enhance the QC and QFI.These two situations complemented each other.We assumed that the probabilistic nature of our scheme was the reason of the enhancement effects of QC and QFI.Besides,we discovered and proved the quadratic relationship between QC and QFI.