Research And Application On Quantum Entanglement And Quantum Steering

Quantum entanglement,quantum steering and Bell nonlocality are three hierarchies of quantum correlation,and they are three fundamental problems of quantum mechanics.Quantum entanglement is a fundamental resource for quantum information processes,such as quantum communication,quantum computation and quantum simulation,etc.It can be detected by entanglement criterion or tomography measurement.For entanglement criterion,there are realignment criterion,entanglement witness and positive partial transposition criterion,etc.Quantum steering is a quantum correlation which higher than simple quantum entanglement and lower than Bell nonlocality,and it can be detected by steering inequality,such as linear and nonlinear steering inequalities.Besides,for nonlinear steering inequalities,there are all-versus-nothing steering inequality,steering inequality from uncertainty principle,etc.In this thesis,we first introduce the research background,significance and characteristics of quantum entanglement and quantum steering,and then describe the basic type and development for implementing quantum entangled source experimentally.We introduce our scheme of implementing quantum entangled source after introducing some basic knowledge of quantum entangled source.We use “sandwich-like” ?-barium borate(BBO)crystal to generate biphoton state source,e.g.the maximally entangled states,whose state fidelity can reach up to 99.3%.Finally,we use a quantum decoherence channel to control entangled states,and prepare some common quantum states,i.e.the Werner states.In this thesis,we also consider verifying a new geometric bell-like steering inequality recently proposed experimentally.Firstly,we carry out tomography measurement on the prepared Werner states in 36 sets of bases,and get corresponding experimental data.When taken experimental errors into account,the experimental values fit well with those theoretical values.The biggest advantage of this geometric bell-like steering inequality lies in that it does not need to carry out optimal measurements on certain bases,but only needs to construct out the density matrix of arbitrary two-qubit state.