Quantum Entanglement In The Xy And Jc Model And The Light Field Of Quantum Effects

When Einstein,et al put EPR Paradox forward in 1935,physical scientists had paid attention to the specialities of quantum states about entanglement.With the development of quantum information theory and advance of quantum computer,quantum entanglement has been applied to quantum computation,quantum information and quantum communication as an important resource.Entanglement can realize quantum cryptography,quantum teleportation and quantum long communication,et al,which are difficult to be realized by classical methods.Entanglement has the properties of inartificial secrecy,super high speed and super capacity.The deep study about entanglement will affect not only quantum information basic theory but also the future potential practical application.Solid state systems,due to the easy integration,are the promising candidates for realizing quantum computation.Vast literatures show that spin chain is one of the systems used for quantum computation and quantum communication.It is helpful to explain and find new phenomena to study the many-body systems,such as spin chain.Quantum entanglement is the phenomenon which the classical theory is unable to explain, similarly non-classical effects,some papers have proved that the degree of entanglement always follows one of squeezing and antibunching and the entanglement is increased along with the increase of one of nonclassical effects.In addition,input state owning nonclassical properties is a necessary condition to generate quantum entanglement state.In this paper,we mainly investigate that thermal entanglement in a two-qubit Heisenberg XY model with external magnetic fields and quantum statistical properties of entangled light fields in nondegenerate k-photon J-C model.The main results of this thesis are as follow:1.To investigate the effects of thermal entanglement in the presence of uniform magnetic field and inhomogeneous field together in Heisenberg XY model,we exert two controllable magnetic fields(B+b)and(B-b)on coupled two-qubit system.We fred that the entanglement between the two qubits exhibits a platform and appears mutation in low temperature and under the uniform magnetic field.By controlling the inhomogeneous magnetic field b and selecting suitable material we can get the most favorable entanglement and enhance the critical temperature Tc of dead entanglement greatly.We also find that the entanglement switch can be realized in broader region of temperature by modulating the uniform fields B.2.Considering two-mode entangled coherent light fields,one mode of the fields is poured into the cavity with a two-level atom and interacts with it by k photons non-resonantly.During the course of Cavity-QED evolution of the total system,we have a selective measurement to the atom.Through operating the evolution time and changing detuning,we can control the effects such as anti-bunching and squeezing,and we can also change the level of non-classical property in this way by using the technique for Cavity-QED with k photons and non-resonance and the entangled correlation between the coherent light fields.We have more effectively implemented the target that control or change the non-classical properties of coherent light fields remotely.