Non-classicality And Quantum Entanglement Character Of Number-Phase State Interacting With Two-level Atom

In the field of quantum optics, applied some build classicality state light field, the interaction between light and matter the classical effect of system, can be more practical to reveal the quantum properties of light field. The Number-Phase light of the middle state which is made up of the Number state and the Phase state behavior of superposition, it is a structure of quantum field. To study the quantum effect of the number-phase state is very important in physics. The non-classicality and quantum entanglement character in a system which is composed of a two-level atom interacting with an intermediate Number-Phase state is studied by means of the fully quantum theory. The main content of this paper are as follows:Firstly, the time evolution of atomic population and atomic dipole squeezing, the quantum fidelity and the quantum entanglement characteristic are introduced.Secondly, the dynamical effects in a system which is composed of two-level entangled atoms interacting with an intermediate Number-Phase state are studied. The influence of the parameters of system and the degree of entanglement of two-level entangled atoms on the time evolution of atomic population and atomic dipole squeezing are analyzed. The result shows that the atomic population and atomic dipole squeezing appear different oscillation when initial state of the entangled atoms is different. The phenomena of collapse followed by periodic revivals of atomic population can be exhibited via choosing appropriate parameters of system and the degree of entanglement.Thirdly, the fidelity in a system composed of a moving two-level atom interacting with an intermediate Number-Phase state is studied. The influences of the atomic initial state, the largest number of photon, the parameter of light field, atomic motion, the parameter of field mode and the values of the transitional photon number on the fidelity of the system are analyzed. The result shows that the values of the average fidelity of system and light field decrease via increasing the largest number of photon or reducing the parameter of field. The larger atomic motion or field-mode structure parameter becomes, the greater values of the fidelity of system and light field are, and their oscillating frequencies are faster. As the transitional photon number is at different value, the evolutions for the fidelity of system and light field show several different behavior. When an atom is initially in a superposition state, the fidelity of system and field reaches its maximum, and the oscillating forms of the fidelity of system and field keep at a same manner.Finally, Entanglement characteristics in a system of a two-level atom interacting with a number-phase state field are investigated. The entanglement degrees of the system are calculated. Influences of the initial atomic state, parameters of field phase, largest-photon number, parameters of light field and transition photon number on the entanglement degree of the system are analyzed. Results show that when the initial atomic state is in superposition state, and the field phase parameter is small relatively, the entanglement degree of the system is large relatively. When the appropriate largest-photon numbers and transitional photon numbers are chosen, the smaller the field parameter is, the more obvious the entanglement phenomenon is.