Quantum entanglement of the coherent field interacting with the moving atom being in a mixed state

Using the negative entropy method,the quantum entanglement character of the system of the coherent optical field interacting with the moving atom is studied.The influences of the atomic initial state,the field-mode structure parameter,the average photon number of the coherent field,the detuning,and the transition photon number on the entanglement character of the system are discussed.The result shows that the value of the entanglement degree of the system appears regular evolution and entanglement sudden death phenomenon(ESD)when the atomic motion is considered.When the atomic initial state tends to pure state,the entanglement degree of the system is larger relatively.With the increase of the average photon number of the coherent field,the value of the entanglement degree of the system becomes small,but the period for the regular evolution is almost unchanged.With the increase of the transition photon number,the value of the entanglement degree of the system becomes larger,the period of the oscillation becomes shorter,meanwhile the oscillation of the system becomes faster and faster.With the detuning increasing,the entanglement becomes small.