| In the atom-field interactions, the study of entanglement between different quan-tum systems and the properties of fields and atoms are two interesting subjects ob-tained continued attention. Quantum entanglement is the most valuable resource in quantum information, it have been proved that it is possible to achieve quan-tum communication with the development of quantum informatics. How to prepare stable entanglement experimentally, great concerns and effort have been paid to it. Otherwise, the spin-squeezing is also a carrier of quantum computing and quantum information. In this paper, we investigate the entanglement between atom ensembles and the spin-squeezing based on the atom-field interaction quantum theory.First, considering one three-level A ensembles in a two-mode optical cavity, research the spin-squeezing of the ensembles. By using the master equation of atom-field system, we could get the motion equations for atomic and field operators. In order to convert the operator equations to c-number Langevin equations, we have to define a certain ordering of operators correspond to the c-number equations. Lin-earization of the Langevin equations, then calculate the quantum fluctuations of two spin components, and discussed the spin squeezing properties.Second, thinking about two three-level A ensembles in a two-mode optical cavity, study the characteristic of the entanglement between two ensembles. Using the same method to get linearized c-number Langevin equations, we obtain the quantum cor-relation spectrum, and analyze physical mechanism of entanglement is nonlinearities. |
