Analysis Of The Mechanism Of Quantum Entanglement In A Resonant System Of Cascade Three-Level Atom And Two-Mode Field

Quantum entanglement is an important phenomenon of quantum mechanics. If two particles entangled, one particle state will instantly change accordingly when another particle change the state due to certain disturbances (such as quantum mea-surement). In recent years, quantum information and quantum communication has been rapidly development. And quantum entanglement also has been been widely and deeply studied which as the basic resource in information processing. How to prepare good stability, anti-interference ability entangled source has become the focus of researchers’ attention.What we consider is a cascade three-level atomic system. Two classical field driven atomic transitions and two mode cavity fields are coupled to the two transitions in this system. We analyze the interaction Hamiltonian of the system in the case of two mode resonances, and discuss the possibility of generating entanglement in various region. In the good cavity limit, we can obtain the entangled image of the two mode cavity field by numerical calculation. It is found that the entanglement exists almost in the entire region except for the situation of atomic populations trend to be equal. And with the decreasing of cavity loss rate, the entanglement is enhanced. In order to make the physical mechanism of entanglement more clear. We redefine a pair of squeeze transformed modes under the dressed state representation. And the entanglement of two cavity modes is analyzed by using dressed atomic states and squeezed transformed cavity modes. In the dressed-atom squeezed-transformed-mode representation, the single channel interaction is established between the dressed atom and the squeezed transformed cavity mode. Resonant interaction happened between the dressed atom and two squeezed transformed cavity modes in turn through this dissipation channel. Analyzed the produced entanglement image by using the dissipative mechanism, we found that the results of the analysis are consistent with the numerical results. This proves that the direct mechanism of generated entanglement is dissipation.