Studies On Quantum Coherence Characters Of Rydberg Atoms

Rydberg atom has abundant research significance and application values because of its special physical properties. It is one of the important research contents of attention and research in physics. The development of laser technology provides more research technology and approach for the development of Rydberg atoms. The emergence of ultracold atomic physics provides a perfect platform for the development of Rydberg atoms. Thus the study of Rydberg atoms has a great breakthrough in theory and experiment. The kinetic energy of Rydberg atom can be neglected in the field of ultracold atoms and the atom is almost stationary. Therefore, the interactions between Rydberg atoms have a main influence on dynamic behavior of atoms. In addition, dipole blockade effect, the unique property of Rydberg atom, also attracts widespread attention. Quantum logic gates and manipulation of quantum state can be realized through dipole blockade mechanism. The special properties of Rydberg atom are related to some important issues of atomic physics and quantum information, but also have significant research value and broad application prospects in plasma physics and astrophysics. On the other hand, some typical atomic coherence and quantum interference effects are the key research contents, such as electromagnetically induced transparency(EIT), coherence population trapping(CPT), and spontaneous emission enhancement and cancellation(SEEC) and so on. Recently, the research of quantum coherence is expanded to ultracold Rydberg atom field which has strong interaction. Studying quantum coherence characters of Rydberg atoms has a positive impact on the development of Rydberg atoms.In this paper, we discuss the quantum coherence phenomena in the three-level ladder Rydberg atoms based on the dipole interactions between atoms. The influence of dipole interactions between Rydberg atoms on electromagnetically induced transparency is investigated in detail. Besides, the influence of dipole interactions on optical bistability of Rydberg atom is discussed. The main context is as follows:(1) We study the EIT linear and nonlinear optical properties of Rydberg atomic medium. A strong control field and a weak probe field have interactions with three-level ladder Rydberg atoms. Interative method is used to calculate the first-order linear solution and third-order nonlinear solution of density matrix elements. In this way we study the absorption and dispersion in different interactions. The results show that a typical phenomenon of electromagnetically induced transparency is apparent if we don’t consider the dipole interactions. When dipole-dipole interactions are considered, the linear and high ordernonlinear optical properties change, showing some regularity due to the interactions of Rydberg atoms.(2) We demonstrate the optical bistability behavior of three-level Rydberg atoms. A probe field and a control field have interactions with three-level Rydberg atoms and N three-level atoms that homogeneously broaden are placed in a unidirectional ring cavity. The optical bistability behaviors are discussed under the condition of considering the dipole interactions between atoms. The results show that the dipole interaction between Rydberg atoms has a certain impact on optical bistability behavior. Specifically, the bistable threshold increases along with the increase of the dipole interaction between Rydberg atoms, and the atomic absorption of light field enhances. Therefore, the optical bistability behavior can be controlled through adjusting the intensity of the dipole interaction between Rydberg atoms.In short, we study the optical properties of electromagnetically induced transparency and optical bistability based on dipole-dipole interactions between Rydberg atoms through interactions between external field and Rydberg atom ensemble. Our research can not only help to promote the understanding of quantum coherence effects, but also has a positive effect on the study of Rydberg atomic features and provides the theoretical help for quantum coherence properties of Rydberg state.