The Experimental Research On Quantum Correlation Of Two Light-Manupulated Atomic Ensembles

Atomic coherence is very important in quantum information、precision measurement and quantum imaging. Raman scattering and Electromagnetically induced transparency are the common methods to prepare atomic coherence. Raman scattering has been used in many ways in scientific research and industry, the frequency of Raman scattering light is related to the level structure of scattering media, more important, there will be a coherence between the levels; Raman scattering’s applications in substance tests、precision measurement quantum information、biological imaging and some technical areas are based on the manipulating of Raman scattering light and coherence. Most of the past researches were about molecules; but the coherent time of molecule is short; many applications in quantum information、precision measurement and biological imaging are based on a long coherent time; atomic ensemble has long coherent time, so it becomes one of the most common medium in these fields.Then considering the Raman scattering in atomic ensemble has momentous significance, In this process the phase correlations between different physical quantities are very important, because the efficiency of storing/retrieving quantum information、the signal-noise ratio in quantum imaging and the phase measurement in precision measurement are associated with the phase characters of light or atom. The absolute value of phase cannot be measured, the studies of phase have to involve two coherent sources, and the correlation between these two coherent sources can be obtained through interfering. On the other hand, Electromagnetically induced transparency can be used to prepare atomic coherence, and is used in some scientific research fields. We need to further study these processes, and this is conducive to controlling the light-atom interaction process. In this thesis, we do experimental researches on the phase characters of light and atomic coherence in Raman scattering, and realize higher extraction efficiency based on the atomic coherence in Electromagnetically induced transparency, as follows: First, by using spontaneous Raman scattering processes, we produce two independent Raman Stokes fields from an Rb atomic ensemble. Temporal beating is observed between the two directly generated Stokes fields in a single realization by interfering; we also measure the phase of Raman Stokes field; and the result indicate that the phase of Raman Stokes field is random. On the other hand, the intensity correlation enables us to study how the temperature effect on the dephasing process.Second, by using Raman scattering processes in87Rb atomic ensembles, we study the characters of atomic excitation, and the result indicate that the phase of atomic excitation is random, this prove that the atomic excitations from two independent Raman processes are coherent.Third, we observe both the Stokes field and the accompanying collective atomic excitation at the same time, we find that, the phase of the Stokes field and the atomic excitation are correlated; on the other hand, we realize high visibility interference based on the correlation.Fourth, we realize storage and retrieval of light based on Electromagnetically induced transparency, and demonstrate the co-propagating and counter-propagating scheme in vapor87Rb atomic cell, the experimental and theoretical results indicate that the retrieval efficiency depends on the spatial distribution of the atomic spin wave. This study may have instructive sense on the application of vapor atomic ensemble in quantum optics、quantum information and nonlinear optics.