The Template Help of Thesis for Master’s Degree of Shanxi University
|Keywords||atom localization Three-level system in the (?) configuration Four-level system in the double-(?) configuration electromagnetically induced transparency the collective phase the detuning|
In recent years, extensive attention has been take to the precision position measurement of an atom and acquired wide applications.As we know the atom localization is very important in the field of quantum information.Optical manipulations provide an effective method to the measurement of atom localization,it probing the center-of-mass degrees of freedom of atoms with subwavelength precision. The interest in subwavelength atom localization is largely due to its applications to many areas requiring manipulations of atomic center-of-mass degrees of freedom, such as laser cooling, Bose-Einstein condensation, and atom lithography, by the fundamentally important issues measurement of the center-of-mass wave function of moving atoms.By using the standing wave one can obtion precision positiont of an atom. We use a standing-wave field as the driving components,and a weak field as the probe components we know the Rabi frequencies of the standing-wave fields depened on the atom position so through detecting the probe components we can obtion the atom position,which play an important role to the measurement of atom.More recently,some schemes which are based on electromagnetically induced transparency (EIT) have been proposed for the atom localization of three—level atom and has meet with great achivement, Furthermore the four-level system has attracted much more consideration.For the three-level.We consider theΛconfiguration, using a standing-wave field as the driving components,and a weak field as the probe components. By analyzing the probe absorption, we find that the numbers and the widths of the localization peaks can be controlled by the Rabi frequencies of the standing-wave fields. the atom is localized in either of the two half-wavelength regions with 50% detecting probability. To four-level le atomic, we study the atom localization of a four-level system in the double-Λconfiguration. We use a strong bichromatic field (one component of which is standing-wave field) as the driving components,and a weak bichromatic field as the probe components. The theoretical analysis show that atom localization is dependent on the collective phaseφand the detuning△. In the range of the region, the detuning△influences the width and number of localization peaks. the collective phaseφinfluences the height of localization peaks.When 0≤φ≤π/2 the height of the peaks in the left half-wavelength region (-π≤kx≤0) becomes higher with the increase ofφ,whereasφ=0,there is no localization peaks in the left half-wavelength region; By comparison, whenπ/2≤φ≤πthe height Of the peaks in the right half-wavelength region (-π≤kx≤0) becomes lower with the increase ofφ, whereasφ=π,there is no localization peaks in the right half-wavelength region.