外加磁场对简并二能级原子系统相干特性的影响

在铯原子简并二能级系统中6S_1/2F=4—6P_3/2 F'=5 的循环跃迁上获得了电磁感应吸收(EIA)峰，并研究了轴向均匀磁场对二能级系统相干效应的影响，即存在轴向均匀磁场时，观测到在铯原子6S_1/2F=4—6P_3/2F'=5 跃迁频率处EIA和电磁诱导透明(EIT)的混合结构，在合适的实验条件下，其结果与Ye等(2002)的理论分析相一致. 关键词： 电磁感应吸收(EIA) 铯原子 简并二能级系统     

四能级原子系统中非线性电磁感应吸收的理论研究

在n型四能级原子系统中,研究了电磁感应吸收的非线性理论.结果表明:探测光的拉比频率和衰减分配系数A影响非线性吸收,进而影响介质吸收.当探测光光强较弱时,介质吸收和线性吸收一致,均表现为电磁感应吸收特征;当探测光光强增大时,介质吸收和线性吸收不再一致,介质吸收曲线将会呈现出烧孔现象;当探测光光强增大到控制光(或信号光)光强时,介质吸收表现出很大的增益现象.同时,非线性吸收受到衰减分配系数A的影响,即使在探测场很弱的条件下,随着A值的减小,介质吸收由电磁感应吸收现象表 关键词： 电磁感应吸收 非线性吸收 增益现象 n型四能级原子系统     

四能级原子系统中电磁感应吸收的相位控制

在以三个电偶极跃迁构成简并N型四能级系统中,利用密度矩阵方程计算了介质对探测场的吸收,研究了激光场拉比相位对吸收的影响.结果表明:介质对探测场的吸收和放大取决于控制场和信号场的拉比相位,且吸收和放大随控制场、信号场的拉比相位改变而作周期性变化,周期为2π;而探测场的拉比相位变化对吸收没有影响.同时,控制场、信号场拉比相位对吸收的影响是相同的,而且拉比相位主要影响原子相干,对原子布居影响不大.     

消除简并双光子过程中二能级原子的消相干性

研究了置于外部环境(热库)中的二能级原子在外加驱动场时原子的消相干问题.得到简并双光子过程中原子约化密度算符非对角元.在二能级原子的消相干被消除的情况下,讨论外加驱动场的特性. 关键词： 简并双光子过程 二能级原子 消相干性     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

开放简并二能级原子系统F_g=2F_e=1跃迁中的量子相干效应

文章分析了满足Fg=2Fe=1跃迁的开放简并二能级原子系统在磁场作用下的量子相干效应。该模型中,驱动场的偏振方向平行于磁场方向且与探针光偏振方向相互垂直。由于驱动场和塞曼分裂对原子的耦合作用,在不同驱动场拉比频率作用下将会分别出现电磁诱导透明(EIT)和电磁诱导吸收(EIA)效应,同时伴随相应的正常色散和反常色散。通过控制驱动场强度可以有效控制系统的量子相干效应,同时实现光速调控。     

原子与耦合腔相互作用系统中的纠缠特性

本文研究将两个二能级原子分别注入耦合腔A和B中,并且原子与腔场发生共振相互作用的情况.采用Negativity熵度量两子系统间的纠缠,利用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:随腔场间耦合的增强,两原子间的纠缠增强,而原子与腔场间和两腔场间的纠缠减弱. 关键词： 量子光学 二能级原子 耦合腔 量子纠缠     

铯原子蒸气薄池中的透射光谱

对单光束通过蒸气薄池中的铯原子6S1/2→6P3/2跃迁的透射光谱进行了实验研究,其透射光谱呈现出亚多谱勒特性。利用频率调制技术提高信号的灵敏度,同时研究了激光强度对信号的影响。     

Observation of four-wave mixing in caesium atoms using a noncycling transition

In this paper the generation of four-wave mixing (FWM) signal using a noncycling transition of caesium atoms is investigated when the pumping laser is locked to the transition $6{\rm S}_{1/2}F=4\to6{\rm P}_{3/2}F'=4$, and meanwhile the probe frequency is scanned across the $6{\rm S}_{1/2}F=4 \to6{\rm P}_{3/2}$ transition. The efficiency of the four-wave mixing signal as a function of the intensity of the pumping beams and the detuning of the pumping beams is also studied. In order to increase the detection efficiency, a repumping laser which is resonant with $6{\rm S}_{1/2} F=3\to 6{\rm P}_{3/2}F'=4$ transition is used. A theoretical model is also introduced, and the theoretical results are in qualitative agreement with experimental ones.     

The breaking point between fast- and slow-light in adegenerate two-level atomic system

This paper investigates the breaking point between fast- and slow-light in a degenerate two-level atomic system, where fast-light can be converted to slow-light arbitrarily on a single transition line by adjusting the strength of the pumping field. An equivalent incoherent pumping rate is introduced in this simplified theoretical model which exploits the dependence of this feature. The experimental observation is presented as evidence of the breaking point where the injected power is about 0.08~{\rm mW}.     

Electromagnetically—induced transparency in a multi—V—type system in cesium atomic vapour

Electromagnetically-induced transparency is observed in a three-level multi-V-type system in cesium vapour at room temperature.The absorption property is measured and the hyperfine structures of atomic states can be datermined.The results of the experiment agree with the theoretical analysis.     

Quantum interference effects in a multidriven transition Fg=3←→Fe=2

We have theoretically and experimentally studied the quantum coherence effects of a degenerate transition Fg =3←→Fe=2 system interacting with a weak linearly polarized （with σ＋ components） probe light and a strong linearly polarized （with σ＋ components） coupling field. Due to the competition between the drive Rabi frequency and the Zeeman splitting, electromagnetically induced transparency （EIT） and electromagnetically induced absorption （EIA） are present at the different values of applied magnetic field in the case where the Zeeman splitting of excited state Δe is larger than the Zeeman splitting of ground state Δg （i.e.Δe 〉 Δg）.     

Influence of selective atomic measurement on the entanglement properties of a two-atom outside cavity

Considering three two-level atoms initially in the W or Greenberger--Horne--Zeilinger (GHZ) state, one of the three atoms is put into an initially coherent light cavity and made to resonantly interact with the cavity. The two-atom entanglement evolution outside the cavity is investigated. The influences of state-selective measurement of the atom inside the cavity and strength of the light field on the two-atom entanglement evolution outside the cavity are discussed. The results obtained from the numerical method show that the two-atom entanglement outside the cavity is strengthened through state-selective measurement of the atom inside the cavity. In addition, the strength of the light field also influences the two-atom entanglement properties.     

选择原子测量对原子与光场纠缠特性的影响

考虑将初始处于纠缠态的一个原子注入处于Fock态的单模腔中,并且原子与光场发生共振相互作用的情况,采用Negativity熵来描述两子系统间的纠缠,运用数值计算方法研究了腔内原子与光场间的纠缠特性.通过是否进行原子态选择性测量情况下,对腔内原子与光场间的纠缠特性的比较,讨论了腔外原子的测量对纠缠特性的影响.研究结果表明...     

Structural properties of undercooled liquid sodium and caesium

Extensive theoretical results for the temperature dependence of the static and dynamical structure of undercooled alkali metals using Na and Cs as examples are presented. The static structural properties are obtained from the HMSA integral equations using pair potentials derived from an accurate non-local pscudopotential. The dynamical properties obtained from viscoelastic theory are compared with experiments and the results of memory function formalism. The study indicates that collective density excitations are more dominant in the undercooled region than at their melting points, and that the dynamical properties of Na and Cs exhibit subtle differences in their gross features.     

Absorption spectroscopy of cold caesium atoms confined in a magneto-optical trap

Absorption spectra of cold caesium atoms confined in a magneto-optical trap are measured around D_2 line at 852nm with a weak probe beam. Absorption reduction dip due to electromagnetically induced transparency (EIT) effect induced by the cooling/trapping field in a V-type three-level system and a gain peak near the cycling transition are clearly observed. Several mechanisms mixed with EIT effect in a normal V-type three-level system are briefly discussed. A simple theoretical analysis based on a dressed-state model is presented for interpretation of the absorption spectra.