Coherent control of dressed images of four-wave mixing

In two-level as well as V-type three-level atomic systems, we study probe transmission, four-wave mixing (FWM) and fluorescence signals with dressing effect experimentally and theoretically. We find both the hyperfine structure (at the same energy level) and the transition dipole moment (at different energy levels) can affect the dressing effect. We also experimentally investigate that angle-control dynamics in the nonlinear propagation of the images of the probe and generated FWM in two-level atomic systems, and find that the focusing and defocusing of probe beam and FWM signals can be greatly affected by the angles between dressing fields.     

Spatial Splitting and Intensity Suppression of Four-Wave Mixing in V-Type Three-Level Atomic System

We illustrate our experimental observation of coexisting the controllable spatial splitting and intensity suppression of four-wave mixing （FWM） beam in a V-type three-level atomic system. The peak number and separation distance of the FWM beam are controlled by the intensities and frequencies of the laser beams, as well as atomic density.     

Enhancement and suppression of spatial splitting four-wave mixing in atomic medium

We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing (FWM) process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM (DWFM) beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing.     

光场与N型四能级原子相互作用系统中原子布居的时间演化特性

精确求解了单模光场与N型四能级原子相互作用系统的波函数,并采用数 值计算方法,分析了原子布居的时间演化特性.N型四能级原子相当于具有双层精细结构的二能 级原子,在一定的条件下四能级系统可退化为V型或Λ型三能级系统或简单二能级系统.计 算结果表明,四能级系统原子粒子数布居的时间演化不具有周期性.     

A scheme for the generation of two-mode atomic laser

The quantum dynamic behavior of the system composed of V-type three-level atomic Bose-Einstein con-densate (BEC) interacting with two-mode coherent light field has been studied. The results show that the atoms of V-type three-level atomic BEC, which are excited to higher-level states under the action of light field, still keep their properties of coherent states. It demonstrates theoretically that two-mode atomic laser may be prepared by V-type three-level atomic BEC.     

Enhanced cooling of a V-type three-level atom in an optical cavity

We have studied theoretically and numerically the enhanced cooling of a V-type three-level atom in a high-finesse optical cavity and shown that the cooling rate can be increased by one order of magnitude over that of a two-level atom, and the momentum amplitude tends to a stationary state much smaller than that of a two-level atom. We have further shown that the cooling rate can be significantly improved by using feedback and a time-dependent pump.     

原子玻色-爱因斯坦凝聚体对V型三能级原子激光压缩性质的影响

利用格子液体方法对V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统的哈密顿量进行分析,发现文献中对原子间相互作用部分的处理有不合理之处,从而对该哈密顿量作出了改进并研究了V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统中原子激光的两个正交分量的压缩性质.研究表明:V型三能级原子玻色-爱因斯坦凝聚体中光场-原子相互作用强度对原子激光的两正交分量的涨落有明显的影响. 关键词： 玻色-爱因斯坦凝聚 V型三能级原子 压缩相干态 压缩原子激光     

Observations of Autler-Townes spatial splitting of four-wave mixing image

We report the self- and external-dressed Autler-Townes (A-T) splittings of the images of the generated four-wave mixing signal (FWM) and electromagnetically induced transparency (EIT) of probe images in cascade three-level atomic system. Such spatial properties of probe and FWM signals are induced by the enhanced cross-Kerr nonlinearity. We demonstrate the controlled electromagnetically induced spatial dispersion (EISD), splitting and focusing of probe and FWM signals images by adjusting self- and external-dressing fields. Studies on such controllable A-T spatial splitting and spatial EIT effect can be very useful in applications of spatial signal processing and optical communication.     

利用极化拍频光谱术研究光子回波

利用相位共轭极化拍频光谱术对Ｖ型三能级系统中的光子回波进行了研究,当抽运光束为宽带线宽且相对时间延迟〉０时,单光子四波混频对应于三脉冲受激光子回波。抽运光束为宽带线宽且相对时间延心〈０的情形与抽运光束为窄带线宽的情形类似,这种技术在测量激发态之间的能级分裂时,可得到消除多谱勒增宽的测量精度。     

Teleporting N-qubit unknown atomic state by utilizing the V-type three-level atom

Realizing the teleportation of quantum state, especially the teleportation of N-qubit quantum state, is of great importance in quantum information. In this paper, Raman-interaction of the V-type degenerate three-level atom and single-mode cavity field is studied by utilizing complete quantum theory. Then a new scheme for teleporting N-qubit unknown atomic state via Raman-interaction of the V-type degenerate three-level atom with a single-mode cavity field is proposed, which is based upon the complete quantu...     

Large index of refraction without absorption via decay-induced coherence in a three-level V system

We study the effects of quantum interference from spontaneous emission on the dispersion-absorption properties in a three-level V-type atomic system with two near-degenerate excited levels. We found that due to the quantum interference between two spontaneous decay channels, large index of refraction without absorption always can be obtained just by choosing proper values of the relative phase between the two applied fields.Received: 27 February 2004, Published online: 26 May 2004PACS: 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption - 42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift     

Optical selectivity in optically dense media driven by optimized Gaussian-type ultrashort pulse pairs

We theoretically demonstrate that selective resonant excitation can be achieved in a dense collection of V-type three-level atoms by optimizing the pulse delay and peak intensity ratio of an applied phase-tailored ultrashort pulse pair. Near-dipole-dipole interaction plays an important role in the quantum control of selective excitations since it brings about an intrinsic frequency shift in the atomic resonance, which builds up various excitation pathways. As a consequence, we can control the quantum interference between various pathways by shaping the excitation pulse pair to steer the atomic excitation selectively toward a desired quantum state.     

原子间相互作用对V型三能级原子激光压缩性质的影响

研究了V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统中原子激光的两个正交分量的压缩性质,并与三型三能级原子玻色-爱因斯坦凝聚体和双摸压缩相干态相互作用系中原子激光的压缩作了比较.结果表明:压缩相干态光场的初始压缩因子和凝聚体中原子间的相互作用强度对原子激光的两个正交分量的压缩有明显的影响,随光场压缩因子增大原子激光的压缩深度增加,而随原子间相互作用变强,对原子激光的正交分量的压缩的影响变浅.     

Teleporting <Emphasis Type="Italic">N</Emphasis>-qubit unknown atomic state by utilizing the V-type three-level atom

Realizing the teleportation of quantum state, especially the teleportation of N-qubit quantum state, is of great importance in quantum information. In this paper, Raman-interaction of the V-type degenerate three-level atom and single-mode cavity field is studied by utilizing complete quantum theory. Then a new scheme for teleporting N-qubit unknown atomic state via Raman-interaction of the V-type degenerate three-level atom with a single-mode cavity field is proposed, which is based upon the complete quantum theory mentioned above.     

V型三能级原子双模光场系统中光场压缩性质

本文利用格子液体方法对文献中给出的V型三能级原子玻色-爱因斯坦凝聚体与双模压缩相干态光场相互作用系统的哈密顿量进行分析,发现文献中对原子间相互作用部分的处理有不合理之处,从而对该哈密顿量作出了改进并研究了V型三能级原子双模光场系统中光场压缩性质.结果表明:光场两正交分量交替呈现周期性压缩现象,其压缩深度与光场初始压缩因子密切相关,而压缩时间与双模光场的频率有关. 关键词： 玻色-爱因斯坦凝聚 V型三能级原子 压缩相干态 双模压缩态光场     

Observation of linewidth narrowing due to a spontaneously generated coherence effect

We investigate the resonance fluorescence spectrum of an atomic three-level ladder system driven by two laser fields.We show that such a system emulates to a large degree a V-type atom with parallel dipole moments-the latter being a system that exhibits spontaneously generated coherence and can display ultrasharp spectral lines.We find a suitable energy scheme in a 85Rb atom and experimentally observe the narrowing of the central peak in a rubidium atomic beam.The corresponding spectrum can convincingly demonstrate the existence of spontaneously generated coherence.     

双模纠缠相干光场与V型三能级原子相互作用系统的原子偶极压缩效应

采用求解Schroedinger方程和数值计算方法，研究了双模纠缠相干光场与V型三能级原子相互作用过程中原子偶极算符的压缩效应，结果表明：此压缩效应与双模纠缠光场的纠缠程度、失谐量相关联。     

Optical bistability via quantum interference from incoherent pumping and spontaneous emission

We theoretically investigate the optical bistability (OB) in a V-type three-level atomic system confined in a unidirectional ring cavity via incoherent pumping field. It is shown that the threshold of optical bistability can be controlled by the rate of an incoherent pumping field and by interference mechanism arising from the spontaneous emission and incoherent pumping field. We demonstrate that the optical bistability converts to optical multi-stability (OM) by the quantum interference mechanism.     

Subluminal to superluminal light propagation in a V-type three-level atomic system interacting with squeezed vacuum

We study the light propagation properties in a V-type three-level atomic system interacting with two independent broadband squeezed baths. Using the graphic method, the dependences of the absorption and the dispersion of the system on the coupling field strength, the incoherent pumping field strength and the intensity of the squeezed vacuum are analysed. The result shows that the probe pulse propagation can be changed from subluminal to superluminal speed.     

双模纠缠相干光场与Ⅴ型三能级原子相互作用系统的原子偶极压缩效应

采用求解Schrodinger方程和数值计算方法,研究了双模纠缠相干光场与Ⅴ型三能级原子相互作用过程中原子偶极算符的压缩效应,结果表明:此压缩效应与双模纠缠光场的纠缠程度、失谐量相关联.