Origination of entangled states upon interaction of atoms with narrow-band light

Generation and transformation of entangled states in a system of two-level atoms with relaxation interacting with light are considered. It is found that excitation by single-mode squeezed light produces mixed atomic states that prove to be nonseparable. For the field in the Fock state, there may arise Greenberger-Horne-Zeilinger states comprised of atoms and photons. On the basis of the exact solutions of the multiparticle problem, the generation and transformation of atomic states of the W class, including recording of the photon state, are discussed.     

Entangled light pulses from single cold atoms

The coherent interaction between a laser-driven single trapped atom and an optical high-finesse resonator allows one to produce entangled multiphoton light pulses on demand. The mechanism is based on the mechanical effect of light. The degree of entanglement can be controlled through the parameters of the laser excitation. Experimental realization of the scheme is within reach of current technology. A variation of the technique allows for controlled generation of entangled subsequent pulses, with the atomic motion serving as intermediate memory of the quantum state.     

Entangled states of light on the basis of biphotons

Systems for preparing entangled states of light from biphotons on the basis of linear optical elements and projective measurements are considered. Specific features of quantum correlations of the appearing states can be detected in the proposed detection schemes.     

GHZ类态原子与相干态场作用的原子偶极压缩

采用求解Schrodinger方程和数值计算的方法,研究了处于GHZ类态的三个全同二能级纠缠原子与相干态光场相互作用的原子偶极压缩特性,分析了光场的强弱和原子初始纠缠度对光场压缩特性的影响.计算和分析表明:系统的原子偶极压缩量随时间演化关系与作用光场的强弱和原子在初始时刻的纠缠程度有强烈的关联,原子偶极压缩程度随原子纠缠程度的增加而减弱.     

在与原子相互作用中光偏振态的量子描述及其演化

应用偏振光的量子理论和斯托克斯算符研究了无克尔媒质和存在克尔媒质情况下，光在与原子相互作用过程中偏振态的演化.研究了偏振光中斯托克斯参量的涨落及其压缩的非经典行为.偏振椭圆、量子光学中的偏振度和斯托克斯参量的信噪比也得到了讨论.结果表明斯托克斯参量及其涨落在时间演化中呈现出被调制的振荡，这些振荡表现出间歇地崩塌和恢复.在与原子的相互作用过程中，光的偏振椭圆不随时间变化，但偏振度却随时间出现振荡.克尔媒质对这些振荡演化有很大影响. 关键词： 斯托克斯算符 斯托克斯参量 量子偏振态 量子涨落     

Scattering of light exotic atoms in excited states

The differential and total cross-sections for the scattering of muonic, pionic, kaonic and antiprotonic hydrogen in excited states from atomic hydrogen have been calculated for the purpose of atomic cascade calculations. The scattering problem is treated in a fully quantum mechanical framework which takes the energy shifts and, in the case of the hadronic atoms, the widths of the ns states into account. The validity of semiclassical approximations is critically examined. Received 4 December 2001 and Received in final form 4 February 2002     

The electron-electron interaction in doubly-excited states of atoms

Doubly-excited states of the isoelectronic sequence of H⁻, in which both electrons are in high principal quantum numbers, are examined on the basis of alternative pictures of the correlations between the two electrons. Restricting ourselves to the lowest¹ S states with both electrons in principal quantum numbern, we parametrise the electron-electron interaction on the basis of these pictures and compare the resulting simple expressions with more elaborate numerical calculations. This provides further understanding of the nature of correlations in such states. 1984 JILA Visiting Fellow.     

Entangled states of light during its propagation in a transparent medium with cubic nonlinearity

When two coherent waves propagate in a transparent medium with cubic nonlinearity, a nonclassical state appears which is characterized by the quantum correlation of the waves. On the basis of exact solutions to the problem, it was found that such states lead to violation of the separability criterion for continuous variables.     

Resonant interaction of light with a thin film of three-level atoms

Refraction of a double-frequency optical pulse at the interface between two linear dielectrics containing a thin film of resonant atoms is considered. The dynamics of the system is treated based on the model of three-level atoms with the V-type energy diagram. Refraction of short and long (compared with the Rabi oscillation period) pulses is analyzed with allowance for local-field effects. In both cases, the shape of the pulse corresponding to one carrier wave frequency is shown to depend on the energy of the pulse with the other carrier wave frequency. In particular, both the frequency and the depth of the amplitude modulation arising in the refracted pulse are changed.     

Strong interaction shifts and widths in light kaonic atoms

Energy shifts and line widths of X-ray transitions in kaonic atoms have been measured with an accuracy of about 10%. These data have been interpreted in terms of an optical potential. Whereas earlier approaches based on the free K⁻N scattering lengths fail to reproduce the data, a set of effective parameters consistant with all now available experiments could be derived.     

Entangled coherent states under dissipation

We study the evolution of entangled coherent states of the two quantized electromagnetic fields under dissipation. Characteristic time scales for the decay of the negativity are found in the case of large values of the phase space distance among the states of each mode. We also study how the entanglement emerges among the reservoirs.     

类锂离子里德堡态中的自旋-其它轨道相互作用

以多电子原子精细结构哈密顿的球张量形式和三价原子的非相对论性能级结构理论为基础,借助不可约张量理论,建立了计算类锂离子里德堡态中的自旋-其它轨道相互作用能的一种解析理论形式.完成了所有的角向积分和自旋求和计算,自旋-其它轨道相互作用能最终用径向积分来表示.应用所建立的理论对类锂离子(1s2np)2Pj态的自旋-其它轨道相互作用能进行了具体分析.     

Freezing light with cold atoms

The impact of disorder and localisation in electronic conduction was introduced more than half a century ago by Philip Anderson. In a much broader context of disorder-mediated wave dynamics it remains an important research area, and surprises abound. Meanwhile, research in ultracold atomic physics has led to phenomenally detailed elucidation of properties, including changes in phase, of quantum degenerate Bosonic and Fermionic gases. For example, beautiful experiments have recently demonstrated, in quasi one-dimensional systems, Anderson localisation of matter waves. In this brief essay, we describe and discuss research on wave localisation in the context of ultracold atomic physics, with a particular emphasis on light localisation in ultracold and high-density atomic gases. Essential ideas are reviewed, along with the current experimental status of the field, and promising avenues for future research are discussed.     

Selective photochemical isotope “burning” upon the interaction of resonant laser radiation with atoms

The method of laser isotope separation based on selective excited-atom “burning” in a flow with buffer and reagent gases was implemented experimentally for zinc and rubidium. Selective excitation of isotopes was accomplished by the one-photon method using weak absorption lines and at the edge of the Doppler contour of atomic absorption with small isotope shift.     

Entangled light from white noise

An atom that couples to two distinct leaky optical cavities is driven by an external optical white noise field. We describe how entanglement between the light fields sustained by two optical cavities arises in such a situation. The entanglement is maximized for intermediate values of the cavity damping rates and the intensity of the white noise field, vanishing both for small and for large values of these parameters and thus exhibiting a stochastic-resonancelike behavior. This example illustrates the possibility of generating entanglement by exclusively incoherent means and sheds new light on the constructive role noise may play in certain tasks of interest for quantum information processing.     

Entangled quantum states as direction indicators

We consider the use of N spin-1/2 particles for indicating a direction in space. If N>2, their optimal state is entangled. For large N, the mean square error decreases as N-2 (rather than N-1 for parallel spins).     

Spectroscopic study of the formation of excited strontium ions upon interaction of electrons with metastable atoms

The interaction of electrons with metastable Sr atoms, as a result of which the latter are simultaneously ionized and excited, is investigated experimentally. The magnitudes of the interaction cross sections (reaching ≈5 × 10^?20 m² for the 5² S _1/2-3² P _3/2 transition in Sr II) and their energy dependences are determined. Possible mechanisms of this interaction are discussed.