This paper investigates for the first time ever the use of the spin-orbit interaction to probe correlation effects in the generalized oscillator strength (GOS) of the $3d$ subshells of Cs, Ba, and Xe, viz. we study how the GOSs of the Cs, Ba, and $\mathrm{Xe}3d_{3∕2}$ and $3d_{5∕2}$ levels are affected by the intradoublet correlations. The calculations are carried out using the Hartree-Fock approximation and within the framework of a modified version of the spin-polarized random phase approximation with exchange, which takes into account multielectron correlation effects. The effects of relaxation of the excited electrons due to the creation of the $3d$ vacancy are also accounted for. Our GOS results for Cs, Ba, and Xe, obtained for values of the momentum transfer $q$ from 0 to 4 a.u. and energy transfer $\omega$ from 0.1 to 8 Ry, demonstrate the strong interaction between the components of the spin-orbit doublet of the $3d$ electrons in Cs, Ba, and Xe. This leads to the appearance of an additional maximum in the GOS for the $3d_{5∕2}$ subshell, due to the action of the $3d_{3∕2}$ electrons. Additionally, for the dipole transition in Cs and Ba, the $3d_{5∕2}$ subshell perturbs the $3d_{3∕2}$ strongly for $q=4$ a.u. only, while in Xe, the perturbation is at the $\omega$ value of approximately 58 Ry for all considered $q$ values. It is concluded that the intradoublet correlations are generally very important in the dipole, monopole, and quadrupole transitions, but particularly in the dipole transition.

Faddeev-Yakubovski equations are solved numerically for ${}^4\mathrm{He}$ tetramer and trimer states using realistic helium-helium interaction models. We describe the properties of ground and excited states, and we discuss with a special emphasis the ${}^4\mathrm{He}\text{−}{}^4\mathrm{He}_3$ low energy scattering.

It is shown that resonances in the unified recombination cross sections correspond directly to dielectronic satellite spectra. Positions, intensities, and profiles of satellite lines may be obtained accurately using the Breit-Pauli $R$-matrix method and the unified theory of total electron-ion recombination. The intrinsic dielectronic resonance strength corresponding to autoionizing resonances is defined in analogy with measured quantities, and with resonance oscillator strengths. Satellite intensities then depend extrinsically on dynamical parameters in the plasma and may be obtained at any temperature in a straightforward manner from the resonance strengths. Profiles of dielectronic satellite lines of He-like $\mathrm{Fe}\mathrm{XXV}$ and $\mathrm{Ni}\mathrm{XXVII}$ are obtained in an ab initio manner. Detailed calculations also exhibit interference effects in resonance profiles delineated at high resolution. Although interference among resonances is not important for resonance strengths of the highly charged ions $\mathrm{Fe}\mathrm{XXV}$ and $\mathrm{Ni}\mathrm{XXVII}$ it might be significant for lower ionization states of heavy elements in general. The resonance identitification scheme for unified recombination cross sections is described, and applied to obtain all known $KLL$ satellites of $\mathrm{Fe}\mathrm{XXV}$ and $\mathrm{Ni}\mathrm{XXVII}$. Dielectronic satellite strengths are compared with earlier works and significant differences and similarities are discussed.

The so-called March model of fullerene uses the one-center approximation of quantum chemistry to calculate the spherical $\pi$-electron density $\rho$ by the Thomas-Fermi (TF) statistical method. Then the variational principle of the TF theory is employed by combining the electronic energy determined entirely by $\rho$ with the discrete ${\mathrm{C}}_{60}$ nuclear potential energy to predict, semiquantitatively, the equilibrium radius. Here the same approach is worked out, but now largely analytically, in two dimensions, as a possible model of planar ring clusters. Again the equilibrium radii are calculated and consistency with realistic clusters of hydrogen and carbon rings is discussed in detail. Finally, an estimate of the “breathing” frequency of ${\mathrm{C}}_{14}$, ${\mathrm{C}}_{18}$, and ${\mathrm{C}}_{22}$ is given.

We analyze the efficiency of coherent population trapping (CPT) in a superposition of the ground states of three-level atoms under the influence of the decoherence process induced by a broadband thermal field. We show that in a single atom there is no perfect CPT when the atomic transitions are affected by the thermal field. The perfect CPT may occur when only one of the two atomic transitions is affected by the thermal field. In the case when both atomic transitions are affected by the thermal field, we demonstrate that regardless of the intensity of the thermal field the destructive effect on the CPT can be circumvented by the collective behavior of the atoms. An analytic expression was obtained for the populations of the upper atomic levels which can be considered as a measure of the level of thermal decoherence. The results show that the collective interaction between the atoms can significantly enhance the population trapping in that the population of the upper state decreases with an increased number of atoms. The physical origin of this feature is explained by the semiclassical dressed-atom model of the system. We introduce the concept of multiatom collective coherent population trapping by demonstrating the existence of collective (entangled) states whose storage capacity is larger than that of the equivalent states of independent atoms.

A unified approach to the calculation of dispersive forces on ground-state bodies and atoms is given. It is based on the ground-state Lorentz force density acting on the charge and current densities attributed to the polarization and magnetization in linearly, locally, and causally responding media. The theory is applied to dielectric macro- and micro-objects, including single atoms. Existing formulas valid for weakly polarizable matter are generalized to allow also for strongly polarizable matter. In particular when micro-objects can be regarded as single atoms, well-known formulas for the Casimir-Polder force on atoms and the van der Waals interaction between atoms are recovered. It is shown that the force acting on medium atoms—in contrast to isolated atoms—is in general screened by the other medium atoms.

The nonrelativistic ground-state energy of ${}^4\mathrm{He}{\mathrm{H}}^{+}$ is calculated using a variational method in Hylleraas coordinates. Convergence to a few parts in ${10}^{10}$ is achieved, which improves the best previous result of Pavanello et al. [J. Chem. Phys. 123, 104306 (2005)]. Expectation values of the interparticle distances are evaluated. Similar results for ${}^3\mathrm{He}{\mathrm{H}}^{+}$ are also presented.

We present two protocols, one for the storage of light in an atomic ensemble and the subsequent retrieval, and another one for the generation of entanglement between light and atoms. They rely on two passes of a single pulse through the ensemble, Larmor precessing in an external field. Both protocols work deterministically and the relevant figures of merit—such as the fidelity or the EPR variance—scale exponentially in the coupling strength. We solve the corresponding Maxwell-Bloch equations describing the scattering process and determine the resulting input-output relations which only involve one relevant light mode that, in turn, can be easily accessed experimentally.

With a femtosecond laser pulse we rapidly ionize potassium atoms $\left({\mathrm{K}}^0\right)$ in the gas phase, generating potassium ions $\left({\mathrm{K}}^{+}\right)$, and monitor the altered energy-level scheme with a subsequent hard x-ray pulse. Removal of the potassium $4s$ valence electron increases the binding energies of both the valence and the $1s$ core levels, and induces an ultrafast change of the $1s\text{−}4p$ x-ray transition energy by about $2.8\mathrm{eV}$. We simultaneously observe a 50% increase in oscillator strength of ${\mathrm{K}}^{+}$ over ${\mathrm{K}}^0$ for that transition.

In a recent experiment, Campbell et al. [Phys. Rev. Lett. 96, 020406 (2006)] observed degenerate four-wave mixing of matter waves in a one-dimensional optical lattice. We analyze the essential quantum features of the experiment to show that entanglement is created between the quadratures of the two scattered atomic clouds and is a true many-body (rather than two-body) phenomenon. We demonstrate that well-known bipartite entanglement inequalities are significantly violated and that this is robust to a moderate level of coherent seeding. The system is thus a promising candidate for generating spatially separated macroscopically entangled atomic samples.

We present a comprehensive theoretical study of vortex lattice formation in atomic Bose-Einstein condensates confined by a rotating elliptical trap. We consider rotating solutions of the classical hydrodynamic equations and their response to perturbations, as well as time-dependent simulations. We discriminate three distinct, experimentally testable, regimes of instability: ripple, interbranch, and catastrophic. Under symmetry-breaking perturbations these instabilities lead to lattice formation even at zero temperature. While our results are consistent with previous theoretical and experimental results, they shed further light on lattice formation.

We analyze the origin of interference disappearance in which-path double-aperture experiments. We show that we can unambiguously define an observable momentum transfer between the quantum particle and the path detector and we prove in particular that the so-called “momentum transfer free” experiments can be, in fact, logically interpreted in term of momentum transfer.

We propose a new method of quantization of a wide class of dynamical systems that originates directly from the equations of motion. The method is based on the correspondence between the classical and the quantum Poisson brackets, postulated by Dirac. This correspondence applied to open (non-Hamiltonian) systems allows one to point out the way of transition from the quantum description based on the Lindblad equation to the dynamical description of their classical analogs by the equations of motion and vice versa. As the examples of using of the method we describe the procedure of the quantization of three widely considered dynamical systems: (1) the harmonic oscillator with friction, (2) the oscillator with a nonlinear damping that simulates the process of the emergence of the limit cycle, and (3) the system of two periodic rotators with a weak interaction that synchronizes their oscillations. We discuss a possible application of the method for a description of quantum fluctuations in Josephson junctions with a strong damping and for the quantization of open magnetic systems with a dissipation and a pumping.

We study the preparation and distribution of high-fidelity multiparty entangled states via noisy channels and operations. In the particular case of Greenberger-Horne-Zeilinger and cluster states, we study different strategies using bipartite or multipartite purification protocols. The most efficient strategy depends on the target fidelity one wishes to achieve and on the quality of transmission channel and local operations. We show the existence of a crossing point beyond which the strategy making use of the purification of the state as a whole is more efficient than a strategy in which pairs are purified before they are connected to the final state. We also study the efficiency of intermediate strategies, including sequences of purification and connection. We show that a multipartite strategy is to be used if one wishes to achieve high fidelity, whereas a bipartite strategy gives a better yield for low target fidelity.

We demonstrate feedback control optimization for the Stark deceleration and trapping of neutral polar molecules using evolutionary strategies. In a Stark-decelerator beamline, pulsed electric fields are used to decelerate $\mathrm{OH}$ radicals and subsequently store them in an electrostatic trap. The efficiency of the deceleration and trapping process is determined by the exact timings of the applied electric field pulses. Automated optimization of these timings yields an increase of 40% of the number of trapped $\mathrm{OH}$ radicals.

We analyze the spectral properties of squeezed light produced by means of pulsed, single-pass degenerate parametric down-conversion. The multimode output of this process can be decomposed into characteristic modes undergoing independent squeezing evolution akin to the Schmidt decomposition of the biphoton spectrum. The main features of this decomposition can be understood using a simple analytical model developed in the perturbative regime. In the strong pumping regime, for which the perturbative approach is not valid, we present a numerical analysis, specializing to the case of one-dimensional propagation in a beta-barium borate waveguide. Characterization of the squeezing modes provides us with an insight necessary for optimizing homodyne detection of squeezing. For a weak parametric process, efficient squeezing is found in a broad range of local oscillator modes, whereas the intense generation regime places much more stringent conditions on the local oscillator. We point out that without meeting these conditions, the detected squeezing can actually diminish with the increasing pumping strength, and we expose physical reasons behind this inefficiency.

In this paper, we present results on the temporal coherence of the Ni-like palladium x-ray laser. We have modeled an experiment performed at the COMET laser facility (Lawrence Livermore National Laboratory), in order to investigate the coherence properties of the line at wavelength $14.68\mathrm{nm}$ ($4d{}^{1}S_0\to 4p{}^{1}P_1$ transition). To this end, a ray-tracing postprocessor is coupled to a collisional-radiative code. The effect of saturation on gain coefficient values is taken into account by developing a rigorous approach based on the Maxwell-Bloch formalism. The temporal coherence depends strongly on the shape and width of the amplified line. Our calculations give a coherence length of $290\mu \mathrm{m}$. While the full width at half maximum of the optically thin line is $28\mathrm{m}\mathrm{\AA }$, the amplified x-ray line exhibits a Gaussian profile and a width of $4\mathrm{m}\mathrm{\AA }$. Calculated coherence lengths and gains agree with measurements. Comparison with experiment is discussed.

A measurement of the natural linewidth of the $401\text{−}\mathrm{nm}$ $4f^{12}6s^2{}^3\mathrm{H}_6\to 4f^{12}\left({}^3\mathrm{H}_6\right)6s6p\left({}^1\mathrm{P}_1{}^o\right)$ $(6,1)_7{}^o$ transition in $\mathrm{Er}\mathrm{I}$ is presented. Using laser-induced fluorescence in an atomic beam, a linewidth of $(35.6\pm 1.2)\mathrm{MHz}$ is observed, a value that differs significantly from the literature value of $28\mathrm{MHz}$. This measurement provides an accurate determination of an essential laser cooling parameter that plays a central role in the development of laser cooling applications using Er atoms.