We report on an experimental observation of bound states of solitons in a passively mode-locked fiber soliton ring laser. The observed bound solitons are stable and have discrete, fixed soliton separations that are independent of the experimental conditions.

We present a cooling method that should be generally applicable to atoms with narrow optical transitions. This technique uses velocity-selective pulses to drive atoms towards a zero-velocity dark state and then quenches the excited state to increase the cooling rate. We demonstrate this technique of quenched narrow-line cooling by reducing the 1D temperature of a sample of neutral ${}^{40}\mathrm{Ca}$ atoms. We cool selected velocities with the ${}^1{S}_0{(4s}^2{)}^3{P}_1\mathrm{}\left(4s4p\right)\mathrm{}$ 657-nm intercombination line and quench with the ${}^3{P}_1{\mathrm{}\left(4s4p\right)\mathrm{}}^1{S}_0\mathrm{}\left(4s5s\right)\mathrm{}$ intercombination line at 553 nm, which increases the cooling rate eightfold. Limited only by available quenching laser power, we have transferred 18% of the atoms from our initial 2-mK velocity distribution and achieved temperatures as low as 4 μK, corresponding to a $v_{\mathrm{rms}}$ of 2.8 cm/s or 2 recoils at 657 nm. This cooling technique, which is closely related to Raman cooling, can be extended to three dimensions.

The fifth harmonic of a 60-fs 10-Hz terawatt titanium:sapphire laser generated in Xe gas is used to ionize Xe and Kr atoms by nonresonant two-photon absorption and Ar atoms through a quasiresonant three-photon process. At relatively low harmonic yields, the variation of the number of Kr and Xe ions with the number of harmonic photons is quadratic. At high harmonic yields, it deviates from a quadratic behavior, which we attribute to the influence of ionization in the harmonic process distorting the harmonic wave front. The two-photon ionization cross sections in Xe and Kr at 160 nm are found to be comparable.

A model of quantum measurement is proposed, which aims to describe statistical mechanical aspects of this phenomenon, starting from a purely Hamiltonian formulation. The macroscopic measurement apparatus is modeled as an ideal Bose gas, the order parameter of which, that is, the amplitude of the condensate, is the pointer variable. It is shown that properties of irreversibility and ergodicity breaking, which are inherent in the model apparatus, ensure the appearance of definite results of the measurement, and provide a dynamical realization of wave-function reduction or collapse. The measurement process takes place in two steps: First, the reduction of the state of the tested system occurs over a time of order $ħ{/(TN}^{1/4}),$ where T is the temperature of the apparatus, and N is the number of its degrees of freedom. This decoherence process is governed by the apparatus-system interaction. During the second step classical correlations are established between the apparatus and the tested system over the much longer time scale of equilibration of the apparatus. The influence of the parameters of the model on nonideality of the measurement is discussed. Schrödinger kittens, EPR setups, and information transfer are analyzed.

We present ab initio calculations of the complete gauge invariant set of the two-photon exchange graphs for the ${2p}_{1/2}-2s$ transition energy in Li-like high-$Z$ ions. The evaluation is carried out to all orders in $Z\alpha$ in the range $Z=20\mathrm{}–100.$ Results are compared with calculations based on relativistic many-body perturbation theory. All presently available contributions to the ${2p}_{1/2}-2s$ transition energy are collected. The resulting theoretical predictions are compared with experimental data.

The coherent states for the quantum Kepler motion proposed in our previous work [Phys. Rev. A 59, 1021 (1999)], which is based on the dynamical $\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(2\right)\mathrm{}$ symmetry and the Duru-Kleinert auxiliary time, are improved by making use of the theory of the conserved-charge coherent states formulated by Bhaumik et al. and by Skagertsam. The expectation values for the angular momentum and the Runge-Lenz-Pauli vector with respect to the improved Kepler coherent states are also discussed.

High-resolution spectroscopy of xenon is performed on four transitions from the ${5p}^6{}^1{S}_0$ ground state to the ${5d}^{\prime }[3/2{]}_1,$ $8d[1/2{]}_1,$ $8d[3/2{]}_1,$ and ${7s}^{\prime }[1/2{]}_1$ excited states $(jl$-coupling notation) by means of $1\mathrm{VUV}+1\mathrm{}\mathrm{UV}$ photoionization spectroscopy. Spectra of all nine stable isotopes are resolved enabling the determination of the hyperfine splittings and isotope shifts. Magnetic dipole (for both ${}^{129}\mathrm{Xe}$ and ${}^{131}\mathrm{Xe})$ and electric quadrupole (for ${}^{131}\mathrm{Xe})$ hyperfine splitting constants are derived for all four excited states. Mass and field shift contributions to the isotope shifts are separated using King plots relative to existing accurate isotope shift values. A high field shift factor, even for the transitions in which no s electron is involved, is deduced. From precise calibration of the transition frequencies an accurate value for the ionization energy of ${}^{136}\mathrm{Xe},$ $E_{3/2}^{136}=97\mathrm{}833.805\left(11\right)\mathrm{}\hspace{0.5em}{\mathrm{cm}}^{-1},$ is derived. In addition, values of the ionization energies for all other isotopes are determined.

We report on a study of electron-hydrogen scattering using a method [Bhatia, Schneider, and Temkin, Phys. Rev. Lett. 70, 1936 (1993)] that allows for the ab initio calculation of total and elastic cross sections at higher energies. In its general form the method uses complex-“radial” correlation functions, in a (Kohn) T-matrix formalism. The complex-correlation Kohn T-matrix method is reviewed in the context of electron-hydrogen scattering, including the derivation of the equation for the (complex) scattering function, and the extraction of the scattering information from the latter. The calculation reported here is restricted to S waves in the elastic region, where the correlation functions can be taken, without loss of generality, to be real. Phase shifts are calculated using Hylleraas-type correlation functions with up to 95 terms. Results are rigorous lower bounds; they are in general agreement with those of Schwartz [Phys. Rev. 124, 1468 (1961)], but they are more accurate and outside his error bounds at a couple of energies.

We study the localization properties of a one-dimensional incommensurate potential in the full quantum regime. In the system under consideration, and for amplitudes of the potential that are not too weak, the spectrum contains both localized and extended states, with one or more mobility edges. We show how these properties can be experimentally studied through the diffusion of wave packets in a one-dimensional incommensurate optical lattice.

We consider a gas of trapped Cooper-paired fermionic atoms that are manipulated by laser light. The laser induces a transition from an internal state with large negative scattering length (superfluid) to one with weaker interactions (normal gas). We show that the process can be used to detect the presence of the superconducting order parameter. Also, we propose a direct way of measuring the size of the gap in the trap. The efficiency and feasibility of this probing method is investigated in detail in different physical situations.

We consider the problem of Coulomb corrections to the inclusive cross section. We show that these corrections in the limiting case of small charge number of one of the nuclei coincide with those to the exclusive cross section. Within our approach we also obtain the Coulomb corrections for the case of large charge numbers of both nuclei.

It is shown that the vector potential of the Aharonov-Bohm effect is effectively the same as vector potentials of the quantum phases of electric and magnetic dipoles such as the Aharonov-Casher effect, when the Aharonov-Bohm solenoid is a straight cylinder with symmetric cross sections. With a circular cross section, the Aharonov-Bohm vector potential is effectively the same as the Aharonov-Casher vector potential, while with a rectangular cross section, it is effectively the same as the vector potential of the Casella phase. Therefore, we may say that the quantum phases of the dipoles belong to a subclass of the Aharonov-Bohm phase, and they must share the topological origin of the Aharonov-Bohm phase, even though their topological freedom is limited to the particle trajectories. However, the dipole phases have the extra relativistic effect that a magnetic (electric) dipole moving in an electric (magnetic) field feels an additional magnetic (electric) field, in its rest frame. This effect limits further the topological freedom of the dipole phases.

Numerical simulation has shown that a polymeric molecule can possess a photoinduced phenomenon—photoinduced polarization reversion—in which the electric dipole of the polymeric molecule is reversed by absorbing one photon. This paper provides an analytic theory by means of a response function to prove that a polymeric molecule with a bipolaron has a negative static polarizability and explains the physical origin of this photoinduced phenomenon in detail. This paper also presents a dynamical calculation for the photoinduced polarization reversion, from which the relaxation time for the dipole reversion can be determined.

Measurements of the energy loss and the energy-loss distributions of 160 GeV/amu fully stripped lead ions traversing a silicon single crystal are presented. The energy loss is measured using the silicon crystal as an intrinsic detector. Hence the measured energy loss is a restricted energy loss excluding very large energy transfers. For random incidence, the observed energy-loss distributions are very narrow and Gaussian-like. For well-channeled particles, the energy loss is strongly reduced as compared to so-called random particles. The observed energy loss is compared to calculations as well as simulations. Due to the small straggling, the energy-loss distributions are reflecting directly the distribution in transverse energy.

Sorting is a fundamental computational process that facilitates subsequent searching of a database. It can be thought of as factorization of the search process. The location of a desired item in a sorted database can be found by classical queries that inspect one letter of the label at a time. For an unsorted database, no such classical quick search algorithm is available. If the database permits quantum queries, however, then mere digitization is sufficient for efficient search. Sorting becomes redundant with the quantum superposition of states. A quantum algorithm is written down that locates the desired item in an unsorted database a factor of two faster than the best classical algorithm can in a sorted database. This algorithm has close resemblance to the assembly process in DNA replication.

We study the role of singlet coupling during double ionization of Helium atoms in intense laser fields, within the framework of the recollision model. The singlet cross sections for inelastic $\mathrm{e}+{\mathrm{He}}^{+}$ scattering, integrated over all excitation and ionization channels, are used. Nonadiabatic corrections during tunneling of the active electron are also included.

Using two radio frequency pulses separated in time we perform an amplitude division interference experiment on a rubidium Bose-Einstein condensate. The presence of a quantized vortex, which is nucleated by stirring the condensate with a laser beam, is revealed by a dislocation in the fringe pattern.

We describe a Raman scheme where the group velocity of an optical pulse can be altered dramatically. With this none electromagnetically-induced-transparency scheme, we show that when on a two-photon resonance, a light pulse can propagate with extremely slow group velocity. Both pulse narrowing and broadening can occur depending upon the choice of two-photon detuning. When using a tuned far-off two-photon resonance, we show that the pulse propagates “superluminally” in the medium with pulse narrowing.

Our recent results [N. L. Manakov et al., Phys. Rev. A 57, 3233 (1998); 61, 022103 (2000)] on the invariant representations of finite rotation matrices (FRM’s) of integer rank j (in terms of tensor products of vectors connected with a space-fixed reference frame) are generalized here for the general case of arbitrary (i.e., integer or half-integer) rank j. This extension is carried out by using new spinor representations of FRM’s in terms of specially introduced spinor-annihilation operators. We demonstrate that all widely used, standard representations of FRM’s follow as special cases of our invariant representation for particular parametrizations of the rotation parameters. As the simplest application of invariant spinor representations of FRM’s, the factorized form of Wigner ${\mathbf{d}}^j\left(\beta \right)$ matrices with an arbitrary rank j is obtained as a product of two triangular matrices composed of various powers of $\cos (\beta /2).\mathrm{}$