We present angular distributions of photoelectrons of atomic model systems excited by intense linearly polarized laser pulses in the vuv and xuv regimes. We solve the multidimensional time-dependent Schrödinger equation for one particle on large spatial grids and investigate the direction dependence of the emitted electrons for isotropic $s$ states as well as $p$ states. Although the ponderomotive potential is small compared to the binding energy of the initially bound electron and the photon energy of the exciting laser field, richly structured photoelectron angular distributions are found which sensitively depend on the laser frequency and intensity as well as on the number of absorbed photons. The occurring shapes are explained in terms of scattering mechanisms.

For a three-cycle arbitrarily polarized laser pulse propagating in the $z$ direction, we calculate the $(q_x,q_y)$ momentum distribution for strong-field ionization of atomic hydrogen. We consider the Keldysh theory for a few-cycle pulse and compare the results obtained by evaluating the transition amplitude numerically with the results obtained by evaluating the transition amplitude using the saddle-point method. We show that the validity of the latter depends highly on the ellipticity for fixed peak intensity. This dependence and the range of applicability of the saddle-point method is qualitatively explained by a semiclassical model.

A method to produce a spin-dependent rotating potential using near-resonant circularly polarized laser beams is proposed. It is shown that half-quantum vortices are nucleated in a spinor Bose-Einstein condensate (BEC) with an antiferromagnetic interaction. In contrast to the vortex nucleation in a scalar BEC, the spin-vortex nucleation occurs at a low rotation frequency ($\simeq 0.1{\omega }_{\perp }$ with ${\omega }_{\perp }$ being the radial trap frequency) in a short nucleation time $\simeq 50\mathrm{ms}$ without dissipation. A method for nondestructive measurement of half-quantum vortices is discussed.

We give a detailed theoretical analysis of spontaneous periodic pattern formation in fiber lasers. The pattern consists of a bound state of hundreds of pulses in a ring fiber laser passively mode locked by nonlinear rotation of the polarization. The phenomenon is described theoretically using a multiscale approach to the gain dynamics: the fast evolution of a small excess of gain is responsible for the stabilization of a periodic pattern, while the slow evolution of the mean value of gain explains the finite length of the quasiperiodic soliton train. The resulting model is well adapted to experimental observations in a Er:Yb-doped double-clad fiber laser.

The differential virial theorem relates the force $-\partial V∕\partial \mathbf{r}$ associated with the one-body potential $V\left(\mathbf{r}\right)$ of density-functional theory to the Laplacian ${\nabla }^{2}n$ of the ground-state density $n\left(\mathbf{r}\right)$ and to a quantity ${\mathbf{z}}_s\left(\mathbf{r}\right)$ involving the kinetic energy density tensor $t_{\alpha \beta }\left(\mathbf{r}\right)$. Having the concept of the Pauli potential $V_P\left(\mathbf{r}\right)$, $z_s$ is derived for spherically symmetric ground-state densities $n\left(r\right)$ in terms of the von Weizsäcker kinetic energy density and the first derivative of $V_P\left(r\right)$. ${\mathbf{z}}_s$ is related solely to the gradient kinetic energy density $t_G\left(r\right)$ for Be-like atomic ions.

We study a simple system described by a $2\times 2$ Hamiltonian and the evolution of its quantum states under the influence of a perturbation. More precisely, when the initial Hamiltonian is not degenerate, we check analytically the validity of the adiabatic approximation and verify that, even if the evolution operator has no limit for adiabatic switchings, the Gell-Mann and Low formula allows the evolution of eigenstates to be followed. In the degenerate case, for generic initial eigenstates, the adiabatic approximation (obtained by two different limiting procedures) is either useless or wrong, and the Gell-Mann and Low formula does not hold. We show how to select initial states in order to avoid such failures.

We investigate numerically the time dependence of the multiple quantum coherences and entanglement in linear chains up to nine nuclear spins of $1∕2$ coupled by the dipole-dipole interactions. Two models are considered: (1) a spin chain with nearest-neighbor dipole-dipole interactions and (2) a more realistic model with interactions between all spins. It is shown that the entangled states appear between remote particles which do not interact directly (model 1), while the interaction between all spins (model 2) not always results in entanglement between remote spins.

An experimental and theoretical investigation of the dissociative states of $\mathrm{S}\mathrm{F}_4{}^{2+}$ is presented. Various two- and three-body decays have been investigated and an attempt has been made to assign the energy levels and the geometry of the dication.

The $4d$ photoabsorption spectra of ${\mathrm{I}}^{2+}$, ${\mathrm{I}}^{3+}$, and ${\mathrm{I}}^{4+}$ have been obtained in the $70–127\mathrm{eV}$ region with the dual laser-produced plasma technique at time delays ranging from $400\text{to}520\mathrm{ns}$. With decreasing time delay, the dominant contribution to the spectra evolves from the ${\mathrm{I}}^{2+}$ to the ${\mathrm{I}}^{4+}$ ions, and each spectrum contains discrete $4d\text{−}nf$ transitions and a broad $4d\text{−}\epsilon f$ shape resonance, which are identified with the aid of multiconfiguration Hartree-Fock calculations. The excited states decay by direct autoionization involving $5s$ or $5p$ electrons, and rates for the different processes and resulting linewidths were calculated. With increasing ionization, the $4d\text{−}\epsilon f$ shape resonance become intense and broader in going from ${\mathrm{I}}^{2+}$ to ${\mathrm{I}}^{3+}$, and then vanishes at ${\mathrm{I}}^{5+}$. In addition, the discrete structure of the calculated spectrum of each ion gradually approaches the corresponding shape resonance position. Based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we reproduced spectra which are in good agreement with experiment.

We investigate tunneling properties of Bogoliubov mode in a Bose-Einstein condensate. Using an exactly solvable model with a $\delta$-functional barrier, we show that each component in the two-component wave function $(u,v)$ of low-energy Bogoliubov phonon has the same form as the condensate wave function in the supercurrent state. As a result, the currents $J_u$ and $J_v$ associated with $u$ and $v$, respectively, have the same tunneling properties as those of supercurrent carried by condensate. Thus, the tunneling of low-energy Bogoliubov phonon described by the tunneling of these two currents shows perfect transmission. We also show that the supercurrent behaviors of Bogoliubov phonon still exist in the presence of supercurrent carried by condensate, except in the critical supercurrent state. In the critical current state, the perfect transmission is absent, because $J_u$ or $J_v$ exceeds their upper limit given by the critical value of the supercurrent associated with the condensate. Our results consistently explain the recently proposed two tunneling phenomena associated with Bogoliubov phonon, namely, the anomalous tunneling effect (perfect transmission in the low-energy limit) and the breakdown of the perfect transmission in the critical supercurrent state.

Optical binding is an optomechanical effect exhibited by systems of micro- and nanoparticles, suitably irradiated with off-resonance laser light. Physically distinct from standing-wave and other forms of holographic optical traps, the phenomenon arises as a result of an interparticle coupling with individual radiation modes, leading to optically induced modifications to Casmir-Polder interactions. To better understand how this mechanism leads to the observed assemblies and formation of patterns in nanoparticles, we develop a theory in terms of optically induced energy landscapes exhibiting the three-dimensional form of the potential energy field. It is shown in detail that the positioning and magnitude of local energy maxima and minima depend on the configuration of each particle pair, with regards to the polarization and wave vector of the laser light. The analysis reveals how the positioning of local minima determines the energetically most favorable locations for the addition of a third particle to each equilibrium pair. It is also demonstrated how the result of such an addition subtly modifies the energy landscape that will, in turn, determine the optimum location for further particle additions. As such, this development represents a rigorous and general formulation of the theory, paving the way toward full comprehension of nanoparticle assembly based on optical binding.

A probability density is proposed in complex space. This probability density is defined by replacing $x$ with $z$ in the Born probability density of quantum mechanics, and it is real valued and non-negative in complex space. In addition, the Eulerian rate equation for the probability density is derived, and the rate of change of the probability density is determined by the total energy density. Furthermore, this complex-extended Born probability density correctly reflects information of the trajectory dynamics for the wave function in complex space.

The all-order correlation potential method of accurate atomic structure calculations for atoms with one external electron is extended to include one more class of correlation diagrams to all orders. These are the so-called ladder diagrams, which describe residual Coulomb interaction between an external electron and atomic core. This is in addition to the screening of Coulomb interaction by core electrons and the hole-particle interaction in the core polarization operator, which are also included in all orders. Calculations of the energies of the lowest $s$, $p$, and $d$ states of cesium and thallium show that inclusion of the ladder diagrams leads to significant improvement of the accuracy of the calculations. The discrepancy between theoretical and experimental energies is reduced to a small fraction of 1% in all cases. This widens the range of atoms and atomic states for which the correlation potential method can produce very accurate results.

We demonstrate that it is possible to mold the flow of an electromagnetic (EM) beam in a magnetic photonic crystal by the application of a nonuniform external static magnetic field (ESMF). The beam bending can be understood and explained by analyzing the isofrequency (IF) curves. The effect of the ESMF on the shape and size of the IF curves enables the manipulation of the group velocity of the beam, resulting in the bending of the EM beam and creating a mirage effect.

The cofilamentation of two ultrashort laser pulses at 800 and $400\mathrm{nm}$ in argon is numerically shown to counteract their temporal splitting. The output pulses are as short as 15 and $6.5\mathrm{fs}$, respectively, without any postprocess compression or stringent alignment. The simultaneous generation of two sub-millijoule (160 and $15\mu \mathrm{J}$, respectively) sub-six-cycle pulses at $\omega$ and $2\omega$ is of particular interest for attosecond science.

We show that it is possible to employ reservoir engineering to turn two distant and relatively bad cavities into one good cavity with a tunable spontaneous decay rate. As a result, quantum computing schemes, which would otherwise require the shuttling of atomic qubits in and out of an optical resonator, can now be applied to distant quantum dots. To illustrate this we transform a recent proposal to entangle two qubits via the observation of macroscopic fluorescence signals [J. Metz et al., Phys. Rev. Lett. 97, 040503 (2006)] to the electron-spin states of two semiconductor quantum dots. Our scheme requires neither the coherent control of qubit-qubit interactions nor the detection of single photons. Moreover, the scheme is relatively robust against spin-bath couplings, parameter fluctuations, and the spontaneous emission of photons.

Above-threshold ionization electron spectra recorded with nonaligned molecules such as ${\mathrm{N}}_2$, $\mathrm{C}{\mathrm{O}}_2$, and ${\mathrm{C}}_3{\mathrm{H}}_4$ exhibit the same classical kinematics features of electrons in strong laser fields as for atoms in the ${10}^{14}\mathrm{W}{\mathrm{cm}}^{-2}$ laser intensity range. The cutoff energies for direct and rescattered electrons are governed by the electron classical dynamics in the intense laser field. The main differences are found in the energy-resolved angular distributions. The molecular potential leads to a larger differential elastic cross section for forward-rescattered electrons and as a consequence to broader angular distributions for rescattered electrons with energies lower than $5U_p$, where $U_p$ is the ponderomotive potential.

We investigate theoretically the extension of cavity optomechanics to multiple membrane systems. We describe the simplest case of two membranes in a cavity, in terms of the coupling of the light fields to the breathing and center-of-mass modes of the membrane array. We show that these normal modes can be optically addressed individually and also be cooled, trapped, and characterized, e.g., via quantum nondemolition measurements. The extension to a larger number of membranes is briefly discussed.

Recently, photon-subtracted Gaussian states (PSGSs), which well approximate superpositions of coherent states (SCSs) with small amplitudes, were generated by several experimental groups. We compare the ideal SCSs and the PSGSs for experimental tests of certain types of Bell inequalities. In particular, we analyze the effects of the key experimental components used to generate PSGSs: mixedness of the Gaussian states, limited transmittivity of the beam splitter, and an avalanche photodetector that cannot resolve photon numbers. As a result of this analysis, the degrees of mixedness and the beam splitter transmittivity that can be allowed for successful tests of Bell inequalities are revealed.