The master equation for a regularly pumped laser with coherent injection has been numerically solved using quantum trajectories. The onset of quadrature squeezing of the intracavity light has been observed. The case where the injection is switched well after the pumping has been considered.

The classical Mie theory for electromagnetic radiation scattering by homogeneous spherical particles is considered in the dielectric constant ($\epsilon$) $\to 0$ limit separately for the materials of the particles and the surrounding medium. The maxima of a scattered transverse electrical (TE) field for the surrounding medium materials with $\epsilon \to 0$ limits are investigated. The effective multipole polarizabilities of the corresponding scattering particles are investigated. The possibility of achieving magnetic dipole resonance and accordingly of constructing metamaterials with negative refractive index for aggregates of spherical particles in the surrounding medium with the dielectric constant near zero is demonstrated.

We report on an experimental violation of the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality using energy-time-entangled photons. The experiment is not free of the locality and detection loopholes but is the first violation of the Bell-CHSH inequality using energy-time entangled photons which is free of the postselection loophole described by Aerts et al. [Phys. Rev. Lett. 83, 2872 (1999)].

We derive an analytic formula which describes the final bound state dependence in ultracold three-body recombination. Using an energy-dependent loss parameter, the recently observed broad resonance in an ultracold gas of ${}^6\mathrm{Li}$ atoms [T. B. Ottenstein, T. Lompe, M. Kohnen, A. N. Wenz, and S. Jochim, Phys. Rev. Lett. 101, 203202 (2008); J. H. Huckans, J. R. Williams, E. L. Hazlett, R. W. Stites, and K. M. O’Hara, Phys. Rev. Lett. 102, 165302 (2009)] is described quantitatively. We also provide an analytic and approximation for the three-body recombination rate which encapsulates the underlying physics of the universal three-body recombination process.

We investigate the time evolution of the entanglement of assistance when one subsystem undergoes the action of local noisy channels. A general factorization law is presented for the evolution equation of entanglement of assistance. Our results demonstrate that the dynamics of the entanglement of assistance is determined by the action of a noisy channel on the pure maximally entangled state, in which the entanglement reduction turns out to be universal for all quantum states entering the channel. This single quantity will make it easy to characterize the entanglement dynamics of entanglement of assistance under unknown channels in the experimental process of producing entangled states by assisted entanglement.

We provide a class of initial encodings that can be sent with a high fidelity over an unmodulated, linear, $\mathit{XY}$ spin chain. As an example, an average fidelity of $96\%$ can be obtained using an 11-spin encoding to transmit a state over a chain containing 10 000 spins. An analysis of the magnetic-field dependence is given, and conditions for field optimization are provided.

We study two-body dipolar scattering with one dimension of confinement. We include the effects of confinement by expanding this degree of freedom in harmonic oscillator states. We then study the properties of the resulting multichannel system. We study the adiabatic curves as a function of $D/l$, the ratio of the dipolar and confinement length scales. There is no dipolar barrier for this system when $D/l<0.34$. We also study the WKB tunneling probability as a function of $D/l$ and scattering energy. This can be used to estimate the character of the scattering.

In this article we report ionization cross sections of neutral He, Ne, Ar, Kr, and Xe by impact of ${\mathrm{He}}^{+}$ ions with energies ranging from 25 to $1000$ keV/amu. A general theory to deal with dressed projectiles is developed in the context of the Continuum-Distorted-Wave Eikonal-Initial-State approximation. The strategy is based on the use of an effective charge defined in terms of the momentum transfer extracted from the first Born approximation and extensively used in the local plasma approximation to deal with ions in solids. The difference between the actual potential of the projectile and the Coulombic effective one used in the distorted wave functions is treated in first perturbative order. Our results show that the proposed approach gives a very good account of available experiments.

We study the role of propagation of strong x-ray free-electron laser pulses on the Auger effect. When the system is exposed to a strong x-ray pulse the stimulated emission starts to compete with the Auger decay. As an illustration we present numerical results for Ar gas with the frequency of the incident x-ray pulse tuned in the $2p_{3/2}–4s$ resonance. It is shown that the pulse propagation is accompanied by two channels of amplified spontaneous emission, $4s–2p_{3/2}$ and $3s–2p_{3/2}$, which reshape the pulse when the system is inverted. The population inversion is quenched for longer propagation distances where lasing without inversion enhances the Stokes component. The results of simulations show that the propagation of the strong x-ray pulses affect intensively the Auger branching ratio.

As a model for mesoscopic quantum systems in thermal contact, we consider a four-mode Bose-Hubbard model with two greatly differing tunneling rates. By a series of Holstein-Primakoff transformations, we show that the low-frequency dynamics of this system consists in general of two slow Josephson oscillations, rather than the single slow mode predicted by linear Bogoliubov theory. We identify the second slow Josephson oscillation as a heat exchange mode analogous to second sound.

Using the $\varepsilon$ expansion proposed in Y. Nishida and D. T. Son [Phys. Rev. Lett. 97, 050403 (2006)], we calculate the density correlation function and the dynamic structure function of the unitary Fermi gas at zero temperature to next-to-leading order in $\varepsilon$ for excitation energies below the quasiparticle threshold.

To test effective Hamiltonians for strongly interacting fermions in an optical lattice, we numerically find the energy spectrum for two fermions interacting across a Feshbach resonance in a double-well potential. From the spectrum, we determine the range of detunings for which the system can be described by an effective lattice model, and how the model parameters are related to the experimental parameters. We find that for a range of strong interactions the system is well described by an effective $t$-$J$ model, and the effective superexchange term, $J$, can be smoothly tuned through zero on either side of unitarity. Right at and around unitarity, an effective one-band general Hubbard model is appropriate, with a finite and small onsite energy, due to a lattice-induced anharmonic coupling between atoms at the scattering threshold and a weakly bound Feshbach molecule in an excited center-of-mass state.

We study a Bose-Einstein condensate of ${}^{52}\mathrm{Cr}$ atoms confined in a toroidal trap with a variable strength of $s$-wave contact interactions. We analyze the effects of the anisotropic nature of the dipolar interaction by considering the magnetization axis to be perpendicular to the trap symmetry axis. In the absence of a central repulsive barrier, when the trap is purely harmonic, the effect of reducing the scattering length is a tuning of the geometry of the system from a pancake-shaped condensate when it is large to a cigar-shaped condensate for small scattering lengths. For a condensate in a toroidal trap, the interaction in combination with the central repulsive Gaussian barrier produces an azimuthal dependence of the particle density for a fixed radial distance. We find that along the magnetization direction the density decreases as the scattering length is reduced but presents two symmetric density peaks in the perpendicular axis. For even lower values of the scattering length we observe that the system undergoes a dipolar-induced symmetry breaking phenomenon. The whole density becomes concentrated in one of the peaks, resembling an origin-displaced cigar-shaped condensate. In this context we also analyze stationary vortex states and their associated velocity fields, finding that these also show a strong azimuthal dependence for small scattering lengths. The expectation value of the angular momentum along the $z$ direction provides a qualitative measure of the difference between the velocity in the different density peaks.

We investigate a bosonic quantum gas consisting of two interacting species in an optical lattice at zero and finite temperature. The equilibrium properties and dynamics of this system are obtained by means of the Gutzwiller mean-field method. In particular we model recent experiments where the ramp-up of the optical lattice occurs on a time scale comparable to the tunneling time of the bosons. We demonstrate the violation of adiabaticity of this process with respect to the many-body quantum states, and we reproduce and explain the oscillations of the visibility as a function of ramp-up time, as seen in experiments.

We show that the adiabatic dynamics of a Bose-Einstein condensate (BEC) in a double-well potential can be described in terms of a dark variable resulting from the combination of the population imbalance and the spatial atomic coherence between the two wells. By means of this dark variable, we extend, to the nonlinear matter-wave case, the recent proposal by Vitanov and Shore [Phys. Rev. A 73, 053402 (2006)] on adiabatic passage techniques to coherently control the population of two internal levels of an atom or molecule. We investigate the conditions to adiabatically split or transport a BEC as well as to prepare an adiabatic self-trapping state by the optimal delayed temporal variation of the tunneling rate via either the energy bias between the two wells or the BEC nonlinearity. The emergence of nonlinear eigenstates and unstable stationary solutions of the system as well as their role in the breaking down of the adiabatic dynamics is investigated in detail.

The Debye series is developed for scattering of light by a homogeneous nonspherical particle to interpret the angular dependence of the scattered intensity in terms of various physical processes. In contrast to the previously developed Debye series for several regularly shaped particles that mirror the orthogonal curvilinear coordinate system where the variable-separation method can be applied, we develop and verify the Debye series in a coordinate-independent way using the extended boundary condition method. Verification computations are made for an oblate spheroidal water droplet of equivalent-volume sphere radius 10 $\mu$m.

We have measured sub-shot-noise quantum correlations of spatial fluctuations in the far-field image of the parametric fluorescence created in a type I $\beta$-barium-borate nonlinear crystal, either between opposite angular sectors (nondegenerate configuration) or between opposite pixels (degenerate configuration). Imaging is performed at a very low light level ($0.2$ photons per pixel) with an electron-multiplying CCD camera, resulting in purely spatial coincidences between single photons when detecting on pixels. Experimental results overcome the standard quantum-limit-shot-noise level without subtraction of the variance of the detection noise. We compare these experimental results with numerical results given by the quantum Green’s function method, which is proved to have strong advantages over stochastic simulations.

We present a series of analytical solutions which describe nonautonomous solitons in a planar waveguide with an additional periodical structure, that is, a long-period grating. The explicit functions which describe the evolution of the width, peak, and trajectory of the soliton’s wave center are presented exactly. The gain parameter has no effects on the motion of the soliton’s wave center or its width; it affects just the evolution of the soliton’s peak. The grating term affects the motion of the soliton’s wave center without changing its shape. The evolution of the soliton under the propagation-distance-dependent gain term is investigated too. It is reported that an arbitrary additional structure can be added on the graded-index waveguide to control the motion of the soliton without affecting its shape.

We analyze the symmetry breaking of matter-wave solitons in a pair of cigar-shaped traps coupled by tunneling of atoms. The model is based on a system of linearly coupled nonpolynomial Schrödinger equations. Unlike the well-known spontaneous-symmetry-breaking (SSB) bifurcation in coupled cubic equations, in the present model the SSB competes with the onset of collapse in this system. Stability regions of symmetric and asymmetric solitons, as well as the collapse region, are identified in the system’s parameter space.

We show that the rough surface of a microtoroidal cavity (scattering strength) can play a constructive role by studying the entanglement of two atoms surrounding the cavity. Analytical results show that appropriate surface roughness can enhance the atomic entanglement. In particular, the rough surface can also compensate for the loss of maximal entanglement during the evolution caused by cavity leakage and atomic spontaneous emission.