It was demonstrated that the spin polarization of a ${{}^4\text{H}\text{e}}^{+}$ ion beam $\left(P_{{\text{He}}^{+}}\right)$ can be determined from the spin dependence of the electron emission in the deexcitation process of spin-polarized He metastable atoms (${\text{He}}^{\ast }$, $2{{}^{3}S}_1$) and spin-polarized ${\text{He}}^{+}$ ions on Fe (100) surfaces. On Fe (100) surfaces, both ${\text{He}}^{\ast }$ and ${\text{He}}^{+}$ deexcite via Auger neutralization, and therefore, the spin asymmetry obtained from spin-polarized ${\text{He}}^{+}$ ion neutralization spectroscopy should be equal to that from spin-polarized metastable ${\text{He}}^{\ast }$ deexcitation spectroscopy. The spin polarization of ${\text{He}}^{\ast }$ was obtained from Stern-Gerlach measurements. $P_{{\text{He}}^{\text{+}}}$ was finally determined to be $0.19\pm 0.02$.

The properties of the localized states of a two-component Bose-Einstein condensate confined in a nonlinear periodic potential (nonlinear optical lattice) are investigated. We discuss the existence of different types of solitons and study their stability by means of analytical and numerical approaches. The symmetry properties of the localized states with respect to nonlinear optical lattices are also investigated. We show that nonlinear optical lattices allow the existence of bright soliton modes with equal symmetry in both components and bright localized modes of mixed symmetry type, as well as dark-bright bound states and bright modes on periodic backgrounds. In spite of the quasi-one-dimensional nature of the problem, the fundamental symmetric localized modes undergo a delocalizing transition when the strength of the nonlinear optical lattice is varied. This transition is associated with the existence of an unstable solution, which exhibits a shrinking (decaying) behavior for slightly overcritical (undercritical) variations in the number of atoms.

On the basis of angular spectrum representation, the reversed propagation dynamics of a Laguerre-Gaussian beam in left-handed materials (LHMs) is presented. We show that the negative phase velocity gives rise to a reversed screw of the wave front, and ultimately leads to a reversed rotation of the optical vortex. Furthermore, the negative Gouy-phase shift causes an inverse spiral of the Poynting vector. It is found that the Laguerre-Gaussian beam in LHMs will present the same propagation characteristics as the counterpart with opposite topological charges in regular right-handed materials (RHMs). The momentum conservation theorem ensures that the tangential component of the wave momentum at the RHM-LHM boundary is conserved. It is shown that although the linear momentum reverses its direction, the angular momentum remains unchanged.

We investigate the quantum properties of the well-known process of sum frequency generation, showing that it is potentially a very useful source of nonclassical states of the electromagnetic field, some of which are not possible with the more common techniques. We show that it can produce quadrature squeezed light, bright bichromatic entangled states, and symmetric and asymmetric demonstrations of the Einstein-Podolsky-Rosen paradox. We also show that the semiclassical equations totally fail to describe the mean-field dynamics when the cavity is strongly pumped.

Mode-locked fiber lasers in which pulse shaping is based on filtering of a frequency-chirped pulse are analyzed with the cubic-quintic Ginzburg-Landau equation. An exact analytical solution produces a variety of temporal and spectral shapes, which have not been observed in any experimental setting to our knowledge. Experiments agree with the theory over a wide range of parameters. The observed pulses balance gain and loss as well as phase modulations, and thus constitute dissipative temporal solitons. The normal-dispersion fiber laser allows systematic exploration of this class of solitons.

Two schemes of projection measurement are realized experimentally to demonstrate the de Broglie wavelength of three photons without the need for a maximally entangled three-photon state (the NOON state). The first scheme is based on a proposal by [Wang and Kobayashi, Phys. Rev. A 71, 021802(R) (2005)] that utilizes a couple of asymmetric beam splitters while the second one applies the general method of NOON-state projection measurement to a three-photon case. Quantum interference of three photons is responsible for projecting out the unwanted states, leaving only the NOON-state contribution in these schemes of projection measurement. A detailed multimode analysis is made to account for imperfect situations in the experiments.

We have calculated the atomic electric dipole moments (EDMs) induced in ${}^{229}\text{P}\text{a}$ and ${}^{225}\text{A}\text{c}$ by their respective nuclear Schiff moments $S$. The results are $d\left({}^{229}\text{P}\text{a}\right)=-9.5\times {10}^{-17}\left[S/\left(e\text{fm}\right)\right]e\text{cm}=-1.1\times {10}^{-20}\eta e\text{cm}$ and $d\left({}^{225}\text{A}\text{c}\right)=-8.6\times {10}^{-17}\left[S/\left(e\text{fm}\right)\right]e\text{cm}=-0.8\times {10}^{-21}\eta e\text{cm}$. EDM of ${}^{229}\text{P}\text{a}$ is $3\times {10}^4$ times larger than ${}^{199}\text{H}\text{g}$ EDM and 40 times larger than ${}^{225}\text{R}\text{a}$ EDM. Possible use of actinides in solid state experiments is also discussed. The $\left(T,P\right)$-odd spin-axis interaction in RaO molecule is 500 times larger than in TlF.

Ontological theories of quantum mechanics describe a single system by means of well-defined classical variables and attribute the quantum uncertainties to our ignorance about the underlying reality represented by these variables. We consider the general class of ontological theories describing a quantum system by a set of variables with Markovian (either deterministic or stochastic) evolution. We provide proof that the number of continuous variables cannot be smaller than $2N-2$, $N$ being the Hilbert-space dimension. Thus, any ontological Markovian theory of quantum mechanics requires a number of variables which grows exponentially with the physical size. This result is relevant also in the framework of quantum Monte Carlo methods.

Nonproduct $n$-qubit pure states with maximum dimensional stabilizer subgroups of the group of local unitary transformations are precisely the generalized $n$-qubit Greenberger-Horne-Zeilinger states and their local unitary equivalents, for $n⩾3$, $n\ne 4$. We characterize the Lie algebra of the stabilizer subgroup for these states. For $n=4$, there is an additional maximal stabilizer subalgebra, not local unitary equivalent to the former. We give a canonical form for states with this stabilizer as well.

An excess noise in coherent-state preparation can prevent secure key distribution through lossy channel. The feasible single-copy and multicopy linear optical methods are proposed to purify the prepared state. The single-copy method always sufficiently reduces the excess noise to obtain the key secure against both the individual and collective attacks even through any lossy channel. To increase the secure key rate, two feasible applications of the multicopy linear optical purification are proposed. As a result, maximal secure key rate achievable through a given lossy channel can be approached.

We show that scalable multipartite entanglement among light fields may be generated by optical parametric oscillators (OPOs). The tripartite entanglement existent among the three bright beams produced by a single OPO—pump, signal, and idler—is scalable to a system of many OPOs by pumping them in cascade with the same optical field. This latter serves as an entanglement distributor. The special case of two OPOs is studied, as it is shown that the resulting five bright beams share genuine multipartite entanglement. In addition, the structure of entanglement distribution among the fields can be manipulated to some degree by tuning the incident pump power. The scalability to many fields is straightforward, allowing an alternative implementation of a multipartite quantum information network with continuous variables.

We examine how spectral entanglement in polarization-entangled photon states generated from bulk-crystal, spontaneous parametric down-conversion affects the success of entanglement swapping and type-I fusion gates. We quantify the success of the entanglement swapping and fusion gates by calculating the bipartite concurrence and residual tangle, respectively, in terms of the joint spectral probability amplitudes of the initial broad-bandwidth polarization-entangled states. We find that both polarization-entanglement measures depend strongly on the initial spectral entanglement, as well as on the configuration of the independent sources. Specifically, when spectral differences correlate with polarization, the optimal source configuration is different for the two protocols. We conclude that this distinction is founded in how the underlying Bell-state measurement and quantum-erasure techniques respond differently to distinguishing spectral information.

The coherent scattering spectrum of a three-level atom driven by an intense laser field with multiphoton resonant excitation is considered. The spectrum corresponding to harmonic generation is investigated both analytically and numerically for different initial atomic states. The analytical calculations are based on the generalized rotating wave approximation, which allows one to explain obtained spectra containing in general both even and odd harmonics. The results applied to the hydrogen atom show that one can achieve efficient generation of moderately high harmonics using multiphoton resonant excitation by appropriate laser pulses.

Studies of the $M1\text{−}E2$ interference effect in the mixed-type forbidden lines 461.5, 647.6, and 875.5 nm of Bi I are reported. A special computer program considering the interference effect was designed to obtain the predicted contours of the Zeeman structures of the lines. By variation of free parameters describing the line shapes and the electric-quadrupole admixtures, the calculated profiles were fitted to the recorded spectra. The $E2$ admixtures found are $\left(7.84\pm 0.14\right)\%$, $\left(17.5\pm 0.4\right)\%$, and $\left(0.70\pm 0.11\right)\%$ for the 461.5, 647.6, and 875.5 nm lines, respectively. Our results are compared with recent theories and other experiments.

We present a general formalism for describing stimulated Raman adiabatic passage in a multilevel atom. The atom is assumed to have two ground state manifolds $a$ and $b$ and an excited state manifold $e$, and the adiabatic passage is carried out by resonantly driving the $a\text{−}e$ and $b\text{−}e$ transitions with time-dependent fields. Our formalism gives a complete description of the adiabatic passage process and can be applied to systems with arbitrary numbers of degenerate states in each manifold and arbitrary couplings of the $a\text{−}e$ and $b\text{−}e$ transitions. We illustrate the formalism by applying it to both a simple toy model and to adiabatic passage in the cesium atom.

Certain proposed extended Bose-Hubbard models may exhibit topologically ordered ground states with excitations obeying non-Abelian braid statistics. A sufficient tuning of Hubbard parameters could yield excitation braiding rules allowing implementation of a universal set of topologically protected quantum gates. We discuss potential difficulties in realizing a model with a proposed non-Abelian topologically ordered ground state using optical lattices containing bosonic dipoles. Our direct implementation scheme does not realize the necessary anisotropic hopping, anisotropic interactions, and low temperatures.

We present how to control interactions between solitons, either bright or dark, in Bose-Einstein condensates by synchronizing Feshbach resonance and harmonic trap. Our results show that as long as the scattering length is to be modulated in time via a changing magnetic field near the Feshbach resonance, and the harmonic trapping frequencies are also modulated in time, exact solutions of the one-dimensional nonlinear Schrödinger equation can be found in a general closed form, and interactions between two solitons are modulated in detail in currently experimental conditions. We also propose experimental protocols to observe the phenomena such as fusion, fission, warp, oscillation, elastic collision in future experiments.

We calculated the equilibrium populations of spin components for a spin-1 Bose gas via the microcanonical distribution that assumes equal population of all the totally symmetric states. The eventual populations of the three spin components at equilibrium was found not to depend on the species and the details of the interactions, but to be fixed by the total magnetization of the system. The results agree well with experiments.

We present a proposal to manipulate the Goos-Hänchen shift of a light beam via a coherent control field, which is injected into a cavity configuration containing the two-level atomic medium. It is found that the lateral shifts of the reflected and transmitted probe beams can be easily controlled by adjusting the intensity and detuning of the control field. Using this scheme, the lateral shift at the fixed incident angle can be enhanced (positive or negative) under the suitable conditions on the control field, without changing the structure of the cavity.