The bound-state energies and other properties are determined to high accuracy for the ground and first electron-excited $S(L=0\mathrm{})\mathrm{}$ states in the ${}^3{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-}$ and ${}^4{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-}$ helium-muonic atoms. Such highly accurate calculations are performed with the use of an advanced, recently developed, multibox variational approach. In particular the hyperfine splitting has been calculated for the ${1s}_{\mu }{2s}_e$-electron-excited states in both helium-muonic atoms. The corresponding hyperfine splittings for these states are ≈520.786 MHz ${(}^3{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-})$ and ≈558.055 MHz ${(}^4{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-}).\mathrm{}$ The analogous splittings for the ground states are $\Delta \nu {(}^3{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-})\approx 4166.393\mathrm{MHz}$ and $\Delta \nu {(}^4{\mathrm{He}}^{2+}{\mu }^{-}{e}^{-})\approx 4464.555\mathrm{MHz},$ respectively.

Every entangled state can be perturbed and stay entangled. For a large class of pure entangled states, which includes all bipartite and all maximally entangled ones, we show how large the perturbation can be. Maximally entangled states can be perturbed the most. For each entangled state in our class, we construct hyperplanes which sandwich the set of all separable states. As the number of particles, or the dimensions of the Hilbert spaces for two of the particles increases, the distance between two of these hyperplanes goes to zero.

Relativistic many-body calculations of van der Waals coefficients $C_6$ for dimers correlating to two ground-state alkaline-earth-metal atoms at large internuclear separations are reported. The following values and uncertainties were determined: $C_6=214\mathrm{}\left(3\right)\mathrm{}$ for Be, 627(12) for Mg, 2221(15) for Ca, 3170(196) for Sr, and 5160(74) for Ba in atomic units.

We investigate the classical dynamics of the Rydberg atom in circularly polarized laser fields, restricted to the two-dimensional plane of polarization. We use a Poincaré surface of section to study nonlinear resonance structures for optical frequency driving fields. We demonstrate the existence and morphology of these structures as the laser intensity transitions from moderate to intense.

Two independently prepared condensates can be combined into a single larger condensate by detection of their relative phase in an interference measurement.

We show that the problem of nonconservation of energy found in the spontaneous localization model developed by Ghirardi et al. [Phys. Rev. D 34, 470 (1986)] is very similar to the inconsistency between the stochastic models for turbulence and the Navier-Stokes equation. This sort of analogy may be useful in the development of both areas.

We study the decoherence properties of a two-qubit quantum swap gate in Milburn’s model of decoherence where the gate is realized by the quantum-dot system. We examine how the so-called intrinsic decoherence may degrade the gate purity and gate fidelity of the quantum swap gate and also present a potential source for the occurrence of Milburn’s equation in the system of concern.

Quantum-information processing is carried out using dipolar coupled spins and high-resolution nuclear magnetic resonance (NMR). The systems chosen are the dipolar coupled methyl protons of ${\mathrm{CH}}_3\mathrm{CN}$ partially oriented in a liquid crystalline matrix yielding a two-qubit system and dipolar coupled ${}^{13}\mathrm{C}$ and methyl protons of ${}^{13}{\mathrm{CH}}_3\mathrm{CN}$ also partially oriented in the liquid crystalline matrix, yielding a three-qubit system. The dipolar coupled protons of oriented ${\mathrm{CH}}_3$ group are chemically and magnetically identical and their eigenstates can be divided into a set of quartet states (symmetric A) and a pair of doublet (E) states. We describe here a method for selectively retaining the magnetization of the symmetric states, yielding two and three qubit systems. We create pseudopure states using single-quantum-transition selective pulses and implement two- and three-qubit gates using one- and two-dimensional NMR.

We study the deterministic entanglement of a pair of neutral atoms trapped in an optical lattice by coupling to excited-state molecular hyperfine potentials. Information can be encoded in the ground-state hyperfine levels and processed by bringing atoms together pairwise to perform quantum logical operations through induced electric dipole-dipole interactions. The possibility of executing both diagonal- and exchange-type entangling gates is demonstrated for two three-level atoms and a figure of merit is derived for the fidelity of entanglement. The fidelity for executing a CPHASE gate is calculated for two ${}^{87}\mathrm{Rb}$ atoms, including hyperfine structure and finite atomic localization. The main source of decoherence is spontaneous emission, which can be minimized for interaction times fast compared to the scattering rate and for sufficiently separated atomic wave packets. Additionally, coherent couplings to states outside the logical basis can be constrained by the state-dependent trapping potential.

Energies of ${3l3l}^{\prime }{3l}^{″}$ states of aluminumlike ions with $Z=14\mathrm{}–100$ are evaluated to second order in relativistic many-body perturbation theory starting from a ${1s}^2{2s}^2{2p}^6$ Dirac-Fock potential. Intrinsic three-particle contributions to the energy are included in the present calculation and found to contribute about 10–20 % of the total second-order energy. Corrections for the frequency-dependent Breit interaction and the Lamb shift are included in lowest order. A detailed discussion of contributions to the energy levels is given for aluminumlike germanium $\mathrm{}(Z=32\mathrm{}).$ Comparisons are made with available experimental data. We obtain excellent agreement for term splitting, even for low-Z ions. These calculations are presented as a theoretical benchmark for comparison with experiment and theory.

A two-dimensional three-boson system interacting with hard-core repulsion and trapped by parabolic confinement has been investigated. Two density functions associated with breathing motion and deformation, respectively, have been defined. Based on these density functions, the wave functions of low-lying states have been analyzed in detailed. The states are found to have explicit geometric features caused by the hard-core repulsion, these features depend strongly on the constraints imposed by symmetry. Striking similarity exists in the density functions, so that breathing bands can be well defined. A classification scheme is thereby proposed.

We report results of measurements and theoretical modeling of spontaneous spin polarization and associated hysteresis in an optically pumped Cs vapor. We observe hysteresis over the full range (20–450 torr) of ${\mathrm{N}}_2$ buffer gas pressures tested, and on two hyperfine components of the $D1\mathrm{}$ transition, so long as both electronic spin exchange and optical pumping of a resolved ground state hyperfine level take place faster than spin relaxation. On the $F=\overrightarrow{3}{F}_e=4\mathrm{}$ transition, the spin angular momentum is gained from the linearly polarized pump light, while on the $\overrightarrow{3}3$ transition, it comes instead from the buffer gas during collisional quenching. The density-matrix theoretical model we have developed includes the effects of coherence in the excited state. It reproduces all observed features of spontaneous polarization, including hysteresis curves in quantitative agreement with the data across a broad range of experimental parameters.

We implement a parallel, time-dependent hybrid finite-difference Lagrange mesh code to model the electron dynamics of the fixed-nuclei hydrogen molecular ion subjected to intense ultrashort laser pulses. Ionization rates are calculated and compared with results from a previous finite-difference approach and also with published Floquet results. The sensitivity of the results to the gauge describing the electron-field interaction is studied. Visualizations of the evolving wave packets are also presented in which the formation of a stable bound-state resonance is observed.

A theory of spontaneous parametric down-conversion, which gives rise to a quantum state that is entangled in multiple parameters, such as three-dimensional wave vector and polarization, allows us to understand the unusual characteristics of fourth-order quantum interference in many experiments, including ultrafast type-II parametric down-conversion, the specific example illustrated in this paper. The comprehensive approach provided here permits the engineering of quantum states suitable for quantum-information schemes and quantum technologies.

We investigate the dynamics of a micromaser continuously driven by a resonant coherent field and pumped by atoms injected in superposition states. We formulate a master equation for the system, and by a Monte Carlo wave-function approach we describe the steady-state behavior as a function of atomic-transit time or driving-field intensity. The combined action of polarized atoms and driving field can lead to enhancement or suppression of coherence in system dynamics, including nonclassical effects such as quadrature squeezing, sub-Poissonian photon statistics, and revival of Rabi oscillations, as well as to shifts of the induced cavity-field phase. These results show the possibility of manipulating both the photon number and the phase of the cavity field.

We investigate the single-atom detection system using an optical standing-wave cavity, from the viewpoint of the quantized center-of-mass motion of the atomic wave packet. We show that since the atom-field coupling strength depends upon the overlap integral of the atomic wave packet and the field mode function, the effect of the wave-packet spreading via the momentum exchange process brings about a significant effect in the detection efficiency. We find that, as a result, the detection efficiency is not sensitive to the individual atomic trajectory for reasonably slow atoms. We also address an interesting phenomenon of the atomic wave-packet splitting occurring when an atom passes through a node of the cavity field.

In this Brief Report, we present a geometric observation for the Bures fidelity between two states of a qubit.

We present a method for the approximate determination of one-electron effective potentials of many-electron systems from a finite number of values of the isotropic scattering factor. The method is based on the minimum cross-entropy technique. An application to some neutral ground-state atomic systems has been done within a Hartree-Fock framework.

We study the limitations on the relative number squeezing between photons and atoms coupled out from a homogeneous Bose-Einstein condensate. We consider the coupling between the translational atomic states by two photon Bragg processes, with one of the photon modes involved in the Bragg process in a coherent state and the other initially unpopulated. We start with an interacting Bose condensate at zero temperature and compute the time evolution for the system. We study the squeezing, i.e., the variance of the occupation number difference between the second photon and the atomic center-of-mass mode. We discuss how collisions between the atoms and photon rescattering affect the degree of squeezing which may be reached in such experiments.