We study a bosonic version of the Kondo lattice model with an onsite repulsion in the conduction band, implemented with alkali-metal atoms in two bands of an optical lattice. Using both weak- and strong-coupling perturbation theory, we find that at unit filling of the conduction bosons the superfluid-to-Mott-insulator transition should be accompanied by a magnetic transition from a ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator). Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that quantum spin fluctuations induced by the Kondo exchange cause the otherwise continuous superfluid-to-Mott-insulator phase transition to be first order. We show that lattice separability imposes a serious constraint on proposals to exploit excited bands for quantum simulations, and discuss a way to overcome this constraint in the context of our model by using an experimentally realized nonseparable lattice. A method to probe the first-order nature of the transition based on collapses and revivals of the matter-wave field is also discussed.

We investigate in detail the optimal conditions for a high fidelity transfer from a single-polariton state to a single-photon state and subsequent homodyne detection of the single photon. We assume that, using various possible techniques, the single polariton has initially been stored as a spin-wave grating in a cloud of cold atoms inside a low-finesse cavity. This state is then transferred to a single-photon optical pulse using an auxiliary beam. We optimize the retrieval efficiency and determine the mode of the local oscillator that maximizes the homodyne efficiency of such a photon. We find that both efficiencies can have values close to one in a large region of experimental parameters.

We demonstrate a harmonic-seeded switchable multiwavelength laser in air driven by intense midinfrared femtosecond laser pulses, in which population inversion occurs at an ultrafast time scale (i.e., less than ∼200 fs) owing to direct formation of excited molecular nitrogen ions by strong-field ionization of inner-valence electrons. The bright multiwavelength laser in air opens the perspective for remote detection of multiple pollutants based on nonlinear optical spectroscopy.

Composite quantum systems can be in generic states characterized not only by entanglement but also by more general quantum correlations. The interplay between these two signatures of nonclassicality is still not completely understood. In this work we investigate this issue, focusing on computable and observable measures of such correlations: entanglement is quantified by the negativity $\mathcal{N}$, while general quantum correlations are measured by the (normalized) geometric quantum discord $D_G$. For two-qubit systems, we find that the geometric discord reduces to the squared negativity on pure states, while the relationship $D_G\ge {\mathcal{N}}^2$ holds for arbitrary mixed states. The latter result is rigorously extended to pure, Werner, and isotropic states of two-qudit systems for arbitrary $d$, and numerical evidence of its validity for arbitrary states of a qubit and a qutrit is provided as well. Our results establish an interesting hierarchy, which we conjecture to be universal, between two relevant and experimentally friendly nonclassicality indicators. This ties in with the intuition that general quantum correlations should at least contain and in general exceed entanglement on mixed states of composite quantum systems.

We investigate schemes for Hamiltonian parameter estimation of a two-level system using repeated measurements in a fixed basis. The simplest (Fourier based) schemes yield an estimate with a mean-square error (MSE) that decreases at best as a power law $\sim N^{-2}$ in the number of measurements $N$. By contrast, we present numerical simulations indicating that an adaptive Bayesian algorithm, where the time between measurements can be adjusted based on prior measurement results, yields a MSE which appears to scale close to $\exp (-0.3N)$. That is, measurements in a single fixed basis are sufficient to achieve exponential scaling in $N$.

We study the transport of quantum correlations across a chain of interacting spin-$1/2$ particles. As a quantitative figure of merit, we choose a symmetric version of quantum discord and compare it with the transported entanglement, addressing various operating regimes of the spin medium. Discord turns out to be better transported for a wide range of working points and initial conditions of the system. We relate this behavior to the efficiency of propagation of a single excitation across the spin chain. Moreover, we point out the role played by a magnetic field in the dynamics of discord in the effective channel embodied by the chain. Our analysis can be interestingly extended to transport processes in more complex networks and the study of nonclassical correlations under general quantum channels.

We study the Ising spin chain with a Dzyaloshinskii-Moriya interaction, focusing on the static and dynamic properties of the entanglement entropy following a quantum quench. We show that the effects of the additional anisotropic interaction on the phase diagram and on the dynamics of the system are captured by the properties of the entanglement entropy. In particular, the model provides a way to study the quench dynamics in a system with an energy current. We consider quenches starting from an initial excited state of the Ising spin chain, and we analyze the effects of different initial conditions.

A time-dependent close-coupling method, formulated within the framework of a rotational function expansion in two-dimensional cylindrical coordinates, is used to investigate excitation processes in proton-lithium collisions. As a first check, the calculated $\text{Li}\left(1s^{2}2s\right)\to \text{Li}\left(1s^{2}2p\right)$ excitation cross sections are compared and shown to be in reasonable agreement with the previous Cartesian lattice time-dependent Schrödinger equation results for collision energies at 5, 10, and 15 keV. As a result, additional calculations are carried out to determine the cross sections not only for the $\text{Li}\left(1s^{2}2s\right)\to \text{Li}\left(1s^{2}2p\right)$ transitions, but also for the Li($1s^{2}3l$) transitions for a wider range of proton-impact energies from 2 to 50 keV. Reasonable agreement is found when further comparison of the dominant Li($1s^{2}2p$) excitation cross sections is made with data obtained from crossed-beams experiments and other close-coupling methods. With the present extensive and large-scale calculations, the convergence for the reported results is also addressed, especially for the less-dominant Li($1s^{2}3l$) transitions, with respect to the box sizes, number of coupled channels, and propagation time.

Reported are total, absolute charge-exchange cross sections for collisions of ${}^3$He${}^{2+}$ ions with He and H${}_2$. Measurements are reported at fixed energies between 0.33 and 4.67 keV/amu. Both the present results and earlier results of others are analyzed in terms of available experimental small-angle differential cross sections as a function of collision energy, and hence the geometry of the exit aperture of the gas-collision cells used by the various experimental groups. In addition, the effective length of gas-collision cells is studied using fluid dynamic and molecular flow simulations to address the density patterns near the cell entrance and exit apertures. When small acceptance-angle corrections were applied, the results of present and previous measurements for the single electron capture in these systems were brought into good accord in the relevant energy ranges. Taken in their entirety, the present data for ${}^3$He${}^{2+}$ with He and H${}_2$ lend themselves to new theoretical calculations of the multichannel charge-exchange cross sections.

Li${}^{+}$ ions with energies ranging from 0.3 to 2 keV are scattered from Au(110) and Pd(100) surfaces and from ultrathin Ag film grown on Au(111) in order to study electron transfer phenomena. We find that neutralization occurs quite efficiently and find an anomalous ion energy dependence of the neutral fraction for Au(110) and Pd(100) surfaces previously noted for Au(111). The dependence of the neutral fraction on the azimuthal angle of the Au(110) and Pd(100) surfaces is reported. In the case of Ag monolayer on Au(111), results are similar to the case of the Ag(111) surface. To understand the anomalous ion energy dependence, we present a theoretical study using density functional theory (DFT) and a linearized rate equation approach, which allows us to follow the Li charge state evolution for the (111) surfaces of Ag, Au, and Cu, and for the Ag-covered Au(111) surface.

We have applied a nonperturbative resonant theory to study the Rabi frequency of microwave multiphoton transitions between two Rydberg states of potassium in a static electric field. The Stark electric dipole moments used to calculate the Rabi frequency are determined by the Stark states' wave functions, which are obtained by the diagonalization method. The frequencies of the Rabi oscillations are in good agreement with either experimental ones or ones calculated by the time-dependent close-coupling method and the Floquet theory. Furthermore, we are able to show that the size of avoided crossings between the $(n+2)s$ and $(n,3)$ states can be predicted from the Stark electric dipole moment and the difference of the two Stark states' energy at a given resonance.

A theoretical study of Auger cascades during the decay of 3$p_{1/2}$ and 3$p_{3/2}$ vacancies in krypton has been performed by level-by-level calculations using a wide configuration interaction basis. Auger spectra for all steps of the cascades are presented and are compared with the existing experimental data. Good agreement of our results with the branching ratios of ions measured by a coincidence technique is obtained.

This paper analyzes the cooling of a single particle in a harmonic trap with red-detuned laser light with fewer approximations than previously done in the literature. We avoid the adiabatic elimination of the excited atomic state but are still interested in Lamb-Dicke parameters $\eta \ll 1$. Our results show that the Rabi frequency of the cooling laser can be chosen higher than previously assumed, thereby increasing the effective cooling rate but not affecting the final outcome of the cooling process. Since laser cooling is already a well-established experimental technique, the main aim of this paper is to present a model which can be extended to more complex scenarios, like cavity-mediated laser cooling.

We propose a method for systematically finding ground states of spinor Bose-Einstein condensates by utilizing the symmetry properties of the system. By this method, we can find not only an inert state, whose symmetry is maximal in the manifold under consideration, but also a noninert state, which has lower symmetry and depends on the parameters in the Hamiltonian. We establish the symmetry-classification method for the spin-1, 2, and 3 cases at zero magnetic field, and find an additional phase in the last case. The properties of the vortices in the spin-3 system are also discussed.

We report the calculation of heat capacity of an attractive Bose-Einstein condensate, with the number $N$ of bosons increasing and eventually approaching the critical number $N_{cr}$ for collapse, using the correlated potential harmonics (CPH) method. Boson pairs interact via the realistic van der Waals potential. It is found that the transition temperature $T_c$ initially increases slowly, then rapidly as $N$ becomes closer to $N_{cr}$. The peak value of heat capacity for a fixed $N$ increases slowly with $N$, for $N$ far away from $N_{cr}$. But after reaching a maximum, it starts decreasing when $N$ approaches $N_{cr}$. The effective potential calculated by the CPH method provides insight into this strange behavior.

In a recent work, we derived a formula for the elastic $s$-wave phase shifts for deep potentials with attractive tails vanishing faster than $1/r^2$ asymptotically [Phys. Rev. A 84, 032701 (2011)]. As an addendum to that work, we reformulate its key result, i.e., the formula for the scattering phase shift ${\delta }_0$, in such a way that the contributions independent of the short-range influence of the full potential are explicitly expressed in terms of the amplitudes for transmission through and quantum reflection by the nonclassical region of the potential tail.

We propose a Faraday anomalous dispersion optical filter (FADOF) based on a rare-earth ion doped crystal. We present theoretical analyses for the solid-state FADOF transmission. Our theoretical model predicts a maximum transmission efficiency of $71\%$ and a double-peaked transmission spectrum with a bandwidth of 6 GHz under current experimental conditions. Our proposal may have important applications in optical communications.

We investigate a hybrid optomechanical system composed of a micromechanical oscillator as a movable membrane and an atomic three-level ensemble within an optical cavity. We show that a suitably tailored cavity field response via electromagnetically induced transparency (EIT) in the atomic medium allows for strong coupling of the membrane's mechanical oscillations to the collective atomic ground-state spin. This facilitates ground-state cooling of the membrane motion, quantum state mapping, and robust atom-membrane entanglement even for cavity widths larger than the mechanical resonance frequency.

The relations between matrix elements of different ($P$,$T$)-odd weak interactions are derived. We demonstrate that similar relations hold for parity-nonconserving transition amplitudes and electron electric dipole moments (EDMs) of atoms and molecules. This allows one to express $P$- and $T$-odd effects in many-electron systems caused by different symmetry-breaking mechanisms via each other using simple analytical formulas. We use these relations for the interpretation of the anapole moment measurements in cesium and thallium and for the analysis of the relative contributions of the scalar-pseudoscalar $CP$-odd weak interaction and electron EDMs to the EDMs of Cs, Tl, Fr, and other atoms and many polar molecules (YbF, PbO, ThO, etc.). Model-independent limits on electron EDMs and the parameter of the scalar-pseudoscalar $CP$-odd interaction are found from the analysis of the EDM measurements for Tl and YbF.