Clouds of ultracold strontium $5s48s{}^1{S}_0$ or $5s47d{}^1{D}_2$ Rydberg atoms are created by two-photon excitation of laser-cooled $5s^2{}^1{S}_0$ atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-$\ell$) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the $S$ states, which display isotropic attractive interactions, than for the $D$ states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

We consider the rotational excitation of molecules induced by asymmetric (“half-cycle”) as well as symmetric single-cycle THz pulses, leading to field-free time-dependent orientation. We show that the basic excitation mechanisms are very similar for the two types of pulses; i.e., the frequency distributions of the pulses at the rotational resonance frequencies play an important role. Furthermore, we investigate the interference between multiple rotational excitation pathways following prealignment with a nonresonant 800-nm femtosecond pulse. It is shown that such interference can lead to an enhancement of the orientation of the linear HCN molecule by a factor close to 2.

We derive solitary-wave solutions within the mean-field approximation in quasi-one-dimensional binary mixtures of Bose-Einstein condensates under periodic boundary conditions, for the case of an effective repulsive interatomic interaction. The particular gray-bright solutions that give the global energy minima are determined. Their characteristics and the associated dispersion relation are derived.

We study the effects of spontaneous symmetry breaking (SSB) in solitons composed of a dipolar Bose-Einstein condensate trapped in a dual-core system with dipole-dipole interactions (DDIs) and hopping between the cores. Two realizations of such a matter-wave coupler are introduced: weakly and strongly coupled. The former is based on two parallel pipe-shaped traps, whereas the latter is represented by a single pipe sliced by an external field into parallel layers. The dipoles are oriented along the axes of the pipes. In these systems, the dual-core solitons feature SSB of the supercritical and subcritical types, respectively. Stability regions are identified for symmetric and asymmetric solitons and nonbifurcating antisymmetric solitons, as well as for symmetric flat states, which may also be stable in the strongly coupled system due to competition between the attractive and repulsive intracore and intercore DDIs. The effects of the contact interactions are considered too. Collisions between moving asymmetric solitons in the weakly symmetric system feature an elastic rebound, a merger into a single breather, and passage accompanied by excitation of intrinsic vibrations of the solitons for small, intermediate, and large collision velocities, respectively. A $\mathcal{PT}$-symmetric version of the weakly coupled system is considered briefly, which may be relevant for matter-wave lasers. Stability boundaries for $\mathcal{PT}$-symmetric and -antisymmetric solitons are identified.

We study a harmonically trapped highly oblate two-component Bose-Einstein condensate, which consists of both dipolar and scalar bosonic atoms. When the dipoles are polarized along the symmetry axis of the trap, the dipolar atoms’ density exhibits a flat-disk regime at the trap center. It is found that the dipolar component is easier to induce the first vortex when the trap is rotating about the symmetry axis, if the long-range dipolar interactions dominate over the contact interactions, and vice versa. Vortex lattices with the compensating triangular, square, and stripe structures can be formed respectively under rapid rotation. When the dipoles are polarized perpendicular to the rotation axis, the two components are generically phase separated into a kernel-shell structure due to the anisotropic dipole-dipole interactions. While the giant-hole states are induced under slow rotation, the compensating stripe vortex structures are stabilized under fast rotation. In particular, a stripe-splitting structure is found to be competing with the stripe ones. These features are expected to be observed in the mixture of ${}^{52}\mathrm{Cr}$ atoms in the two different spin states.

We demonstrate experimentally the broadband and adiabatic light transfer in coupled waveguides based on multiple stimulated Raman adiabatic passage. Our experimental platform utilizes planar-type reconfigurable optically induced waveguide arrays and allows for efficient and robust transfer of light from an input waveguide over multiple states (up to nine) to an output waveguide. The same waveguide structures are tested for two propagation wavelengths separated by more than 200 nm, proving the achromaticity of the transfer process.

The pulsed radiation field propagating in a thick resonant absorber induces the polarization (quantified by the induced atomic dipoles in optical domain or the induced nuclear transition moments in gamma domain), which is distributed oscillatorily along the absorber forming a sandwich of polarization layers with opposite phases. As a result, the reemitted, scattered fields in different layers interfere with the incident input field destructively or constructively, giving rise to the well-known dynamical beats of the output radiation. We propose a method how to force these layers in the sandwich to reemit in phase with the incident field, which results in a strong radiation burst of short duration at the output of the absorber. We demonstrate this method experimentally for the 14.4 keV nuclear transition in ${}^{57}$Fe.

Recent experimentation has revealed a discrepancy between the calculated and actual hyperfine structure of the ${}^{207}$Pb${}^{19}$F molecule. This discrepancy has been attributed to a misrepresentation of the parity for the ground-state PbF molecule. In a previously published work [Shafer-Ray, Phys. Rev. A 73, 034102 (2006)], we derived a formula for the electric-field-dependent $g$ factor of the ground-state PbF molecule with the misassigned parity. In this Addendum, we reformulate that work and derive the $g$ factor based on the corrected ground state. We discuss the impact of the corrected $g$ factor of the PbF molecule and conclude that the PbF molecule has a $g$ factor which can be small enough to perform an experiment sensitive to the electron's electric dipole moment.

In this paper, building on some recent progress combined with numerical techniques, we shed some light on how the nonlocality of symmetric states is related to their entanglement properties and on their potential usefulness in quantum information processing. We use semidefinite programming techniques to devise a device-independent classification of three 4-qubit states into two classes inequivalent under local unitaries and permutation of systems. We study nonlocal properties when the number of parties grows large for two important classes of symmetric states: $W$ states and GHZ states, showing that they behave differently under the inequalities we consider. We also discuss the monogamy arising from the nonlocal correlations of symmetric states. We show that although monogamy in a strict sense is not guaranteed for all symmetric states, strict monogamy is achievable for all Dicke states when the number of parties goes to infinity.

Theoretical rotationally elastic total cross sections for electron scattering from methanol over the incident energy range 0.1–2000 eV are presented. The computation of such cross sections for methanol is reported over such an extended energy range. We have employed two distinct formalisms to compute the cross sections across this energy range; between 0.1 eV and the ionization threshold of the target we have used the ab initio R-matrix method, while at higher energies the spherical complex optical potential method is invoked. The results from both formalisms match quite well at energies where they overlap and hence imply that they are consistent with each other. These total cross-section results are also in very good agreement with available experimental data and earlier theoretical data. The composite methodology employed here is well established and can be used to predict cross sections for other targets where data is scarce or not available.

We have investigated the ionization of H atoms by few-cycle XUV laser pulses, in particular the interference between electronic wave packets emitted at different time moments (temporal interference), and the interference between wave packets emitted at the same time, but following different paths (spatial interference). During the spatial interference, under appropriate conditions, the holographic mapping (HM) of the target atom's state is achieved, which has the potential to become a powerful tool to study atomic structure. First, by using classical trajectory Monte Carlo calculations, we have confirmed the existence of two distinct types of electron trajectories, which contribute to the formation of the HM interference pattern. Then, by using ab initio quantum-mechanical calculations, we have studied how the shape of the HM pattern is influenced by the laser pulse parameters. Finally, we have identified the optimal laser pulse parameters for the observation of the HM interference in the case of atomic species with an ionization potential close to 0.5 a.u.

We study the propagation of few-cycle optical solitons in nonlinear media with an anomalous, but otherwise arbitrary, dispersion and a cubic nonlinearity. Our approach does not derive from the slowly varying envelope approximation. The optical field is derived directly from Maxwell's equations under the assumption that generation of the third harmonic is a nonresonant process or at least cannot destroy the pulse prior to inevitable linear damping. The solitary wave solutions are obtained numerically up to nearly single-cycle duration using the spectral renormalization method originally developed for the envelope solitons. The theory explicitly distinguishes contributions between the essential physical effects such as higher-order dispersion, self-steepening, and backscattering, as well as quantifies their influence on ultrashort optical solitons.

We report on the observation of 19 interspecies Feshbach resonances in an optically trapped ultracold Bose-Fermi mixture of ${}^{133}\text{Cs}$ and ${}^6\text{Li}$ in the two energetically lowest spin states. We assign the resonances to $s$- and $p$-wave molecular channels by a coupled-channels calculation, resulting in an accurate determination of LiCs ground-state potentials. Fits of the resonance position based on the undressed asymptotic bound state model do not provide the same level of accuracy as the coupled-channels calculation. Several broad $s$-wave resonances provide prospects to create fermionic LiCs molecules with a large dipole moment via Feshbach association followed by stimulated Raman passage. Two of the $s$-wave resonances overlap with a zero crossing of the Cs scattering length, which offers prospects for the investigation of polarons in an ultracold Li-Cs mixture.

We report the experimental and theoretical study of two-body interactions in a ${}^6$Li-${}^{133}$Cs Fermi-Bose mixture. Using a translatable dipole trap setup, we have successfully trapped the two species in the same trap with temperatures of a few microkelvins. By monitoring atom number loss and interspecies thermalization, we identify five $s$-wave interspecies Feshbach resonances in the lowest two scattering channels. We construct a coupled channels model using molecular potentials to fit and characterize these resonances. Two of the resonances are as wide as 6 mT (60 G) and thus should be suitable for creating Feshbach molecules and searching for universal few-body scaling.

We discuss in detail the search for a permanent electric dipole moment (EDM) of the ${}^{199}\mathrm{Hg}$ atom reported by Griffith et al. [Phys. Rev. Lett. 102, 101601 (2009)]. The upper bound, $d{(}^{199}\text{Hg})<3.1\times {10}^{-29}$ $e$ cm (95$\%$ C.L.), is a factor of 7 improvement over the best previous EDM limit for ${}^{199}$Hg, provides the most sensitive probe to date for EDMs in diamagnetic atoms, and sets new limits on time-reversal symmetry violation in extensions to the standard model. This paper provides extensive discussion of the techniques used to search for the ${}^{199}\mathrm{Hg}$ EDM and the implications of the new ${}^{199}\mathrm{Hg}$ EDM limit for $\mathit{CP}$ violation in elementary particle interactions.

For a general complex scattering potential defined on a real line, we show that the equations governing invisibility of the potential are invariant under the combined action of parity and time-reversal ($\mathcal{P}\mathcal{T}$) transformation. We determine the $\mathcal{P}\mathcal{T}$-symmetric as well as non-$\mathcal{P}\mathcal{T}$-symmetric invisible configurations of an easily realizable exactly solvable model that consists of a two-layer planar slab consisting of optically active material. Our analysis shows that although $\mathcal{P}\mathcal{T}$ symmetry is neither necessary nor sufficient for the invisibility of a scattering potential, it plays an important role in the characterization of the invisible configurations. A byproduct of our investigation is the discovery of certain configurations of our model that are effectively reflectionless in a spectral range as wide as several hundred nanometers.

The transition from a gapless liquid to a gapped dimerized ground state that occurs in the frustrated antiferromagnetic Majumdar-Ghosh (or $J_1-J_2$ Heisenberg) model is revisited from the point of view of entanglement. We study the evolution of entanglement spectra, a “projected subspace” block entropy, and concurrence in the Schmidt vectors through the transition. The standard tool of Schmidt decomposition along with the existence of the unique Majumdar-Ghosh (MG) point where the ground states are degenerate and known exactly suggest the projection into two orthogonal subspaces that is useful even away from this point. Of these, one is a dominant five-dimensional subspace containing the complete state at the MG point and the other contributes marginally, albeit with increasing weight as the number of spins is increased. We find that the marginally contributing subspace has a minimum von Neumann entropy in the vicinity of the dimerization transition. Entanglement content between pairs of spins in the Schmidt vectors, studied via concurrence, shows that those belonging to the dominant five-dimensional subspace display a clear progress towards dimerization as the MG point is approached. In contrast, study of the Schmidt vectors in the marginally contributing subspace, as well as in the projection of the ground state in this space, display pair concurrence which decreases on both sublattices as the MG point is approached. The robustness of these observations indicate their possible usefulness in the study of models that have similar transitions, and have hitherto been difficult to study using standard entanglement signatures.

In this paper, we investigate the possibility of measuring the purity of a quantum state (and the overlap between two quantum states) within a minimal model where the measurement device is minimally composed. The minimality is based on the assumptions that (i) we use a yes-no measurement on a single system to determine the single value of the purity in order not to extract other redundant information and (ii) we use neither ancilla nor random measurement. We show that the measurability of the purity within this model critically depends on the parity of dimension of the quantum system: The purity measurement is possible for odd-dimensional quantum systems, while it is impossible for even-dimensional cases.

An analytic description of laser-assisted electron-atom scattering (LAES) in an elliptically polarized field is presented using time-dependent effective range (TDER) theory to treat both electron-laser and electron-atom interactions nonperturbatively. Closed-form formulas describing plateau features in LAES spectra are derived quantum mechanically in the low-frequency limit. These formulas provide an analytic explanation for key features of the LAES differential cross section. For the low-energy region of the LAES spectrum, our result generalizes the Kroll-Watson formula to the case of elliptic polarization. For the high-energy (rescattering) plateau in the LAES spectrum, our result generalizes prior results for a linearly polarized field valid for the high-energy end of the rescattering plateau [Flegel et al., J. Phys. B 42, 241002 (2009)] and confirms the factorization of the LAES cross section into three factors: two field-free elastic electron-atom scattering cross sections (with laser-modified momenta) and a laser field-dependent factor (insensitive to the scattering potential) describing the laser-driven motion of the electron in the elliptically polarized field. We present also approximate analytic expressions for the exact TDER LAES amplitude that are valid over the entire rescattering plateau and reduce to the three-factor form in the plateau cutoff region. The theory is illustrated for the cases of $e$-H scattering in a CO${}_2$-laser field and $e$-F scattering in a midinfrared laser field of wavelength $\lambda =3.5\mu$m, for which the analytic results are shown to be in good agreement with exact numerical TDER results.

We present an universal description for Lamb shift of a lossy two-level-emitter (TLE) inside a leaky cavity by combining the quantum dissipation theory and the perturbative treatment developed in cavity QED. The total spectrum function of bath associated with the TLE is deduced by the standard method developed for a quantum dissipation model, from which the total spontaneous emission rate and Lamb shift are calculated. The developed calculation scheme is able to reproduce the known Purcell enhancement factor and is shown to be in agreement with the analysis made for a confocal resonator. It is found that the Lamb shift due to a leaky cavity mode has a sharp drop when sweeping across the resonance point. The physics behind this unusual behavior and the related experimental observations made on both atom-cavity and quantum-dot cavity systems are also analyzed.