The laser cooling and trapping of ultracold neutral dysprosium has been demonstrated recently using the broad, open, 421-nm cycling transition. Narrow-line magneto-optical trapping of Dy on longer wavelength transitions would enable the preparation of ultracold Dy samples suitable for loading optical dipole traps and subsequent evaporative cooling. We have identified the closed 741-nm cycling transition as a candidate for the narrow-line cooling of Dy. We present experimental data on the isotope shifts, the hyperfine constants $A$ and $B$, and the decay rate of the 741-nm transition. In addition, we report a measurement of the 421-nm transition’s linewidth, which agrees with previous measurements. We summarize the laser-cooling characteristics of these transitions as well as other narrow cycling transitions that may prove useful for cooling Dy.

Low-energy dissociative electron attachment to uracil molecules in the gas phase is partly controlled by interaction between the lowest ${\sigma }^{*}$ resonance with a dipole-supported anion state. We calculate this contribution using a combination of the finite element discrete model with the resonance $R$-matrix theory. Deuterated uracil is investigated, also, and a strong isotope effect is found. The results agree qualitatively and semiquantitatively with experimental data, but for a complete description of the process the interaction between a second N—H bond ${\sigma }^{*}$ resonance in the molecule and the second ${\pi }^{*}$ resonance should be included.

The time (i.e., integrated charge) dependence of electron transmission through a single glass macrocapillary was studied for incident 500- and 800-eV electrons at different capillary tilt angles. As the transmitted intensity goes to equilibrium, the centroid energies and corresponding energy values of the full width at half maximum of the transmitted electron distributions are found to vary in phase and out of phase with the transmitted intensity, respectively. Stable equilibrium was not fully reached even for large integrated charge due to sharp oscillations in the transmitted intensity. Plots of the recovery charging curves after breakdown show larger charge constants for the first recovery, but subsequently show smaller values that are about equal to one another for a given beam energy. Previously, such oscillations and recovery have not been reported for electrons.

We investigate the possibility of forming high-fidelity atomic Fock states by gradual reduction of a quasi-one-dimensional trap containing spin-polarized fermions or strongly interacting bosons in the Tonk-Girardeau regime. Making the trap shallower and simultaneously squeezing it can lead to the preparation of an ideal atomic Fock state as one approaches either the sudden or the adiabatic limits. Nonetheless, the fidelity of the resulting state is shown to exhibit nonmonotonic behavior with the time scale in which the trapping potential is changed.

We propose the design of a field-free quantum cogwheel from a single linear molecule. The construction of the cogwheel is based on rotational states featuring both a simultaneous delocalized distribution along several chosen directions and a global rotational motion. Using adiabatic passage techniques, we shape control fields that could be implemented with the state-of-the-art technology to reach the proposed state. Unlike conventional molecular rotors whose electronic structure is chosen to mimic a classical motion, which requires complex molecules, the proposed quantum cogwheel is based on the controlled delocalization of a rotational wave packet.

We have studied the details of the formation of mutually guided and localized structures of co-propagating coherent electromagnetic radiation and a Bose-Einstein condensate (BEC). In the limit of zero temperature and large detuning, we have used a semiclassical model based on Maxwell equations coupled to the Schrödinger equation which includes the back action of the atoms on the radiation. Following numerically the two systems, we have found that a variety of effects can be displayed depending on the initial conditions: The formation of single-hump mutually guided structures of atoms and radiation seems to be only one of the possible outcomes of the interaction. Other effects we have observed via numerical simulations are, for instance, the creation of atom-laser solitarylike structures which are then symmetrically ejected from the initial central peak or similar symmetrical structures trapped in a bound state and thus oscillating about the central point in a way somehow reminiscent of purely nonlinear optics effect.

We study the dynamics of Bose-Einstein condensates in tilted and driven optical superlattices. For a bichromatic lattice, each Bloch band splits up into two minibands such that the dynamics is governed by the interplay of Bloch oscillations and transitions between the bands. Thus, bichromatic potentials provide an excellent model system for the study of nonlinear Landau-Zener tunneling, and they allow for a variety of applications in matter-wave interferometry and quantum metrology. In the present paper, we investigate the coherent dynamics of an interacting Bose-Einstein condensate as well as its stability. Different mechanisms of instability are discussed, which lead to a rapid depletion of the condensate.

We study how the bosonic atoms on the excited $p$ band of an optical lattice are coupled to the lowest $s$ band and the second excited $d$ band. We find that in some parameter regimes, the atom-atom interactions can cause a dynamical instability of the $p$-band atoms toward decay to the $s$ and $d$ bands. Furthermore, even when dynamical instability is not expected $s$ and $d$ bands can become substantially populated. We also find that the stability properties of the excited bands can be improved in superlattices.

We study the nonequilibrium dynamics of a many-body bosonic system on a lattice, subject to driving and dissipation. The time evolution is described by a master equation, which we treat within a generalized Gutzwiller mean field approximation for density matrices. The dissipative processes are engineered such that the system, in the absence of interaction between the bosons, is driven into a homogeneous steady state with off-diagonal long-range order. We investigate how the coherent interaction affects the properties of the steady state of the system qualitatively and derive a nonequilibrium phase diagram featuring a phase transition into a steady state without long-range order. The phase diagram also exhibits an extended domain where an instability of the homogeneous steady state gives rise to a persistent density pattern with spontaneously broken translational symmetry. In the limit of low particle density, we provide a precise analytical description of the time evolution during the instability. Moreover, we investigate the transient following a quantum quench of the dissipative processes and we elucidate the prominent role played by collective topological variables in this regime.

($n$ $+$ 1)-dimensional gated fluorescence signals induced by $n$ impulsive pulses are calculated using a superoperator formalism. The signals are given by a time-and-frequency convolution of a bare signal, expressed in terms of multipoint dipole correlation functions, with a gating spectrogram. Different groups of quantum pathways can be separated by their variation with the phases of the pulses (phase cycling), as is commonly done in nuclear magnetic resonance. Comparison is made with heterodyne-detected coherent signals.

We introduce an adiabatic quantum state transfer scheme in a nonuniform coupled triple-quantum-dot system. By adiabatically varying the external gate voltage applied on the system, the electron can be transferred between two spatially separated dots. We numerically study the effect of the system parameters on transfer fidelity and find a perfect matching between them. We also find that there is a relatively large tolerance range of difference between two coupling constants to permit high-fidelity quantum state transfer.

In this Brief Report, we investigate the generation of bright quadripartite entanglement of continuous variables in an experimentally realizable system involving second-order harmonic generation with competing nondegenerate optical parametric downconversion. By using the well-known van Loock–Furusawa criterion for continuous variable correlations, we find that the genuine quadripartite entanglement can be generated in the system over a wide range of controllable parameters. Besides this, it is shown that the bipartite entanglement between any two field modes can be achievable. In addition, the dependence of the quantum correlations on the pump parameter is also discussed.

We show that the presence of a background medium and a boundary surface or surfaces in cavity QED produces no change in the energy shift of a free charged particle due to its coupling to the fluctuating electromagnetic field of the vacuum. This clarifies that the electromagnetic and the observed mass of the charged particle are not affected by the modification of the field of the vacuum. The calculations are nonrelativistic and restricted to the dipole approximation but are otherwise based on the general requirements of causality.

Twisted photons offer a high-dimensional Hilbert space with the degree of freedom of orbital angular momentum (OAM). Entanglement swapping allows entangling photons that never interact. We report in this paper the hybrid entanglement swapping from multiphoton spin-entangled states to multiphoton OAM entangled states with the aid of $N$-pair hybrid spin-OAM entangled photons. Our scheme provides a feasible method for creating the two-photon OAM Bell states $(N=2)$ or multiphoton multidimensional OAM Greenberger-Horne-Zeilinger states $(N\ge 3)$. We highlight the advantage of multiparticle, multidimensional entangled states in some applications of quantum information protocols.

The photon-echo quantum memory is based on a controlled rephasing of the atomic coherence excited by a signal light field in the inhomogeneously broadened resonant line. Here, we demonstrate an active mechanism of the atomic rephasing that provides a perfect retrieval of the stored light field in the photon-echo quantum memory based on the use of arbitrary initial inhomogeneous broadening of the resonant line. We show that the rephasing mechanism can exploit all resonant atoms, thereby maximally increasing an optical depth of the resonant transition, which is one of the critical parameters for the realization of highly efficient quantum memory. We also demonstrate that the rephasing mechanism can be used for various realizations of the photon-echo quantum memory, thereby creating many possibilities for its practical realization.

We have studied transition metal clusters from a quantum information theory perspective using the density-matrix renormalization group (DMRG) method. We demonstrate the competition between entanglement and interaction localization and discuss the application of the configuration interaction-based dynamically extended active space procedure, which significantly reduces the effective system size and accelerates the speed of convergence for complicated molecular electronic structures. Our results indicate the importance of taking entanglement among molecular orbitals into account in order to devise an optimal DMRG orbital ordering and carry out efficient calculations on transition metal clusters. Apart from these algorithmic observations, which lead to a recipe for black-box DMRG calculations, our work provides physical understanding of electron correlation in molecular and cluster structures in terms of entropy measures of relevance also to recent work on tensor-network representations of electronic states. We also identify those molecular orbitals which are highly entangled and discuss the consequences for chemical bonding and for the structural transition from an dioxygen binding copper cluster to an bis-oxygen-bridged system with broken O–O bond.

A directly approximated exchange-correlation potential should, by construction, be a functional derivative of some density functional in order to avoid unphysical results. Using generalized gradient approximations (GGAs) as an example, we show that functional derivatives of explicit density functionals have a very rigid inner structure, the knowledge of which allows one to build the entire functional derivative from a small part. Based on this analysis, we develop a method for direct construction of integrable Kohn-Sham potentials. As an illustration, we transform the model potential of van Leeuwen and Baerends (which is not a functional derivative) into a semilocal exchange potential that has a parent GGA, yields accurate energies, and is free from the artifacts inherent in existing semilocal potential approximations.

The single and double ionization of the water molecule at large momentum transfer has been studied using a combination of ($e$,$2e$) and ($e$,3–$1e$) spectroscopy, with the binding energy spectrum being measured from 0 to 100 eV. The experiment has been performed in the symmetric noncoplanar geometry at an incident electron energy of 2055 eV. In this way we have achieved a large momentum transfer of 9 a.u. In particular, we present an observation of a relatively intense band at around 58 eV. Symmetry-adapted cluster configuration interaction (SAC-CI) general-R calculations for single ionization indicate that the observed band is at least partly generated by a cluster of satellites with small intensities, which predominantly belong to states possessing ${}^2{A}_1$ symmetry originating from the mixing of the $(2a_1){}^{-1}$ state with two electron processes. Nevertheless, it has been found that the entire spectrum above the lowest double-ionization threshold cannot be understood, even qualitatively, with the SAC-CI calculations. This result suggests that the ($e$,3–$1e$) double-ionization processes have a significant contribution to the observations.

We present a time-independent quantum formalism to describe the dynamics of molecules with permanent electric dipole moments in a two-dimensional confined geometry such as a one-dimensional optical lattice, in the presence of an electric field. Bose versus Fermi statistics and selection rules play a crucial role in the dynamics. As examples, we compare the dynamics of confined fermionic and bosonic polar KRb molecules under different confinements and electric fields. We show how chemical reactions can be suppressed, either by a “statistical suppression” which applies for fermions at small electric fields and confinements, or by a “potential energy suppression,” which applies for both fermions and bosons at high electric fields and confinements. We also explore collisions that transfer molecules from one state of the confining potential to another. Although these collisions can be significant, we show that they do not play a role in the loss of the total number of molecules in the gas.

We consider the ionization of atomic hydrogen by a strong infrared field. By starting from the corresponding time-dependent Schrödinger equation in momentum space, we develop a model in which the kernel of the nonlocal Coulomb potential is replaced by a finite sum of separable potentials. Each separable potential supports one bound state of atomic hydrogen. Here, we consider only the $1s$, $2s$, and $2p$ states. In this way, the full three-dimensional Schrödinger equation reduces to a system of a few coupled one-dimensional linear Volterra integral equations. The objective of this first contribution is to give a detailed account of the model and to validate it in physical situations where the dynamics are well understood.