Relativistic multireference many-body perturbation theory calculations have been performed on sulfurlike ions as benchmarks for high-accuracy treatment of multiple open-shell ions with as many as six valence shell electrons. Term energies of the 46 excited states arising from the $3s^{2}3p^4$, $3s3p^5$, and $3s^{2}3p^{3}3d$ configurations in ions of the sulfur isoelectronic sequence $(Z=26–32)$ are evaluated to high accuracy. Transition wavelengths associated with electric dipole radiative decays were calculated with an accuracy on the order of $0.01\mathrm{\AA }$ and compared with high-resolution laboratory and solar wavelength measurements to critically evaluate the line identifications.

We propose a cavity QED-based scheme to observe the noncommutativity between the creation and annihilation operators. By conditional measurement after the atom-field interaction in a cavity, it is possible to achieve a photon-added-then-subtracted state and a photon-subtracted-then-added state, which have different statistical properties. This scheme has the advantages of simple analytical results and much higher generation probabilities. We show that the ideal results of one-cycle photon addition and subtraction are approached in the short time limit. We also discuss the possible implementation scheme.

By using the exact four-soliton solutions of the modified Korteweg–de Vries–sine Gordon equation describing the propagation of few-optical-cycle pulses in transparent media with instantaneous cubic nonlinearity, the interaction of two such initially well-separated pulses is studied. The shapes of soliton envelopes, the shifts in the location of envelope maxima, and the corresponding phase shifts are explicitly calculated.

We demonstrate the experimental realization of Bohr-like atoms by applying a pulsed unidirectional field, termed a half-cycle pulse (HCP), to atoms in quasi-two-dimensional near-circular states. This leads to creation of localized wave packets that travel in near-circular orbits and mimic the dynamics of an electron in the original Bohr model of the hydrogen atom. This motion can be followed for several orbital periods before the localization of the wave packet is lost due to dephasing. We show, however, that localization can be recovered by application of further HCPs.

We show that bimodal radio frequency spectra universally arise at intermediate temperatures in models of strongly interacting trapped Fermi gases. The bimodality is independent of superfluidity or pseudogap physics, depending only on the functional form of the equation of state—which is constrained by dimensional analysis at low temperatures and the virial expansion at high temperatures. In addition to these model independent results, we present a simple calculation of the radio frequency line shape of a highly polarized Fermi gas which uses energetic considerations to include final state interactions. While this model only qualitatively captures the line shapes observed in the experiments, it provides a conceptually clean and powerful technique for estimating the energy scales and how they vary with experimental parameters.

Our main goal is to extend and apply the principle of maximum entropy (MaxEnt) to incomplete quantum process estimation tasks. We will define a so-called process entropy function being the von Neumann entropy of the state associated with the quantum process via Choi-Jamiolkowski isomorphism. It will be shown that an arbitrary process estimation experiment can be reformulated in a unified framework and the MaxEnt principle can be consistently exploited. We will argue that the suggested choice for the process entropy satisfies a natural list of properties and it reduces to the state MaxEnt principle if applied to preparator devices.

It has recently been discovered that the optical analog of a gradient echo, in an optically thick material, could form the basis of an optical memory that is both completely efficient and noise-free. Here we present analytical calculations showing that this is the case. There is close analogy between the operation of the memory and an optical system with two beam splitters. We can use this analogy to calculate efficiencies as a function of optical depth for a number of quantum memory schemes based on controlled inhomogeneous broadening. In particular, we show that multiple switching leads to a net 100% retrieval efficiency for the optical gradient echo even in the optically thin case.

We study the dynamical entanglement of vibrations in small molecules by employing algebraic models. We analytically obtain the linear entropy, von Neumann entropy, and the Lyapunov function for the integrable dimer and realistic small molecules for both initial Fock states and coherent states. The contributions of states to the dynamical entropy are also investigated.

We present measurements of oscillator strengths of the $3p^{5}n{d}^{\prime }$ $J=2,3$ autoionizing Rydberg states in argon using two-step laser excitation in conjunction with an optogalvanic detection in a dc discharge cell. The $3p^{5}4p^{\prime }{[3∕2]}_{1,2}$ and ${[1∕2]}_1$ intermediate levels were populated via the $3p^{5}4s{[3∕2]}_2$ metastable state, collisionally populated in the discharge. The photoionization cross section from the $3p^{5}4p^{\prime }{[3∕2]}_{1,2}$ and ${[1∕2]}_1$ intermediate levels has been measured at the $3p^5{}^{2}P_{1∕2}$ ionization threshold as $34\pm 5$, $31\pm 5$, and $28\pm 4\mathrm{Mb}$, respectively, using the saturation technique. The measured absolute cross section values at the $3p^5{}^{2}P_{1∕2}$ threshold have been used to determine the $f$ values for the $4p^{\prime }{[3∕2]}_1\to n{d}^{\prime }{[5∕2]}_2$, $4p^{\prime }{[3∕2]}_2\to n{d}^{\prime }{[5∕2]}_3$, and $4p^{\prime }{[1∕2]}_1\to n{d}^{\prime }{[3∕2]}_2$ transitions. The extracted $f$ values are corrected by incorporating the contribution of the Fano line shape parameters for the autoionizing resonances.

We study the effects of multiple bound states on the probability of tunneling of a homonuclear diatomic molecule incident upon a potential barrier in one dimension. We obtain additional bound states by several means: by varying individual features of the binding potential as well as increasing the mass of the two atoms. We find that the tunneling behavior of a molecule with a large number of bound states $(\sim 30)$ is drastically different from that for a molecule with a small number of states $(\lesssim 5)$. Further, we find that the effect of multiple bound states on the proabability of tunneling is largely dependent upon the separation between the bound-state energies. It is also found that intermediary transitions between many bound states results in significantly larger reductions in the probability of tunneling. Finally, we investigate molecules of different masses and observe common qualitative features. We focus on molecules incident upon a $\delta$ barrier but we also consider Gaussian barriers.

We construct an invisible quantum barrier which represents the phenomenon of quantum reflection using available data on atom-wall and Bose-Einstein-condensate–wall reflection. We use the Abel equation to invert the data. The resulting invisible quantum barrier is double valued in both axes. We study this invisible barrier in the case of atom and Bose-Einstein condensate (BEC) reflection from a solid silicon surface. A time-dependent, one-spatial-dimension Gross-Pitaevskii equation is solved for the BEC case. We found that the BEC behaves very similarly to the single atom except for size effects, which manifest themselves in a maximum in the reflectivity at small distances from the wall. The effect of the atom-atom interaction on the BEC reflection and correspondingly on the invisible barrier is found to be appreciable at low velocities and comparable to the finite-size effect. The trapping of an ultracold atom or BEC between two walls is discussed.

We analyze the dynamics of a paramagnetic, dipolar molecule in a generic “magneto-electrostatic” trap where both magnetic and electric fields may be present. The potential energy that governs the dynamics of the molecules is found using a reduced molecular model that incorporates the main features of the system. We discuss the shape of the trapping potentials for different field geometries, as well as the possibility of nonadiabatic transitions to untrapped states, i.e., the analog of Majorana transitions in a quadrupole magnetic atomic trap. Maximizing the lifetime of molecules in a trap is of great concern in current experiments, and we assess the effect of nonadiabatic transitions on obtainable trap lifetimes.

We investigate the energy levels of heteronuclear alkali-metal dimers in levels correlating with the lowest rotational level of the ground electronic state, which are important in efforts to produce ground-state ultracold molecules. We use density-functional theory to calculate nuclear quadrupole and magnetic coupling constants for KRb and RbCs and explore the hyperfine structure in the presence of electric and magnetic fields. For nonrotating states, the zero-field splittings are dominated by the electron-mediated part of the nuclear spin-spin coupling. They are a few kilohertz for KRb isotopologs and a few tens of kilohertz for RbCs isotopologs.

A method of mid-infrared (ir) $(\lambda \simeq 50\mu \mathrm{m})$ generation at an intraband transition in interband optical $(\lambda \simeq 0.6\mu \mathrm{m})$ semiconductor quantum well (QW) heterolasers is considered. It is based on partial inversion of the intraband transition due to the electron population of its upper level, stimulated by a strong optical field simultaneously generated in the same device. In previous studies of the problem, the inhomogeneous broadening of this transition (i.e., its frequency dependence on the electron energies in the subbands that form it) was not taken into account. As a result, mid-ir generation was possible only under the condition of total (i.e., integrated over electron energies) inversion. In the present work it is shown that the inhomogeneous broadening of the intraband transition allows one to achieve mid-ir generation when it is inverted only in a narrow spectral range containing the interval where its interaction with the mid-ir mode has resonant character. At the same time, total inversion at this transition is absent. This circumstance makes it possible to significantly (by several times in comparison with previous estimates) reduce the threshold pumping current density for the start of mid-ir generation. As a result, this value proves to be in the experimentally achievable domain even at room temperature. This allows one to hope for the practical realization of a pulsed two-color optical and mid-ir laser based on a heterostructure with just one QW, employing simple and cheap injection pumping only, and working without any cooling.

Chip-based cavity quantum electrodynamics (QED) devices consisting of a self-assembled InAs quantum dot (QD) coupled to a high quality factor GaAs microdisk cavity are coherently probed through their optical channel using a fiber taper waveguide. We highlight one particularly important aspect of this all-fiber measurement setup, which is the accuracy to which the optical coupling level and optical losses are known relative to typical free-space excitation techniques. This allows for precise knowledge of the intracavity photon number and measurement of absolute transmitted and reflected signals. Resonant optical spectroscopy of the system under both weak and strong driving conditions are presented, which when compared with a quantum master equation model of the system allows for determination of the coherent coupling rate between QD exciton and optical cavity mode, the different levels of elastic and inelastic dephasing of the exciton state, and the position and orientation of the QD within the cavity. Pump-probe measurements are also performed in which a far off-resonant red-detuned control laser beam is introduced into the cavity. Rather than producing a measurable ac Stark shift in the exciton line of the QD, we find that this control beam induces a saturation of the resonant system response. The broad photoluminescence spectrum resulting from the presence of the control beam in the cavity points to sub-band-gap absorption in the semiconductor, and the resulting free-carrier generation, as the likely source of system saturation.

High-order harmonic generation (HHG) from an excited alkali-metal halide diatomic molecule undergoing electron transfer is considered. A clear signature of electron transfer, a result of a nonadiabatic coupling between the covalent and ionic electronic states, is seen in the HHG spectrum. This work demonstrates the feasibility of HHG probing of simple chemically relevant electronic dynamics, an approach capable of providing spatial and momentum structure regarding the electron transfer process.

We experimentally investigate the high-order harmonic generation in argon gas using a driving laser pulse at a center wavelength of $1240\mathrm{nm}$. High-contrast fine interference fringes could be observed in the harmonic spectra near the propagation axis, which is attributed to the interference between long and short quantum paths. We also systematically examine the variation of the interference fringe pattern with increasing energy of the driving pulse and with different phase-matching conditions.

We propose a scheme for implementing quantum computation with atomic ensembles on an atom chip, where a single qubit is carried by an atomic ensemble instead of a single atom. Two electronic ground states of the atoms are involved, one state with one or no atom is used to represent the qubit and the other state is used to hold the residual atoms. One and two-qubit gates are implemented by internal state transition with laser pulse sequences in the presence of the exciting blockade mechanism. A scalable quantum computer can be realized by one-dimensional or two-dimensional atomic lattices on an atom chip.

This Comment is motivated by some conceptual inconsistencies in the paper by Ronen [Phys. Rev. A 68, 012106 (2003)] and its Addendum [S. Ronen, Phys. Rev. A 68, 064101 (2003)]. While some of the inconsistencies are trivial—such as not distinguishing between anions and cations, and stating that polar molecules are made up of nuclei with positive and negative electric charges—the crucial one concerns the binding energy for an electron in a polar molecule, especially in the context of a confined molecular ion.

Very low-energy electron elastic total and differential cross sections for Hf and Lu atoms exhibit dramatically sharp resonances, whose energy positions are identified with their electron affinities, which are comparable in magnitude with those of Ca and Sr atoms, thus making Hf and Lu atoms suitable candidates for use in the quenching of Rydberg states. The calculation used the recent Regge-pole methodology which embeds the crucial electron correlation effects, with a Thomas-Fermi-type potential incorporating the vital core-polarization interaction. The near-threshold total cross sections for Hf and Lu are contrasted with those of Yb, Ca, and Sr atoms.