Kinetic energy distributions of alkali-metal atoms (sodium and rubidium) desorbed from poly-dimethylsiloxane coated glasses via visible $\left(532\text{nm}\right)$ and near-infrared $\left(1064\text{nm}\right)$ laser irradiation are determined. In each case the time-of-flight spectra show a single desorption peak. In the case of sodium the mean kinetic energy of the desorbing atoms depends on the photon energy and linearly on the laser fluence. Evanescent-wave desorption measurements show that the origin of the desorbed atoms is within the bulk of the thin organic film. The results are discussed in terms of electronic excitation and resonant heating, providing values of barrier heights for desorption from PDMS. The observed small barrier heights explain the weak light intensity necessary for light-induced atomic desorption from such systems.

Energy distributions of ions emitted from argon clusters (up to $12800\text{atoms}∕\text{cluster}$) Coulomb-exploded with an intense femtosecond laser have been experimentally studied. Under the laser intensity of $2\times {10}^{16}\mathrm{\text{W}}∕{\text{cm}}^2$, the ions of $>15\text{keV}$ are anisotropically emitted, while those lower than $15\text{keV}$ tend to be isotropic. The argon ions of charge state up to ${\mathrm{Ar}}^{14+}$ were generated, and their high charge state is more than expected by the barrier suppression ionization model. The yield and maximum energy of ${\mathrm{Ar}}^{8+}\text{–}{\mathrm{Ar}}^{14+}$ ions depend on laser polarization direction, while those of ${\mathrm{Ar}}^{+}\text{–}{\mathrm{Ar}}^{7+}$ are much less sensitive to the laser polarization. The present results suggests that high-charge-state and anisotropically emitted ions are produced by impact ionization of electrons that are produced by optical field ionization with the intense laser.

We have laser collimated a gallium atomic beam in one dimension using the linear-perpendicular-linear polarization gradient technique. Operating on the cycling $4p^2{P}_{3∕2}(F=3)\to 4d^2{D}_{5∕2}(F=4)$ transition at $294.45\text{nm}$, the full angular divergence of the atomic beam was reduced to $0.3\text{mrad}$, corresponding to a transverse velocity of $\pm 11\text{cm}∕\mathrm{s}$, about one-half the Doppler cooling limit. The dependence of the cooling efficiency on the laser detuning and power was investigated. Optical pumping of the atoms out of the $4p^2{P}_{3∕2}(F=3)$ state by the cooling laser was observed. Repumping schemes were investigated and found to successfully repopulate the cooled $F=3$ hyperfine state.

Using state-selective field ionization, the state distributions of Rydberg atoms in cold Rydberg gases are measured for various initially excited Rydberg levels, populations, and evolution times. We provide direct experimental evidence for $l$-changing collisions that we previously observed indirectly [S. K. Dutta, D. Feldbaum, A. Walz-Flannigan, J. R. Guest, and G. Raithel, Phys. Rev. Lett. 86, 3993 (2001)]. We also observe $n$-mixing and find that its effects are largely in agreement with recent theoretical work on $n$-changing collisions between electrons and Rydberg atoms, thus enabling an estimation of the electron temperature. Unexpectedly large populations of atoms are found in states with principal quantum numbers much lower than that of the initially excited atoms. We explain this observation by collisions between high-$l$ Rydberg atoms, which are highly polar and can collide due to static electric-dipole forces between them.

A decelerated beam of neutral ammonia molecules is injected into an electrostatic storage ring. Electrostatic lenses are used to map the emittance of the decelerator onto the acceptance of the ring. The tangential velocity spread of the package of molecules in the ring is set to less than $1\mathrm{m}∕\mathrm{s}$. The package of molecules can be observed for more than 50 distinct round trips, corresponding to $40\mathrm{m}$ in circular orbit and almost $0.5\mathrm{s}$ storage time, sufficiently long for a first investigation of its transversal motion in the ring.

With saturation and probing by circularly polarized fields, quantum coherence effects are investigated for the cycling transition $F_e=0\leftrightarrow F_g=1$, which is subject to a linearly polarized field and a magnetic field. The saturation field is applied to the case of maximum coherence between the drive Rabi frequency and magnetic field, corresponding to the electromagnetically induced absorption (EIA) with negative dispersion found by Gu et al. For a small saturation Rabi frequency, holes are burned in two Autler-Towns peaks outside two symmetric electromagnetically induced transparency windows due to the two-photon resonance. However, when the saturation Rabi frequency is comparable with the drive Rabi frequency, holes caused by the coherent population oscillation appear in the EIA spectrum. Finally, when the saturation Rabi frequency is large enough, several emission peaks are observed due to the Mollow absorption effects. Furthermore, the dispersion at the pump-probe detuning center is kept negative with an increase in saturation field, which is a precursor of superluminal light propagation.

A nonperturbative numerical evaluation of the one-photon electron self-energy for the $3S$ and $4S$ states with charge numbers $Z=1$ to 5 is described. The numerical results are in agreement with known terms in the expansion of the self-energy in powers of $Z\alpha$.

The theory of ${\mathrm{Ne}}^{+}$ and ${\mathrm{Ne}}^{2+}$ ion formation with due account of sequential, nonsequential and inelastic tunneling is compared with the experimental data [D. N. Fittinghoff et al., Phys. Rev. A 49, 2174 (1994)].

We present a scheme to realize the basic two-qubit logic gates such as the quantum phase gate and the controlled-NOT gate using a detuned optical cavity interacting with a three-level Raman system. We discuss the role of Stark shifts, which are as important as the terms leading to the two-photon transition. The operation of the proposed logic gates involves metastable states of the atom and hence is not affected by spontaneous emission. These ideas can be extended to produce multiparticle entanglement.

Relativistic multireference many-body perturbation theory is generalized to calculate the energies of highly excited levels in multivalence-electron ions of iron group elements responsible for soft-x-ray emission lines. Term energies of the highly excited $n=4$ states arising from the $3s^{2}3p4l\left(l=0–3\right)$ and $3s3p^{2}4l\left(\mathrm{l}=0–3\right)$ configurations in $\mathrm{Fe}\text{XIII}$ are computed to high accuracy. Theoretical electric dipole transition probabilities and wavelengths of the transitions to low-lying $n=3$ levels are compared with solar and laboratory lines to identify hitherto unidentified $\text{and}∕\text{or}$ poorly characterized extreme ultraviolet and soft-x-ray spectral lines. $E1$, $E2$, and $M1$ decay rates and lifetimes of lower excited levels of the $n=3$ manifold are evaluated as a benchmark for future experiments.

In this work we investigate the general properties and the ground state of an asymmetrical dilute gas of cold fermionic atoms, formed by two particle species having different densities. We have shown in a recent paper, that a mixed phase composed of normal and superfluid components is the energetically favored ground state of such a cold fermionic system. Here we extend the analysis and verify that in fact, the mixed phase is the preferred ground state of an asymmetrical superfluid in various situations. We predict that the mixed phase can serve as a way of detecting superfluidity and estimating the magnitude of the gap parameter in asymmetrical fermionic systems.

We discuss the quasi one-dimensional (1-D) scattering of two counterpropagating, dark-state polaritons (DSPs), each containing a single excitation. DSPs are formed from photons in media with electromagnetically induced transparency and are associated with ultraslow group velocities. State-dependent elastic collisions of atoms at the same lattice site lead to a nonlinear interaction. It is shown that the scattering process in a deep optical lattice filled by cold atoms generates a large and homogeneous conditional phase shift between two individual polaritons. The latter has potential applications for a photonic phase gate. The quasi-1-D scattering problem is solved analytically and the influence of degrading processes such as dephasing due to collisions with ground-state atoms is discussed.

The surface impedance approach is discussed in connection with the precise calculation of the Casimir force between metallic plates. It allows us to take into account the nonlocal connection between the current density and electric field inside of metals. In general, a material has to be described by two impedances $Z_s(\omega ,q)$ and $Z_p(\omega ,q)$ corresponding to two different polarization states. In contrast with the approximate Leontovich impedance they depend not only on frequency $\omega$ but also on the wave vector along the plate $q$. In this paper only the nonlocal effects happening at frequencies $\omega <{\omega }_p$ (plasma frequency) are analyzed. We refer to all of them as the anomalous skin effect. The impedances are calculated for the propagating and evanescent fields in the Boltzmann approximation. It is found that $Z_p$ significantly deviates from the local impedance as a result of the Thomas-Fermi screening. The nonlocal correction to the Casimir force is calculated at zero temperature. This correction is small but observable at small separations between bodies. The same theory can be used to find more significant nonlocal contribution at $\omega \sim {\omega }_p$ due to the plasmon excitation.

We investigate the irreversibility of entanglement distillation for a symmetric $\left(d+1\right)$-parameter family of mixed bipartite quantum states acting on Hilbert spaces of arbitrary dimension $d\times d$. We prove that in this family the entanglement cost is generically strictly larger than the distillable entanglement, so that the set of states for which the distillation process is asymptotically reversible is of measure zero. This remains true even if the distillation process is catalytically assisted by pure-state entanglement and every operation is allowed, which preserves the positivity of the partial transpose. It is shown that reversibility occurs only in cases where the state is a tagged mixture. The reversible cases are shown to be completely characterized by minimal uncertainty vectors for entropic uncertainty relations.

In quantum-process tomography it is possible to express the experimenter’s prior information as a sequence of quantum operations, i.e., trace-preserving completely positive maps. In analogy to de Finetti’s concept of exchangeability for probability distributions, we give a definition of exchangeability for sequences of quantum operations. We then state and prove a representation theorem for such exchangeable sequences. The theorem leads to a simple characterization of admissible priors for quantum process tomography and solves to a Bayesian’s satisfaction the problem of an unknown quantum operation.

The selection rule which forbids $J=1\leftrightarrow 0$ two-photon decay when the energies of the two photons are equal is shown to apply only when the multipolarities of the two photons are the same (i.e., $2E1$, $2M1$, etc.) and does not generally apply to mixed multipolarity amplitudes such as $E1M2$. A calculation of the two-photon decay rate for He-like ions in the $2{}^{3}S_1$ state including both $2E1$ and $E1M2$ two-photon decay amplitudes is presented. It shows a significant contribution for the case of equal-energy photons. The ratio of the $E1M2$ contribution to the $2E1$ contribution is found to be surprisingly large. For example, it is 0.27 for two-photon decay of the $2{}^{3}S_1$state in He-like uranium.

We present detailed comparisons between the two quantal approaches—hyperspherical close-coupling and common-reaction-coordinate close-coupling methods—on an exemplary case of ${\text{He}}^{2+}+\mathrm{H}\left(1s\right)$ collisions at center-of-mass energy from $20\text{eV}$ up to $1.6\text{keV}$. It is shown that the partial-wave charge-transfer cross sections from the two approaches agree very well at low energy below $200\text{eV}$ down to $30\text{eV}$. This good agreement is a strong indication of the validity of both methods. The small difference at very low energies and the convergence with respect to the number of channels in both approaches at higher energies are also discussed.

A detailed theory of four-wave mixing (FWM) at a gas-solid interface is developed. Geometry of excitation, where two electromagnetic waves propagate perpendicularly to the interface and the third one is evanescent traveling along it, is considered. Assuming that the evanescent wave penetration depth into the gas is much less than the mean free path of gas molecules, it is shown that FWM spectroscopy allows to distinguish between the contributions from gas molecules moving to the surface, desorbed from it and directly scattered into the gas. It is concluded that by scanning the wave frequencies across the molecular transitions it is possible to determine the parameters of the scattering kernel for direct gas-surface scattering and the velocity-dependent sticking probability. A method based on this principle could open opportunity for studying adsorption, desorption and gas-surface scattering dynamics not only under thermodynamically nonequilibrium conditions but as well as in an equilibrium gas phase.

We propose a scheme to achieve multiparty entanglement with perfectly efficient, ultraslow, multichannel pairwise four-wave mixing (FWM). A cold atomic medium is illuminated with an $N$-mode continuous-wave (cw) control laser to produce coherent mixtures of excited states. An ultraslowly propagating, single-photon quantum probe field completes multichannel, pairwise FWM, creating a depth dependent entanglement of $N$ Fock states. We show explicitly that this scheme can be utilized to realize an $N$-party entangled state of ultraslowly propagating quantized fields. In particular, we give the explicit analytical expression of a three-party W-state propagating at an ultraslow group velocity, and the numerical results of a multiparty W state of $2M+1$ Fock states.

We demonstrate that a cancellation of absorption occurs on resonance for two (or any even number of) coupled optical resonators, due to mode splitting and classical destructive interference, particularly when the resonator finesse is large and the loss in the resonator farthest from the excitation waveguide is small. The linewidth and group velocity of a collection of such coupled-resonator structures may be decreased by using larger resonators of equal size, by using larger resonators of unequal size where the optical path length of the larger resonator is an integer multiple of that of the smaller one, or by using a larger number of resonators per structure. We explore the analogy between these effects and electromagnetically-induced transparency in an atomic system.