Vacuum ultraviolet photoionization of atomic copper is studied within nonrelativistic R-matrix theory. Special care is taken to provide an adequate description of the Cu II target states by means of a configuration interaction method. Using the fact that the R-matrix method allows for an estimate of the relative importance of the $l=0\mathrm{}$ and $l=2\mathrm{}$ channels in the $3\overrightarrow{p}n,\varepsilon l$ photoionization, a complete assignment of the experimental photoabsorption spectrum obtained by Bruhn et al. [J. Phys. B 12, 203 (1979)] is provided. Finally, the coupling of the $3p$ excitations to the dominating spectator decay channels is considered with respect to the resonance line shapes.

Atoms interacting with a standing wave are diffracted into even multiples of photon momentum. We argue that the spreading of the atomic momentum is analogous to the fanning out of Bloch vectors of an ensemble of two-level systems in coherent optics. It is shown that a continuous, time-proportional phase increment of the standing wave reverses the dynamics of the atoms and generates momentum echoes. Monte Carlo wave-function simulations are performed to see how the scheme works for realistic atomic models, taking spontaneous emission into account. Application of the echo formation to lifetime measurements of atoms is proposed.

The quantum state of the electromagnetic field propagating in a nonstationary dielectric can acquire a phase shift that arises from modifications in the quantum fluctuations of the field. The shift could be observed, even for quite weak modifications, as a fringe displacement in an interference experiment.

We construct a Hamiltonian for the generation of arbitrary pure states of the quantized electromagnetic field. The proposition is based upon the fact that a unitary transformation for the generation of number states has already been found. The general unitary transformation here obtained would allow the use of nonlinear interactions for the production of pure states. We discuss the applicability of this method by giving examples of generation of simple superposition states. We also compare our Hamiltonian with the one resulting from the interaction of trapped ions with two laser fields.

The Hardy proof of nonlocality apparently holds in Griffiths’s theory [R. B. Griffiths, Phys. Rev. A 54, 4 (1996)], provided a form of contrafactual “meta-reasoning” about frameworks is allowed.

The argument presented in the preceding Comment is not consistent with the principles of reasoning employed in the consistent histories interpretation of quantum theory, and hence tells us nothing about locality or nonlocality from the perspective of that interpretation.

Recently Joubert [Phys. Rev. A 54, 2479 (1996)] showed that the independent-fermion kinetic-energy kernel has a zero mode. In this Comment we remark that Joubert’s main expression, which leads one to conclude that the contribution arising from the independent-fermion kinetic-energy functional to the local hardness is null, was previously deduced by Garza and Robles [Int. J. Quantum Chem. 49, 159 (1994)].

Pfeffer and co-authors [Phys. Rev. A 55, R2507 (1997)] analyze the anisotropy of photoinduced absorption changes in an assembly of randomly oriented molecules with doubly degenerate transitions, and conclude that the dichroic ratio equals either 8/1 or 4/3. We point out that (i) these numbers, which correspond to the limiting values of a time-dependent observable, have been known for some years, (ii) the time dependence of the dichroic ratio has been measured as well as calculated on various models by several authors, and (iii) the calculation requires consideration of excitation conditions, the directions of the transition moments involved, and the stochastic dynamics of the excited states—an altogether more thorough analysis than is possible on the basis of the authors’ classification of transition types with reference to a simple molecular orbital description.

We discuss a method for distinguishing the four orthogonal Bell states of two entangled particles. Because the scheme relies only on linear optical elements, it should be realizable with current technology. The new feature is that the Bell states must be embedded in a larger Hilbert space. That is, the correlated particles must be entangled in more than one degree of freedom.

We propose a cavity-QED scheme for the controlled generation of sequences of entangled single-photon wave packets. A photon is created inside a cavity via an active medium, such as an atom, and decays into the continuum of radiation modes outside the cavity. Subsequent wave packets generated in this way behave as independent logical quantum bits (qubits). This and the possibility of producing maximally entangled multiqubit states suggest many applications in quantum communication.

We report on the observation of atomic hydrogen $1S-2S$ Doppler-free two-photon Ramsey spectra using two spatially separated interaction regions. We have observed spectra with typical linewidths of 5 kHz at 121 nm, with considerable room for improvements. Our work furthermore represents an important step towards a future hydrogen-atom interferometer for a measurement of the fine-structure constant.

It is shown that, for a photoionization process, in certain cases, a measurement of the integrated cross section ${\sigma }_{\mathrm{nl}},$ and the photoelectron angular-asymmetry parameter ${\beta }_{\mathrm{nl}},$ at an energy for which ${\beta }_{\mathrm{nl}}$ has an extremum, leads to “complete” information about the process, the dipole matrix elements, and their relative phases.

Using a transversely polarized electron beam a relativistic $\mathrm{}(e,2e)\mathrm{}$ experiment has been performed to look for a spin-up–spin-down asymmetry in the electron-impact ionization process caused by the fine-structure effect. An incident energy of 300 keV, coplanar asymmetric kinematics, and the ${2p}_{3/2}$ shell of uranium $\mathrm{}(Z=92\mathrm{})\mathrm{}$ have been used. We found clear evidence for the fine-structure effect in the relativistic regime and a qualitative agreement with theoretical results of the relativistic distorted-wave Born approximation, including a change of sign in the angular distribution of the asymmetry near the Bethe ridge.

A promising ab initio approach to multidimensional quantum scattering by the infinite-order discrete-variable representation is presented. From the rigorous numerical tests on the benchmark collinear ${\mathrm{H}+\mathrm{H}}_2{\to \mathrm{H}}_2+\mathrm{H}$ reaction this approach is proven to yield highly accurate reaction probabilities, substantially reducing computational efforts. Furthermore an expression is presented for direct calculation of the cumulative reaction probability.

Quantum-mechanical scattering calculations of Feshbach resonances arising from van der Waals molecule formation are used to determine vibrational and rotational predissociation lifetimes. A multichannel effective range theory is used to establish the relationship between predissociation and the zero-temperature limit of collisional quenching for resonances lying close to the thresholds for dissociation. The elastic scattering Feshbach resonances may be measurable in ultracold atom-molecule experiments.

We report an experimental study of atomic motion in the Bloch band of a periodic potential. Our system consists of cold sodium atoms in a far detuned standing wave of near resonant light. We prepare the atoms in the lowest motional band, and then impose phase modulation in order to drive interband transitions. We observe Rabi oscillations between the first and second band as a function of modulation intensity and frequency. We also observe damped oscillations of the population as a function of modulation frequency, which are primarily due to a spread in Rabi frequencies over the Bloch band.

The interaction of an atom with a very strong and high-frequency laser is investigated in the context of electron wave-packet stabilization and localization. We employ an exact numerical solution of the Schrödinger equation in two space dimensions, which allows for an arbitrary laser ellipticity. Substantially different degrees of stabilization and electron localization patterns are found for various ellipticities. Circular polarization leads to the highest degree of stabilization.

We present a scheme for the production of circularly polarized multiple high-order harmonic generation (HHG). The proposed experimental setup involves the use of two-color laser fields, consisting of a circularly polarized fundamental laser field and a linearly polarized second-harmonic laser field, in crossed-beam configuration. The feasibility of such a scheme is demonstrated by an ab initio quantal study of the HHG power spectrum of He atoms by means of the time-dependent density-functional theory with optimized effective potential and self-interaction correction recently developed. The theoretical study also provides insights regarding the different mechanisms responsible for the production of HHG in different energy regimes as well as the mechanism for the generation of continuous background radiation.

We show, experimentally and using quantum Monte Carlo simulations, that the quasithermal paramagnetic behavior of cesium atoms in a one-dimensional $\mathrm{lin}\mathrm{\perp }\mathrm{lin}$ optical lattice is characterized by a spin temperature of twice the zero-field kinetic temperature. The magnetization is maximum and almost perfect when the Zeeman shift of the extreme magnetic sublevels approximately equals half the maximum light shift. The lifetime of magnetization and the laser-cooling time constant are found to be clearly distinct, the magnetization decay time amounting to at least three times the cooling time. Using simulations we find that the magnetic-dipole correlation time is approximately proportional to the angular momentum $F$ of the atoms, while cooling and energy correlation time constants are approximately independent of $F.\mathrm{}$ Our results imply that for large $F$ laser cooling within single light-shift potential wells (local cooling) occurs.