An alternative approach for calculation of the electron excitation probability accompanying inner-shell vacancy production is presented. The change in the central potential of the atom due to the creation of an inner-shell vacancy is estimated and the electron transition probability between two shells is calculated treating this change as the perturbation. The calculated results are in agreement with the shake-up probabilities using the wave-function overlap and the experimental values.

A detailed quantum kinetic master equation is developed that couples the kinetics of a trapped condensate to the vapor of noncondensed particles. This generalizes previous work that treated the vapor as being undepleted.

Generalized oscillator strengths for the Na $3s-3p$ transition have been investigated using the spin-polarized technique of the random phase approximation with exchange (RPAE) and the Hartree-Fock approximation, focusing our attention on the position of the minimum. Intershell correlations are found to influence the position of the minimum significantly, but hardly that of the maximum. The RPAE calculation predicts the positions of the minimum and maximum at momentum transfer, K values of 1.258 and 1.61 a.u., respectively. The former value is within the range of values $K=1.0\mathrm{}–1.67\mathrm{a}.\mathrm{u}.\mathrm{}$ extracted by us from experimental measurements. We recommend a careful experimental search for the position of the minimum around the predicted value for confirmation.

A time-dependent non-Hermitian close-coupling method is developed for describing the interplay of decaying atomic dressed states in short laser pulses. This interplay accounts for a variety of phenomena. It is shown, in particular, that the probability that the atom is excited off-resonance is modulated by Stueckelberg oscillations, that the ionization yield may be reduced by dynamical coupling with a resonant and rapidly decaying dressed state, and that adiabatic stabilization of circular states subsists down to very short pulse durations.

We propose and demonstrate a scheme for a blue-detuned optical dipole trap for cold atoms which consists of a single, rapidly rotating laser beam. We characterize a parameter range in which the optical potential can be accurately described by a quasistatic time-averaged potential. The trap is loaded with $>{10}^6$ Rb atoms, and is then compressed adiabatically by a factor of 350 to a final density of $5\times {10}^{13}$ ${\mathrm{cm}}^{-3}.$ $\mathrm{A}\sim 4$ times adiabatic increase in the peak phase-space density of the trapped atoms is obtained due to the change in the shape of the trap potential. The two-body elastic and inelastic collision rates of atoms in the compressed trap are determined.

A parentage projection method is used to study the detailed ${}^2{P}^o$ resonances of Li between the ${\mathrm{Li}}^{+}1s2p{}^{1}P$ and $1s3s{}^{3}S$ thresholds. This method is simple and is independent of the basis function used. Seventeen resonances are uncovered in the photoionization spectra between 71 and 74 eV. The energy, width, and structures are presented. In this energy region, two high-resolution experimental spectra exist due to different calibration procedures. Our predicted photoionization cross section profile agrees closely with one of the spectra to the level of a few meV and disagrees with the other spectrum.

It is shown that the photoelectron-angular distribution asymmetry parameter $\beta ,$ arising from $\mathrm{ns}$ photoionization in open-shell atoms, is quite a bit more sensitive to interchannel coupling than the integrated cross section. An example of $4s$ photoionization of atomic Sc is presented. It is demonstrated that this effect can occur throughout the periodic system.

We present a general time-dependent approach for efficient and accurate treatment of high-resolution spectrocopy and quantum dynamics. The procedure is applied to an ab initio time-dependent study of three-dimensional Rydberg H atoms in crossed magnetic and electric fields with spectral accuracy. Good agreement with the high-resolution experimental photoabsorption spectrum is obtained line by line, including a regime well above the Stark saddle point. We have further explored the physical origin of several unexplored perplexing phenomena in the higher-energy regime observed in the experiment.

A nonrelativistic R-matrix theory for many-electron systems is formulated in the language of integral operators. A relationship between the operator and matrix formulations is provided. Six variational principles related to the subject are presented. The Rayleigh-Ritz linear trial functions are used in these principles, yielding second-order variational estimates of eigenvalues, elements, and reciprocals of elements of the R matrix and its inverse. Following the ideas of Hinze and Hamacher [J. Chem. Phys. 92, 4372 (1990)], a multiconfiguration Hartree-Fock approach to the R-matrix method is proposed.

A nonequilibrium approach to the dynamics and statistics of the condensate of an ideal N-atom Bose gas cooling via interaction with a thermal reservoir using the canonical ensemble is developed. We derive simple analytical expressions for the canonical partition function and equilibrium distribution of the number of atoms in the ground state of a trap under different approximations, and compare them with exact numerical results. The N-particle constraint associated with the canonical ensemble is usually a burden. In the words of Kittel, “in the investigation of the Bose-Einstein…laws it is very inconvenient to impose the restriction that the number of particles in the subsystem shall be held constant.” But in the present approach, based on the analogy between a second-order phase transition and laser threshold behavior, the N-particle constraint makes the problem easier. We emphasize that the present work provides another example of a case in which equilibrium (detailed balance) solutions to nonequilibrium equations of motion provide a useful supplementary approach to conventional statistical mechanics. We also discuss some dynamical and mesoscopic aspects of Bose-Einstein condensation. The conclusion is that the present analytical (but approximate) results, based on a nonequilibrium approach, are in excellent agreement with exact (but numerical) results. The present analysis has much in common with the quantum theory of the laser.

Typical quantum computing schemes require transformations (gates) to be targeted at specific elements (qubits). In many physical systems, direct targeting is difficult to achieve; an alternative is to encode local gates into globally applied transformations. Here we demonstrate the minimum physical requirements for such an approach: a one-dimensional array composed of two alternating “types” of two-state system. Each system need be sensitive only to the net state of its nearest neighbors, i.e. the number in state $“\uparrow ”$ minus the number in $“\downarrow .”$ Additionally, we show that all such arrays can perform quite general parallel operations. A broad range of physical systems and interactions is suitable: we highlight two examples.

A study of the photoexited Ge $K{\beta }^{\prime \prime \prime }$ x-ray satellites from onset to saturation using inelastic x-ray scattering is presented. The assignment of the satellites to $\left[1s3d\right]$ and $\left[1s3p\right]$ excitation channels is confirmed by determination of their different threshold energies and energy positions on the high-energy tail of the $K{\beta }_2$ fluorescence line. Direct measurement of the variation of the satellite intensities with increasing excitation energy exhibits a long saturation range to the sudden limit and yields indication for the opening of a $\left[1s3s\right]$ excitation channel to the $\left[1s3p\right]$ satellite. In this work we separate the contributions of the double-electron excitations to the absorption spectrum and show pure satellite spectra for possible application in experiment based extended x-ray-absorption fine-structure background subtraction taking into account the full properties of the solid state.

The charge-state evolution of highly charged ions transmitted through microcapillaries is studied theoretically by a classical trajectory Monte Carlo simulation. The interaction of highly charged ions with the internal surface of the capillary is treated within the framework of dielectric response theory. We analyze the distance of closest approach and the angular distributions of the highly charged ions at the exit of the microcapillary. We find the charge-state fraction of transmitted ${\mathrm{N}}^{6+}$ projectiles, in good agreement with first measurements. Moreover, our calculations indicate that grazing collisions with the microcapillary surface hold the promise of direct observation of charge transfer and hollow-atom formation at a large distance from the surface.

The measuring process is an external intervention in the dynamics of a quantum system. It involves a unitary interaction of that system with a measuring apparatus, a further interaction of both with an unknown environment causing decoherence, and then the deletion of a subsystem. This description of the measuring process is a substantial generalization of current models in quantum measurement theory. In particular, no ancilla is needed. The final result is represented by a completely positive map of the quantum state $\rho$ (possibly with a change of the dimensions of $\rho ).\mathrm{}$ A continuous limit of the above process leads to Lindblad’s equation for the quantum-dynamical semigroup [Commun. Math. Phys. $48,$ 119 (1976)].

If several interventions performed on a quantum system are localized in mutually spacelike regions, they will be recorded as a sequence of “quantum jumps” in one Lorentz frame, and as a different sequence of jumps in another Lorentz frame. Conditions are specified that must be obeyed by the various operators involved in the calculations, so that these two different sequences lead to the same observable results. These conditions are similar to the equal-time commutation relations in quantum field theory. They are sufficient to prevent superluminal signaling. (The derivation of these results does not require most of the contents of the preceding article [Peres, Phys. Rev. A 61, 022116 (2000)]. What is needed is briefly summarized here, so that the present article is essentially self-contained.)

A realization of the concept of “crossing state” invoked, but not implemented, by Wigner, allows advancement in two important aspects of the formalization of the time of arrival in quantum mechanics: (i) For free motion, we find that the limitations described by Aharonov et al. in Phys. Rev. A 57, 4130 (1998) for the time-of-arrival uncertainty at low energies for certain measurement models are in fact already present in the intrinsic time-of-arrival distribution of Kijowski ${\Pi }_K;$ (ii) we have also found a covariant generalization of this distribution for arbitrary potentials and positions.

Two approaches to extend Hardy’s proof of nonlocality without inequalities to maximally entangled states of bipartite two-level systems are shown to fail. On one hand, it is shown that the proof of Wu and co-workers [Phys. Rev. A 53, R1927 (1996)] uses an effective state which is not maximally entangled. On the other hand, it is demonstrated that Hardy’s proof cannot be generalized by the replacement of one of the four von Neumann measurements involved in the original proof by a generalized measurement to unambiguously discriminate between nonorthogonal states.

Canonically conjugated observables such as position and momentum and phase and number are found to play a threefold role in quantum teleportation. First, the common eigenstate of two commuting canonical observables like phase difference and number sum provides the quantum channel between two systems. Second, a similar pair of canonical observables from another two systems is measured in the Bell-operator measurements. Finally, two translations generated by the canonically conjugated observables of a single system constitute the local unitary operation to recover the unknown state. In addition, the necessary and sufficient condition is presented for a reliable quantum teleportation of finite-level systems.

When a subset of particles in an entangled state is measured, the state of the subset of unmeasured particles is determined by the outcome of the measurement. This first measurement may be thought of as a state preparation for the remaining particles. This type of measurement is important in quantum computing, quantum information theory, and in the preparation of entangled states such as the Greenberger-Horne–Zeilinger state. In this paper, we examine how the duration of the first measurement effects the state of the unmeasured subsystem. We discuss the case for which the particles are photons, but the theory is sufficiently general that it can be converted to a discussion of any type of particle. The state of the unmeasured subsytem will be a pure or mixed state depending on the nature of the measurement. In the case of quantum teleportation we show that there is an eigenvalue equation which must be satisfied for accurate teleportation. This equation provides a limitation to the states that can be accurately teleported.