We have precisely measured the secondary-electron-emission yield (γ) from thin Al, Ag, and Au foils with a thickness of 1 μm on exposure to fully stripped $6\mathrm{MeV}/n$ heavy ions (H, He, C, N, O, Ne, Si, and Ar). The dependence of the forward and backward yields on the projectile nuclear charge (z) showed a proportionality to the square of the effective charge ${(z}_{\mathrm{eff}}^2)$ and an oscillatory behavior with atomic number z; the yields were comparatively low for exposures to ${\mathrm{He}}^{2+}$ and ${\mathrm{Ne}}^{10+}$ beams. The forward enhancement was significant for Al foil (light metal), depending on z; in contrast, it was small for Ag and Au foils (heavy metals). The accuracy of the γ values was evaluated by determination of $z_{\mathrm{eff}}$ (±5%) and the surface reproducibility of the foil (±2–3 %).

We propose a communication protocol exploiting correlations between two events with a definite time ordering: (a) the outcome of a weak measurement on a spin, and (b) the outcome of a subsequent ordinary measurement on the spin. In our protocol, Alice first generates a “code” by performing weak measurements on a sample of N spins. The sample is sent to Bob, who later performs a postselection by measuring the spin along either of two certain directions. The results of the postselection define the “key,” which he then broadcasts publicly. Using both her previously generated code and this key, Alice is able to infer the direction chosen by Bob in the postselection. Alternatively, if Alice broadcasts publicly her code, Bob is able to infer from the code and the key the direction chosen by Alice for her weak measurement. Two possible experimental realizations of the protocols are briefly mentioned.

We have obtained hyperfine-resolved infrared spectra of a ${}^P{Q}_{23}\mathrm{}\left(N\right)\mathrm{}$ branch line in the $v$=2-1 band of the $X{}^3{\Sigma }^{-}$ state of the molecular dication ${\mathrm{D}}^{35}{\mathrm{Cl}}^{2+}.$ Analysis of the hyperfine structure allows us to estimate the magnitude of the Fermi contact interaction for the chlorine nucleus; $b_F$(Cl)=167 (25) MHz.

We calculate exact three-dimensional solutions of Maxwell equations corresponding to strongly focused light beams, and study their interaction with a single atom in free space. We show how the naive picture of the atom as an absorber with a size given by its radiative cross section $\sigma =3\mathrm{}{\lambda }^2/2\mathrm{}\pi$ must be modified. The implications of these results for quantum-information-processing capabilities of trapped atoms are discussed.

The origin of errors in quantum computation implemented by linear optics is studied. The systematic errors of quantum gates, phase relaxation, amplitude dumping, and misreadout are considered as error sources, and the errors which occurred in a four-bit Deutsch-Jozsa algorithm experiment are categorized according to the sources. The increase in the error rate with the expansion of the input size in the Deutsch-Jozsa algorithm is also studied and it was found that the demonstration of 11 qubits using linear optics and a single photon with less than a 20% error rate is achievable by the technique used in the experiment.

We study the effects of a repulsive three-body interaction on a system of trapped ultracold atoms in a Bose-Einstein condensed state. The stationary solutions of the corresponding s-wave nonlinear Schrödinger equation suggest a scenario of first-order liquid-gas phase transition in the condensed state up to a critical strength of the effective three-body force. The time evolution of the condensate with feeding process and three-body recombination losses has a different characteristic pattern. Also, the decay time of the dense (liquid) phase is longer than expected due to strong oscillations of the mean-squared radius.

This is a theory for the effect of localization on the super-Poissonian noise of radiation propagating through an absorbing disordered waveguide. Localization suppresses both the mean photon current $Ī$ and the noise power P, but the Fano factor $P/Ī$ is found to remain unaffected. For strong absorption the Fano factor has the universal value $1+\frac{3}{2}f$ (with f the Bose-Einstein function), regardless of whether the waveguide is long or short compared to the localization length.

Interaction-free measurement schemes with ideal Mach-Zehnder interferometers promised to distinguish absorptive samples with lower average absorption than simple transmission schemes. We show that this is only true for an ensemble of two kinds of samples, where one kind is highly absorptive and the other is highly transmissive. As soon as a third kind of sample with intermediate transmission is introduced, but no phase shift is permitted, the cost of information gain in terms of absorbed particles in the samples is higher in the interferometric scheme. We also investigate the general case of samples with a continuous range of transmission and phase shift values, such that an interferometer’s ability to measure both sample characteristics can be exploited. With an interferometer the number of principally distinguishable samples increases linearly with the number of probe particles, but with a simple transmission setup it increases as the square root. When wishing to distinguish twice as many samples from a continuous sample distribution with an interferometric scheme, the number of absorbed particles per sample only doubles, but it quadruples with a simple transmission scheme.

We derive the optimal curve satisfied by the reduction factors, in the case of a universal disentangling machine that uses only local operations. The impossibility of constructing a better disentangling machine, by using nonlocal operations, is discussed.

We describe the classical and quantum two-dimensional nonlinear dynamics of large blue-detuned evanescent-wave guiding cold atoms in hollow fiber. We show that chaotic dynamics exists for classic dynamics, when the intensity of the beam is periodically modulated. The two-dimensional distributions of atoms in $\mathrm{}(x,y)\mathrm{}$ plane are simulated. We show that the atoms will accumulate on several annular regions when the system enters a regime of global chaos. Our simulation shows that, when the atomic flux is very small, a similar distribution will be obtained if we detect the atomic distribution once each the modulation period and integrate the signals. For quantum dynamics, quantum collapses, and revivals appear. For periodically modulated optical potential, the variance of atomic position will be suppressed compared to the no modulation case. The atomic angular momentum will influence the evolution of wave function in two-dimensional quantum system of hollow fiber.

We have presented a simple treatment to the problem of finding the wave functions for Dirac particles in a time-dependent potential. The treatment is based on the use of Lewis-Riesenfield invariant method [J. Math Phys. 10, 1458 (1969)]. Here we construct a linear time-dependent invariant which allows us to obtain the wave function of the system.

In this work we present an approximate solution of the Schrödinger equation for the two-dimensional three-body Coulomb problem. We study the C3 model that treats the particle’s motion as if it were uncorrelated. We also show the bidimensional ${\Phi }_2$ approximation, based on a recently developed model, which includes some terms of the nonorthogonal Hamiltonian associated with the three-particle correlation. We point out the main similarities and differences with their three-dimensional analogs and verify the correct asymptotic behavior of the wave functions.

We investigate the time evolution of nonlocality for a two-mode squeezed state in a thermal environment. The initial two-mode pure squeezed state is nonlocal with a stronger nonlocality for a larger degree of squeezing. It is found that the larger the degree of initial squeezing, the more rapidly the squeezed state loses its nonlocality. We explain this by the rapid destruction of quantum coherence for the strongly squeezed state.

An analysis of the previously developed coupled propagator theory has been performed in several varieties of second-order perturbation theory. Explicit expressions for elastic and inelastic optical potentials have been derived and compared to the standard form of the (elastic) optical potential for the scattering of nonelectronic projectiles from atoms and molecules. The effects of channel coupling on not only inelastic scattering but also on the elastic channel are particularly transparent in the present approximation. The formalism is suited to describe scattering from degenerate targets. A practical second-order multichannel scheme is briefly presented.

We describe a simple and effective procedure to estimate hydrogen-impact ionization cross sections over the energy range of tens of keV/nucleon to tens of MeV/nucleon. The procedure is valid in the first Born approximation using known or estimated electron-impact cross sections. The original Bates-Griffing relation between the two sets of cross sections is reformulated and a correction factor due to multiple transitions is introduced. Sample calculated ionization cross sections for helium and carbon collisions with hydrogen are presented.

The van der Waals energy of a ground-state atom (or molecule) placed between two metal films is calculated at finite temperature. The attraction between thin metal films and a polarizable object can have half-integer separation dependence. This is in contrast to the usual integer separation dependence, shown for instance in the attraction between an atom and a solid surface. We examine how film thickness, retardation, and temperature influence the interaction. To illustrate the effect of finite thickness of the metal film we calculated the van der Waals energy of ground-state hydrogen and helium atoms, and hydrogen molecules, between thin silver films. We finally, briefly, discuss the possibility to measure this effect.

Combining high-resolution electron spectroscopy with electron-ion coincidence data, we have been able to show the role of bending excitation in the dissociation of ${\mathrm{CO}}_2$ after C $1\overrightarrow{s}{\Pi }_u$ resonant excitation. We demonstrate that the predissociation of the dominating A state created through participator decay is not constant along the resonance profile. The interpretation is based on a preferential excitation of high levels of the bending mode at low-photon-energy side of the resonance, which favors the ${\mathrm{O}}^{+}+\mathrm{CO}$ decay channel.

Ground-state solutions in a dilute gas interacting via contact and magnetic dipole-dipole forces are investigated. To the best of our knowledge, it is the first example of studies of Bose-Einstein condensation in a system with realistic long-range interactions. We find that for the magnetic moment of, e.g., chromium $\left(6\mathrm{}{\mu }_B\right),$ and a typical value of the scattering length, all solutions are stable and only differ in size from condensates without long-range interactions. By lowering the value of the scattering length we find a region of unstable solutions. In the neighborhood of this region, the ground-state wave functions show internal structures that we believe have not been seen before in condensates. Finally, we find an analytic estimate for the characteristic length appearing in these solutions.

Quantum open systems are described in the Markovian limit by master equations in Lindblad form. I argue that common “quantum trajectory” techniques representing continuous measurement schemes, which solve the master equation by unravelling its evolution into stochastic trajectories in Hilbert space, correspond closely to particular sets of decoherent (or consistent) histories. This is illustrated by a simple model of photon counting. An equivalence is shown for these models between standard quantum jumps and the orthogonal jumps of Diósi, which have already been shown to correspond to decoherent histories. This correspondence is compared to simple treatments of trajectories based on repeated or continuous measurements.