The angular distribution of the $L$ x-ray fluorescent lines from Au and U induced by $22.6\text{−}\mathrm{keV}$ x rays from a ${}^{109}\mathrm{Cd}$ has been measured. A Si(Li) detector having a resolution of $160\mathrm{eV}$ at $5.90\mathrm{keV}$ was used to detect these $L$ lines over the angular range of 70°–150°. No strong anisotropy was observed as mentioned by some groups. In the case of Au, a maximum anisotropy of 5% was observed while for U it was within experimental errors (2%). From the angular distribution of the $L1$ line of Au, the alignment parameter was obtained and its value was found to be $0.10\pm 0.14$.

We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of $100\mathrm{pG}∕\sqrt{\mathrm{Hz}}$ (rms) in a $3.5\text{−}\mathrm{cm}$-diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as $25\mathrm{pG}∕\sqrt{\mathrm{Hz}}$ (rms).

We present a self-consistent theory for the thermodynamics of the BCS-BEC crossover in the normal and superfluid phase which is both conserving and gapless. It is based on the variational many-body formalism developed by Luttinger and Ward and by DeDominicis and Martin. Truncating the exact functional for the entropy to that obtained within a ladder approximation, the resulting self-consistent integral equations for the normal and anomalous Green functions are solved numerically for arbitrary coupling. The critical temperature, the equation of state, and the entropy are determined as a function of the dimensionless parameter $1∕k_{F}a$, which controls the crossover from the BCS regime of extended pairs to the BEC regime of tightly bound molecules. The tightly bound pairs turn out to be described by a Popov-type approximation for a dilute, repulsive Bose gas. Even though our approximation does not capture the critical behavior near the continuous superfluid transition, our results provide a consistent picture for the complete crossover thermodynamics which compares well with recent numerical and field-theoretic approaches at the unitarity point.

The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov-Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field $B$.

The circular polarized laser beam of the “magic” wavelength may be used for mixing the ${}^{3}P_1$ state into the long-living metastable state ${}^{3}P_0$, thus enabling the strictly forbidden ${}^{1}S_0\text{−}{}^{3}P_0$ “clock” transition in even isotopes of alkaline-earth-metal-like atoms, without a change of the transition frequency. In odd isotopes the laser beam may adjust to an optimum value the linewidth of the clock transition, originally enabled by the hyperfine mixing. We present a detailed analysis of various factors influencing resolution and uncertainty for an optical frequency standard based on atoms exposed simultaneously to the lattice standing wave and an additional “state-mixing” wave, including estimations of the “magic” wavelengths, Rabi frequencies for the clock and state-mixing transitions, ac Stark shifts for the ground and metastable states of divalent atoms.

Simple examples are presented of Lorentz transformations that entangle the spins and momenta of two particles with positive mass and spin $1∕2$. They apply to indistinguishable particles, produce maximal entanglement from finite Lorentz transformations of states for finite momenta, and describe entanglement of spins produced together with entanglement of momenta. From the entanglements considered, no sum of entanglements is found to be unchanged.

We propose a scheme for continuous-variable quantum cloning of coherent states with phase-conjugate input modes using linear optics. The quantum cloning machine yields $M$ identical optimal clones from $N$ replicas of a coherent state and $N$ replicas of its phase conjugate. This scheme can be straightforwardly implemented with the setups accessible at present since its optical implementation only employs simple linear optical elements and homodyne detection. Compared with the original scheme for continuous-variable quantum cloning with phase-conjugate input modes proposed by Cerf and Iblisdir [Phys. Rev. Lett. 87, 247903 (2001)], which utilized a nondegenerate optical parametric amplifier, our scheme loses the output of phase-conjugate clones and is regarded as irreversible quantum cloning.

Atomic Compton profiles (CPs) are a very important property which provide us information about the momentum distribution of atomic electrons. Therefore, for CPs of heavy atoms, relativistic effects are expected to be important, warranting a relativistic treatment of the problem. In this paper, we present an efficient approach aimed at ab initio calculations of atomic CPs within a Dirac-Hartree-Fock (DHF) formalism, employing kinetically balanced Gaussian basis functions. The approach is used to compute the CPs of noble gases ranging from He to Rn, and the results have been compared to the experimental and other theoretical data, wherever possible. The influence of the quality of the basis set on the calculated CPs has also been systematically investigated.

Soft x-ray lasers operating in the super- $100\mathrm{\AA }$ regime and using grazing incidence pumping methods are now established as efficient sources of radiation in this waveband. The concepts underlying this approach are to separate the ionization and excitation phases of the laser, and to match the pumping density of the latter to the optimal for gain generation. It is therefore of considerable interest to examine whether these ideas can be successfully applied to sub-$100\mathrm{\AA }$ lasers. Three problems arise: first the adverse scaling of ionization with temperature for high atomic number ions, second the strong thermal conduction at these temperatures leads to a large hot zone upstream of the absorption, and third the optimum pumping density is greater than the critical density of $1\mu \mathrm{m}$ wavelength, solid state pump lasers. Using analytic models and simulation we identify a strategy to overcome these problems using a pre-pulse of a mixed harmonic and fundamental radiation of Nd-glass laser radiation followed by the main pumping pulse of the fundamental normally incident. Due to the large upstream thermal zone and the high ionization temperature, we find that the energy required in the pre-pulse is much ($\sim 3$ times) larger than that in the main, and that the energy needed consequently scales rapidly with the atomic number and therefore decreasing x-ray wavelength. Systems generating output energies of a few tens of $\mu \mathrm{J}$ are examined at wavelengths between 50 and $70\mathrm{\AA }$.

We show that the pulse matching phenomenon can be obtained in the general multilevel system with electromagnetically induced transparency. For this we find a different way to create tightly localized stationary pulses by using counterpropagating pump fields. The present process is a spatial compression of excitation so that it allows us to shape and further intensify the localized stationary pulses, without using standing waves of pump fields or spatially modulated pump fields.

We investigate the power of quantum systems for the simulation of Hamiltonian time evolutions on a cubic lattice under the constraint of translational invariance. Given a set of translationally invariant local Hamiltonians and short-range interactions we determine time evolutions which can and those that cannot be simulated. Whereas for general spin systems no finite universal set of generating interactions is shown to exist, universality turns out to be generic for quadratic bosonic and fermionic nearest-neighbor interactions when supplemented by all translationally invariant on-site Hamiltonians.

We study a one-dimensional Ising model with a magnetic field and show that tilting the field induces a transition to quantum chaos. We explore the stationary states of this Hamiltonian to show the intimate connection between entanglement and avoided crossings. In general, entanglement gets exchanged between the states undergoing an avoided crossing with an overall enhancement of multipartite entanglement at the closest point of approach, simultaneously accompanied by diminishing two-body entanglement as measured by concurrence. We find that both for stationary as well as nonstationary states, nonintegrability leads to a destruction of two-body correlations and distributes entanglement more globally.

We describe the use of a special interaction symmetry for the robust generation of the totally symmetric superposition state or entangled state of an $N$-state system. The required symmetry of the Hamiltonian is that of a circulant matrix. Such a matrix has the important property that its eigenstates are independent of the matrix elements as long as the circulant symmetry is maintained. One of the eigenvectors is the target superposition. By inducing a slow evolution of the Hamiltonian into the circulant form, adiabatic following will generate the desired superposition out of a convenient initial state such as a product state. The creation process is robust: it is insensitive to details of the interaction as long as the final Hamiltonian has the required symmetry. We illustrate the procedure with a simple example: a ring of quantum wells that permit interwell tunneling, into which a single atom is placed. By carrying out adiabatic evolution the state vector approaches an equal distribution of probability amplitudes in each well.

The effects of rovibrational temperature on dissociative electron attachment to hydrogen bromide has been investigated from the experimental and theoretical point of view. Theoretical calculations based on the nonlocal resonance model predict a strong temperature effect on the ${\mathrm{Br}}^{-}$ fragment ion yield due to population of higher vibrational and rotational states. A crossed beam experimental setup consisting of a temperature controlled effusive molecular beam and a trochoidal electron monochromator has been used to confirm this prediction. The high degree of agreement between experiment and theory indicates the validity of the theoretical model and its underlying physical picture.

The second-order Faddeev-Watson-Lovelace approximation in a modified form is applied to charge transfer from hydrogenlike target atoms by a fully stripped energetic projectile ion. The state-to-state, $nlm\to n^{\prime }{l}^{\prime }{m}^{\prime }$, partial transition amplitudes are calculated analytically. The method is specifically applied to the collision of protons with hydrogen atoms, where differential cross sections of different transitions are calculated for incident energies of 2.8 and $5.0\mathrm{MeV}$. It is shown that the Thomas peak is present in all transition cross sections. The partial cross sections are then summed and compared with the available forward-angle experimental data, showing good agreement.

The Schwinger multichannel method is applied to study the low-energy electron-impact excitation of molecular nitrogen. The scattering amplitudes are obtained within the minimal orbital basis for single configuration interactions (MOBSCI) level of approximation, for impact energies from near threshold up to $30\mathrm{eV}$. Through the use of the MOBSCI strategy we have performed a close-coupling calculation for up to nine states, including the ground state and all singlet and triplet states resulting from the ${\pi }_u\to {\pi }_g$ transitions. Integral and differential cross sections for the $X{}^1\Sigma _g^{+}\to A{}^3\Sigma _u^{+}$, $W{}^3\Delta _u$, $B^{\prime }{}^3\Sigma _u^{-}$, $a^{\prime }{}^1\Sigma _u^{-}$, and $w{}^1\Delta _u$ electronic transitions are presented and compared with available experimental data and also with other theoretical results.

We show how efficient control can be exerted on molecular dissociation by adiabatic shaping of an intense, single laser pulse in a very simplified way, involving a few parameters (e.g., peak amplitude, carrier-wave, and modulation phases and frequencies). The strategy takes advantage of an appropriate combination of basic multiphoton mechanisms: bond softening (BS), vibrational trapping (VT), and dynamical dissociation quenching (DDQ). The resulting stabilization enhancement with respect to dissociation may increase up to a factor of 5, while simultaneously inhibiting the BS mechanism and reenforcing the VT mechanism, using DDQ. The photodissociation of $\mathrm{H}_2{}^{+}$ submitted to a uv-visible field modulated by an IR periodic envelope, on which the consequences of a DDQ-type mechanism has recently experimentally been checked, is taken as an illustrative example.

A four-level atom interferometer comprised of three excited states and one ground state with trichromatic fields coupled between them is investigated using Zeeman sublevels of ${}^{3}P_1$ and ${}^{1}S_0$ states of a calcium atom. A theoretical description of the interaction of four-level atoms with trichromatic laser fields is presented and compared with the experimental results of the interference fringes which are generated by the three excited states.

We discuss a $(1+1)$-dimensional Galilean invariant model recently introduced in connection with ultracold quantum gases. After showing its relation to a nonrelativistic $(2+1)$ Chern-Simons matter system, we identify the generators of the supersymmetry and its relation with the existence of self-dual equations.