We have carried out an accurate determination of the quadrupole moment of the deuteron nucleus. The evaluation of the constant is achieved by combining high accuracy Born-Oppenheimer calculations of the electric field gradient at the nucleus in the ${\mathrm{H}}_2$ molecule with spectroscopic measurements of the quadrupolar splitting in ${\mathrm{D}}_2$ and HD. The derived value is $Q=0.285783(30$) fm${}^2$.

We investigate high-lying doubly excited nonautoionizing states of helium with total angular momentum $L=1,2,\dots ,9$ with the help of a configuration interaction approach. We provide highly precise nonrelativistic energies of these states and discuss the properties of the wave functions with respect to the particle exchange operator.

A spectral approach of configuration interaction type is used to evaluate energies and widths for a wide range of singlet and triplet $P^{\mathrm{e}}$ resonance states of helium up to the eighth single ionization threshold. While the present data are in excellent agreement with existing theoretical results (below the $N=3$–$5$ ionization threshold) obtained within an explicitly correlated approach, there are substantial differences with the energies, the widths, and the number of resonances obtained with the stabilization method.

We report differential cross sections for electron impact excitation of the $a\hspace{0.5em}{}^1{\Pi }_g$, $C\hspace{0.5em}{}^3{\Pi }_u$, $E\hspace{0.5em}{}^3{\Sigma }_g^{+}$, $a^{″}\hspace{0.5em}{}^1{\Sigma }_g^{+}$, $b\hspace{0.5em}{}^1{\Pi }_u$, $c_3\hspace{0.5em}{}^1{\Pi }_u$, $o_3\hspace{0.5em}{}^1{\Pi }_u$, $b^{\prime }\hspace{0.5em}{}^1{\Sigma }_u^{+}$, $c_4^{\prime }\hspace{0.5em}{}^1{\Sigma }_u^{+}$, $G\hspace{0.5em}{}^3{\Pi }_u$, and $F\hspace{0.5em}{}^3{\Pi }_u$ electronic states in ${\mathrm{N}}_2$. The incident electron energies are 20, 30, and 40 eV, while the scattered electron angles are ${10}^{°}$ and ${20}^{°}$. These kinematic conditions were specifically targeted in order to try and shed new light on the worrying discrepancies that exist in the literature for the $a\hspace{0.5em}{}^1{\Pi }_g$, $C\hspace{0.5em}{}^3{\Pi }_u$, $E\hspace{0.5em}{}^3{\Sigma }_g^{+}$, and $a^{″}\hspace{0.5em}{}^1{\Sigma }_g^{+}$ cross sections, and in general the present measurements confirm that those from the more recent results of the University of California, Fullerton, and the Jet Propulsion Laboratory [M. A. Khakoo, P. V. Johnson, I. Ozkay, P. Yan, S. Trajmar, and I. Kanik, Phys. Rev. A 71, 062703 (2005); C. P. Malone, P. V. Johnson, I. Kanik, B. Ajdari, and M. A. Khakoo, Phys. Rev. A 79, 032704 (2009)] are reliable. In addition, we provide a rigorous cross-check for the remaining seven electronic states, where the only recent comprehensive study is from Khakoo and colleagues [Phys. Rev. A 77, 012704 (2008)]. Here, however, some of those cross sections are confirmed and others are not, suggesting that further work is still needed.

The ionization of xenon Rydberg atoms at metallic surfaces is examined. The data show that, when the effects of stray electric “patch” fields present on the surface are taken into account, ionization is well described by a simple over-the-barrier model. The patch fields are determined from direct measurements of the potential variations across the target surfaces using Kelvin probe force microscopy. Monte Carlo techniques are used to model the atom-surface interaction. The results confirm the important role that patch fields can play during Rydberg atom-surface interactions and suggest that such interactions can provide a sensitive probe of stray fields at surfaces.

In this article, we study the thermalizability of a system consisting of two atoms in a circular, transversely harmonic waveguide in the multimode regime. While showing some signatures of quantum-chaotic behavior, the system fails to reach a thermal equilibrium in a relaxation from an initial state, even when the interaction between the atoms is infinitely strong. We relate this phenomenon to the previously addressed unattainability of a complete quantum chaos in the Šeba billiard [P. Šeba, Phys. Rev. Lett. 64, 1855 (1990)], and we conjecture the absence of a complete thermalization to be a generic property of integrable quantum systems perturbed by a nonintegrable but well-localized perturbation.

We use spatial light modulators (SLMs) to measure correlations between arbitrary superpositions of orbital angular momentum (OAM) states generated by spontaneous parametric down-conversion. Our technique allows us to fully access a two-dimensional OAM subspace described by a Bloch sphere, within the higher-dimensional OAM Hilbert space. We quantify the entanglement through violations of a Bell-type inequality for pairs of modal superpositions that lie on equatorial, polar, and arbitrary great circles of the Bloch sphere. Our work shows that SLMs can be used to measure arbitrary spatial states with a fidelity sufficient for appropriate quantum information processing systems.

The cooperative Lamb shift (CLS) is hard to measure because in samples much larger than a resonant wavelength it is much smaller, for an initially prepared resonantly phased state, than the cooperative decay rate (CDR). We show, however, that if the phasing of the initial state is detuned so that the spatial wave vector is $k_1\cong k_0\pm O(\frac{1}{R})$ (where $k_0={\omega }_0/c$ is the resonant frequency), the CLS grows to “giant” magnitudes making it comparable to the CDR. Moreover, for certain controlled values of detuning, the initial CDR becomes small so that the dynamical Lamb shift (DLS) can be measured over a considerable period of time.

We present a method to encode a dressed qubit into the product state of an electron spin localized in a quantum dot and its surrounding nuclear spins via a dressing transformation. In this scheme, the hyperfine coupling and a portion of a nuclear dipole-dipole interaction become logic gates, while they are the sources of decoherence in electron-spin qubit proposals. We discuss errors and corrections for the dressed qubits. Interestingly, the effective Hamiltonian of nuclear spins is equivalent to a pairing Hamiltonian, which provides the microscopic mechanism to protect dressed qubits against decoherence.

We study the polarization state of high-order harmonics produced by linearly polarized light interacting with two-center molecules. By generating high-harmonic “polarization maps” from Radon transformations of excited electronic wave functions, we show that the polarization of the harmonic radiation can be linked to the geometry of the molecular orbital. While in the Radon transformation the plane-wave approximation for the rescattered electron is implicitly assumed, numerical solutions of the two-dimensional time-dependent Schr$\stackrel{\mathrm{··}}{\mathrm{o}}$dinger equation, in which this approximation is not made, confirm the validity of this topological connection. We also find that measuring two orthogonal amplitude components of the harmonics provides a method for quantum tomography that substantially improves the quality of reconstructed molecular states.

Differential Stark shift compensation for ground-state ${}^{87}\mathrm{Rb}$ atoms trapped in an elliptically polarized optical lattice and “magic” magnetic field was recently proposed and demonstrated experimentally by N. Lundblad et al. [e-print arXiv:0912.1528] and analyzed theoretically by A. Derevianko [e-print arXiv:0912.3233]. Here we demonstrate enhanced hyperfine coherence times using the magic field technique. We observe coherent light storage with a $0.32$-s lifetime in an atomic Rb gas confined in a one-dimensional optical lattice and magnetic field.

The phase shift and visibility of fringes in the Ramsey atom interferometer composed of the $|F=1$,$m_F=0\rangle$ and $|F=2$,$m_F=0\rangle$ states were examined systematically for rapid half-rotation of the magnetic field. It was verified that the phase shifts by $\pi$ rad in the adiabatic regime, but it does not shift from the original one in the nonadiabatic regime. These results support Robbins and Berry’s claim [J. M. Robbins and M. V. Berry, J. Phys. A 27, L435 (1994)]. The fact that the interference fringes disappear in the intermediate regime and reappear in the nonadiabatic regime can be explained by the Majorana transition caused by a rapid reverse of the magnetic field.

We propose a scalable implementation of Grover’s quantum search algorithm in a trapped-ion quantum information processor. The system is initialized in an entangled Dicke state by using adiabatic techniques. The inversion-about-average and oracle operators take the form of single off-resonant laser pulses. This is made possible by utilizing the physical symmetries of the trapped-ion linear crystal. The physical realization of the algorithm represents a dramatic simplification: each logical iteration (oracle and inversion about average) requires only two physical interaction steps, in contrast to the large number of concatenated gates required by previous approaches. This not only facilitates the implementation but also increases the overall fidelity of the algorithm.

We derive a new bound on the minimum-error probability for ambiguous discrimination and compare the new bound with six other bounds in the literature. Specifically, the main technical contributions are as follows. (1) We obtain a general lower bound on the minimum-error probability for ambiguous discrimination among arbitrary $m$ mixed quantum states with given prior probabilities. We further analyze how this lower bound is attainable by presenting a necessary and sufficient condition related to it. (2) We compare this new lower bound with six other bounds in the literature, in detail. We show that this new bound improves the previous one in the literature and in the equiprobable case; the new bound also improves another one. Moreover, we give an example to show that this new bound is the tightest one for some cases.

We study dipolar relaxation in both ultracold thermal and Bose-condensed Cr atom gases. We show three different ways to control dipolar relaxation, making use of either a static magnetic field, an oscillatory magnetic field, or an optical lattice to reduce the dimensionality of the gas from three-dimensional (3D) to two-dimensional (2D). Although dipolar relaxation generally increases as a function of a static magnetic-field intensity, we find a range of nonzero magnetic-field intensities where dipolar relaxation is strongly reduced. We use this resonant reduction to accurately determine the $S=6$ scattering length of Cr atoms: $a_6=103\pm 4a_0$. We compare this new measurement to another new determination of $a_6$, which we perform by analyzing the precise spectroscopy of a Feshbach resonance in $d$-wave collisions, yielding $a_6=102.5\pm 0.4a_0$. These two measurements provide, by far, the most precise determination of $a_6$ to date. We then show that, although dipolar interactions are long-range interactions, dipolar relaxation only involves the incoming partial wave $l=0$ for large enough magnetic-field intensities, which has interesting consequences on the stability of dipolar Fermi gases. We then study ultracold Cr gases in a one-dimensional (1D) optical lattice resulting in a collection of independent 2D gases. We show that dipolar relaxation is modified when the atoms collide in reduced dimensionality at low magnetic-field intensities, and that the corresponding dipolar relaxation rate parameter is reduced by a factor up to $7$ compared to the 3D case. Finally, we study dipolar relaxation in the presence of rf oscillating magnetic fields, and we show that both the output channel energy and the transition amplitude can be controlled by means of the rf frequency and Rabi frequency.

The effect of the electron’s anomalous magnetic moment on the relativistic electronic dressing for the process of electron-hydrogen atom elastic collisions is investigated. We consider a laser field with circular polarization and various electric field strengths. The Dirac-Volkov states taking into account this anomaly are used to describe the process in the first order of perturbation theory. The correlation between the terms coming from this anomaly and the electric field strength gives rise to the strong dependence of the spinor part of the differential cross section (DCS) with respect to these terms. A detailed study has been devoted to the nonrelativistic regime as well as the moderate relativistic regime. Some aspects of this dependence as well as the dynamical behavior of the DCS in the relativistic regime have been addressed.

The Dirac-based $B$-spline $R$-matrix method is used to investigate the photoionization of atomic potassium from the $4s$ ground and $4p$, $5s$-$7s$, $3d$-$5d$ excited states. The effect of the core polarization by the outer electron is included through the polarized pseudostates. Besides the dipole core polarization, we also found a noticeable influence of the quadrupole core polarization. We obtained excellent agreement with experiment for cross sections of the $4s$ photoionization, including accurate description of the near-threshold Cooper-Seaton minimum. We also obtained close agreement with experiment for the $4p$ photoionization, but there are unexpectedly large discrepancies with available experimental data for photoionization of the $5d$ and $7s$ excited states.

We demonstrate a two-element oven and Zeeman slower that produce simultaneous and overlapped slow beams of rubidium and lithium. The slower uses a three-stage design with a long, low-acceleration middle stage for decelerating rubidium situated between two short, high-acceleration stages for aggressive deceleration of lithium. This design is appropriate for producing high fluxes of atoms with a large mass ratio in a simple, robust setup.

We theoretically and numerically analyze x-ray scattering from asymmetric-top molecules three-dimensionally aligned using elliptically polarized laser light. A rigid-rotor model is assumed. The principal axes of the polarizability tensor are assumed to coincide with the principal axes of the moment of inertia tensor. Several symmetries in the Hamiltonian are identified and exploited to enhance the efficiency of solving the time-dependent Schrödinger equation for each rotational state initially populated in a thermal ensemble. Using a phase-retrieval algorithm, the feasibility of structure reconstruction from a quasiadiabatically aligned sample is illustrated for the organic molecule naphthalene. The spatial resolution achievable strongly depends on the laser parameters, the initial rotational temperature, and the x-ray pulse duration. We demonstrate that for a laser peak intensity of 5 TW/cm${}^2$, a laser pulse duration of 100 ps, a rotational temperature of 10 mK, and an x-ray pulse duration of 1 ps, the molecular structure may be probed at a resolution of 1 Å.