We present an analytic model to calculate the atomic scattering length near a Feshbach resonance from data on the molecular binding energy. Our approach considers finite-range square-well potentials and can be applied near broad, narrow, or even overlapping Feshbach resonances. We test our model on ${\mathrm{Cs}}_2$ Feshbach molecules. We measure the binding energy using magnetic-field modulation spectroscopy in a range where one broad and two narrow Feshbach resonances overlap. From the data we accurately determine the Cs atomic scattering length and the positions and widths of two particular resonances.

Superconducting electrical circuits can be used to study the physics of cavity quantum electrodynamics (QED) in new regimes, therefore realizing circuit QED. For quantum-information processing and quantum optics, an interesting regime of circuit QED is the dispersive regime, where the detuning between the qubit transition frequency and the resonator frequency is much larger than the interaction strength. In this paper, we investigate how nonlinear corrections to the dispersive regime affect the measurement process. We find that in the presence of pure qubit dephasing, photon population of the resonator used for the measurement of the qubit act as an effective heat bath, inducing incoherent relaxation and excitation of the qubit. Measurement thus induces both dephasing and mixing of the qubit, something that can reduce the quantum nondemolition aspect of the readout. Using quantum trajectory theory, we show that this heat bath can induce quantum jumps in the qubit state. Nonlinear effects can also reduce the achievable signal-to-noise ratio of a homodyne measurement of the voltage.

We show that configurations exist in which the correlation functions and the degree of violation of Bell-type inequalities in the relativistic Einstein-Podolsky-Rosen (EPR) experiment have local extrema for some values of the velocities of the EPR particles. Moreover, this strange behavior can be observed for both discussed relativistic spin operators and for spin-$1∕2$ as well as spin-1 particles.

We reexamine the Salecker-Wigner-Peres clock formalism and show that it can be directly applied to the phenomenon of tunneling. Then we apply this formalism to the determination of the tunneling time of a nonrelativistic wave packet, sharply concentrated around a tunneling energy, incident on a symmetric double-barrier potential. In order to deepen the discussion about the generalized Hartman effect, we consider the case in which the clock runs only when the particle can be found inside the region between the barriers and show that, whenever the probability to find the particle in this region is non-negligible, the corresponding time (which in this case turns out to be a dwell time) increases with barrier spacing.

High-resolution measurements of the photoabsorption spectra of silver in the $4d$-subshell excitation region are reported using synchrotron radiation as the background source of the continuum. The spectra were recorded in the first order of a $3\text{−}\mathrm{m}$ spectrograph equipped with a $6000\text{−}\text{lines}∕\mathrm{mm}$ holographic grating at a dispersion of $0.5\mathrm{nm}∕\mathrm{mm}$ and using photographic detection. Rydberg series have been observed converging to four conspicuous limits built on the $4d^{9}5s$ parent ion configuration $4d^{10}5s{}^{2}S_{1∕2}\to 4d^{9}5s({}^{3}D_{3,2,1},{}^{1}D_2)$ $np$ and $nf$ $(J=1)$. The high-resolution data reveal extended Rydberg series, accurate term energies, quantum defects, and widths of the autoionizing resonances. The resonance energies and widths of the leading members of the series have been determined using multichannel quantum defect theory.

We show that the convergence behavior of the many-body numerical diagonalization scheme for strongly interacting bosons in a trap can be significantly improved by the Lee-Suzuki method adapted from nuclear physics: One can construct an effective interaction that acts in a space much smaller than the original Hilbert space. In particular for short-ranged forces and strong correlations, the method offers a good estimate of the energy and the excitation spectrum, at a computational cost several orders of magnitude smaller than that required by the standard method.

Spectra of $K\alpha$ x rays emitted from Ar gas at atmospheric pressure under bombardment by $10\mathrm{MeV}∕\mathrm{amu}$ heavy ions (atomic number 6–79) were measured in high resolution using a curved crystal spectrometer. Values of the apparent average fraction of $L$ vacancies at the time of $K\alpha$ x-ray emission $\left(p_L^x\right)$ were determined from the observed $K\alpha$ satellite and hypersatellite intensity distributions. A systematic comparison of the $p_L^x$ values for the monatomic gas Ar with those obtained previously for a variety of solid targets provided a quantitative assessment of the role interatomic transitions play in the $L$-vacancy transfer process that occurs prior to $K$ x-ray decay.

We present a combined experimental and theoretical investigation of the fully differential cross section for electron-impact ionization of neon and xenon. The experiments were performed under coplanar asymmetric kinematics, at intermediate incident electron energies, and for a range of scattered electron detection angles. The experimental results are compared with three calculations: a convergent close-coupling calculation, a distorted-wave Born approximation (DWBA) calculation with inclusion of the Gamow factor, and a hybrid $\mathrm{DWBA}+R$-matrix calculation. The comparison between the experimental and theoretical results highlights the importance of the description of postcollision interaction, and the results exhibit interesting orbital-dependent differences.

We present an experimental study that maps the transformation of nuclear quadrupole resonances (NQRs) from the pure nuclear quadrupole regime to the quadrupole-perturbed Zeeman regime. The transformation presents an interesting quantum-mechanical problem since the quantization axis changes from being aligned along the axis of the electric-field gradient tensor to being aligned along the magnetic field. The large nuclear quadrupole shifts present in our system enable us to study this regime with relatively high resolution. We achieve large nuclear quadrupole shifts for $I=3∕2$ ${}^{131}\mathrm{Xe}$ by using a cube-shaped $1{\mathrm{mm}}^3$ vapor cell with walls of different materials. The enhancement of the NQR shift from the cell wall materials is an observation that opens up an additional adjustable parameter to tune and enhance the nuclear quadrupole interactions in vapor cells. As a confirmation that the interesting and complex spectra that we observe are indeed expected, we compare our data to numerical calculations and find excellent agreement.

The coherence time, and thus sensitivity, of trapped-atom interferometers that use nondegenerate gases are limited by the collisions between the atoms. An analytic model that describes the effects of collisions between atoms in an interferometer is developed. It is then applied to an interferometer using a harmonically trapped nondegenerate atomic gas that is manipulated with a single set of standing wave laser pulses. The model is used to find the optimal operating conditions of the interferometer and direct Monte Carlo simulation of the interferometer is used to verify the analytic model.

We develop a systematic formalism to study the propagation of a guided probe light field along a nanofiber embedded in a cold atomic gas. We derive a general axial propagation equation for the amplitude of the photon flux of the guided light, which allows us to take into account the complexity of the guided-field vector structure and the evanescent-wave nature of the guided-field transverse profile. We use our formalism to explore the possibility of slowing down of the guided light via the process of electromagnetically induced transparency. We show that, despite the effects of the spatially varying detuning, caused by the van der Waals potential, and the spatially varying atom-field coupling, caused by the evanescent-wave nature of the guided mode in the transverse plane, the group velocity of the guided light can be substantially reduced due to the steep dispersion of the atomic gas in the condition of electromagnetically induced transparency.

We investigate the nonlocal property of the fractional statistics in Kitaev’s toric code model. To this end, we construct the Greenberger-Horne-Zeilinger paradox which builds a direct conflict between the statistics and local realism. It turns out that the fractional statistics in the model is purely a quantum effect and independent of any classical theory. We also discuss a feasible experimental scheme using anyonic interferometry to test this contradiction.

We propose a scheme to generate an Abelian gauge field in an atomic gas using two crossed laser beams. If the internal atomic state follows adiabatically the eigenstates of the atom-laser interaction, Berry’s phase gives rise to a vector potential that can nucleate vortices in a Bose gas. The present scheme operates even for a large detuning with respect to the atomic resonance, making it applicable to alkali-metal atoms without significant heating due to spontaneous emission. We test the validity of the adiabatic approximation by integrating the set of coupled Gross-Pitaevskii equations associated with the various internal atomic states, and we show that the steady state of the interacting gas indeed exhibits a vortex lattice, as expected from the adiabatic gauge field.

We report on experiments studying the transport properties of an atomic Bose-Einstein condensate in an optical lattice of spatial period $\lambda ∕2n$, where $n$ is an integer, realized with the dispersion of multiphoton Raman transitions. We observe Bloch oscillations, as a clear effect of quantum transport, in a subwavelength-scale periodicity lattice. An unusually large tunneling coupling between lattice sites is evident from the measured effective mass. Future prospects of the different lattice structures are expected in the search for new quantum phases in tailored lattice structures up to quantum computing in optical nanopotentials.

We examine the evolution of paraxial beams carrying intrinsic spin and orbital angular momenta (AM) in gradient-index media. A parabolic-type equation is derived which describes the beam diffraction in curvilinear coordinates accompanying the central ray. The center of gravity of the beam experiences transverse AM-dependent deflections—the spin and orbital Hall effects. The spin Hall effect generates a transverse translation of the beam as a whole, in precise agreement with recent geometrical optics predictions. At the same time, the orbital Hall effect is significantly affected by the diffraction in the inhomogeneous medium and is accompanied by changes in the intrinsic orbital AM and deformations of the beam.

Samples with a few hundred atoms within a few $\mu \mathrm{m}$ sized regions of space are large enough to provide efficient cooperative absorption and emission of light, and small enough to ensure strong dipole-dipole interactions when atoms are excited into high-lying Rydberg states. Based on a recently proposed collective encoding scheme, we propose to build few-qubit quantum registers in such samples. The registers can receive and emit quantum information in the form of single photons, and they can employ entanglement pumping protocols to perform ideally in networks for scalable quantum computing and long distance quantum communication.

We have examined loading of ${}^{85}\mathrm{Rb}$ atoms into a shallow far-off-resonance trap (FORT) from an optical molasses stage following a magneto-optical trap (MOT) stage and compared it to loading from a MOT stage only. Substantially more atoms could be loaded into the FORT using an optical molasses. To determine why this was the case, we measured the rate of atoms loaded into the FORT and the losses from the FORT during both loading processes over a range of detunings and hyperfine pump powers. We found that the losses induced during MOT loading were essentially the same as the losses induced during molasses loading and decreased with increased red detuning; however, we found that the differences in load rate caused an optical molasses to optimize at a greater detuning, improving the number of atoms we could trap by a factor of 2 over that of optimal loading from a MOT.

We theoretically study multiphoton ionization through the triplet states of Mg by linearly polarized and circularly polarized fs laser pulses. After the construction of the atomic basis using the frozen-core Hartree-Fock potential as well as the model potential approaches for both singlet and triplet series which show rather good agreements with the existing data in terms of state energies and dipole matrix elements, we solve time-dependent Schrödinger equations with $3s3p$ ${}^{3}P_1$ as an initial state, and calculate the total ionization yield and photoelectron energy spectra.

On the basis of the phase diagram of the uniform system, we calculate the density profiles of a trapped polarized Fermi gas at zero temperature using the local density approximation. By varying the overall polarization and the interaction strength, we analyze the appearance of a discontinuity in the profile, signaling a first-order phase transition from a superfluid inner core to a normal outer shell. The local population imbalance between the two components and the size of the various regions of the cloud corresponding to different phases are also discussed. The calculated profiles are quantitatively compared with the ones recently measured by Shin et al. [Phys. Rev. Lett. 101, 070404 (2008)].