We have used the Ramsey method of separated oscillatory fields to probe the dipole-dipole interaction of Rb $nsnp$ pair states of $33\le n\le 41$. In the Ramsey method dipole-dipole broadening in an inhomogeneous sample is manifested as a decrease in the fringe contrast with increasing density. An attractive feature of this approach compared to conventional line broadening is that the effect of the dipole-dipole interaction can be seen near the center of the Ramsey interference pattern, where the signal is large, as opposed to in the wings, where it is small. We observe dipole-dipole broadening which scales as $n^4$, in agreement with the calculated broadening. In addition, the Ramsey method points to the existence of $nsn{p}_{1/2}$ states which have no dipole-dipole shift.

Experimental results of Stokes parameters and electron-impact coherence parameters for excitation of $4{}^1{P}_1$ state of zinc atoms are presented. The electron-photon coincidence method in the coherence-analysis version was applied to obtain data for scattering angles in the range from $5^{\circ }$ to 40${}^{\circ }$ for incident electron energy 100 eV. The experimental results are presented together with convergent-close-coupling-method and relativistic-distorted-wave-approximation theoretical predictions.

State-selective electron capture cross sections and projectile scattering-angle differential cross sections for single-electron capture in collisions of protons with He at energies ranging from 50 to 100 keV have been experimentally investigated by means of a reaction microscope. It is shown that for single-electron capture the ground-state transfer is the dominant reaction channel, and excited-state transfer has relative small contributions to the cross sections. The transfer-excitation process has a minor contribution to the total cross sections. As the projectile energy increases, ground-state transfer remains dominant, but the relative contributions of the excited-state transfers become more important. The minor contribution of transfer excitation remains almost unchanged. Furthermore, it was found that for single transfer the present results are in good agreement with independent electron model predictions in the energy regime considered. For transfer excitation, however, there are obvious discrepancies between our measurements and theoretical results. We concluded that the electron-electron-correlation effects may play a role at least in transfer excitation in collisions of protons with He in the energy range considered.

We present the experimental realization of a compressible blue-detuned crossed dipole trap for cold atoms allowing for fast dynamical compression ($\sim$5–10 ms) of $5\times {10}^7$ rubidium atoms up to densities of $\sim$${10}^{13}{\text{cm}}^{-3}$. The dipole trap consists of two intersecting tubes of blue-detuned laser light. These tubes are formed using a single, rapidly rotating laser beam which, for sufficiently fast rotation frequencies, can be accurately described by a quasistatic potential. The atomic cloud is compressed by dynamically reducing the trap volume, leading to densities close to the Ioffe-Regel criterion for light localization.

By exploring the spin-orbit-coupled rotating pseudo-spin-1/2 Bose-Einstein condensates with the stochastic projected Gross-Pitaevskii equations, we prove the existence of the circular-hyperbolic skyrmion, which possesses two extreme values of $S_z$. The nonequal intraspecies interactions and interspecies interactions cause the two components to be wholly disproportionate when the system reaches the equilibrium state. The circular-hyperbolic skyrmion results from the vortex-dipole structure. For the miscible condensates, the increase of spin-orbit coupling enhances the creation of the circular-hyperbolic skyrmion, and makes them link one after another locally. In particular, the circular-hyperbolic skyrmion even can form a chain when the spin-orbit coupling is only in one direction. For the immiscible condensates, the hyperbolic skyrmion occurs at the center, while the circular-hyperbolic skyrmion occurs at the outskirts of the condensates. The increase of the spin-orbit coupling restricts the creation of the hyperbolic skyrmion and enhances the creation of the circular-hyperbolic skyrmion.

Upon increasing the strength of Rashba spin-orbit coupling $\lambda$, induced by a synthetic non-Abelian gauge field, a system of fermions at a finite density $\rho \approx k_F^3$ evolves to a BEC-like state [J. P. Vyasanakere, S. Zhang, and V. B. Shenoy, Phys. Rev. B 84, 014512 (2011)], even in the presence of a weak attractive interaction described by a scattering length $a_s$. The BEC obtained at large spin-orbit coupling ($\lambda \gg k_F$) is a condensate of novel bosonic bound pairs of fermions (called “rashbons”) whose properties are determined solely by the gauge field. Here we investigate the collective excitations of such superfluids by constructing a Gaussian theory using functional integral methods. We show that there is an emergent Galilean invariance at large $\lambda$, and the phase stiffness is determined by the rashbon density and mass, consistent with Leggett's theorem. We further demonstrate that the rashbon BEC (RBEC) is a superfluid of anisotropic rashbons interacting via a contact interaction characterized by a rashbon-rashbon scattering length $a_R$. We show that $a_R$ goes as ${\lambda }^{-1}$ and is essentially independent of the interaction between the fermions as long as it is nonzero. Analytical results are reported for high-symmetry gauge fields.

A detailed vibrationally and rotationally resolved study for the fragmentation dynamics of the hydrogen molecular ion (${{\text{H}}_2}^{+}$) under intense short laser pulses is presented. Our theoretical nonadiabatic quantum molecular dynamics approach allows us to dynamically include all degrees of freedom for ionization also. We find that in general rotation enhances ionization compared to that in rotationally frozen molecules, with a weaker effect on highly vibrationally excited states. We identify the alignment time of one-quarter of the rotational period as the parameter which decides the dynamical relevance of rotation. Our analysis explains the dominance of dissociation over ionization observed experimentally and also clarifies why dimensionally reduced calculations predict a dominance of ionization.

We analyze nonlinear effects associated with the spatiotemporal propagation of few-cycle optical pulses in nonlinear dispersive media, including nonlinearity-induced self-phase modulation, generation of higher harmonics, and the effects of diffraction. First, we discuss the nonlinear equations governing the spatiotemporal propagation of short pulses in dispersive and diffractive nonlinear media and demonstrate a link between the field equation and the cubic nonlinear Schrödinger equation employed for describing the evolution of the pulse envelope. Then, for several different regimes of competitive scales, we study the self-action effects of few-cycle pulses and describe, both analytically and numerically, the pulse self-modulation and self-focusing, including the transformation of the spectral density and harmonic generation in the cases of weak and strong dispersion. Finally, we analyze the effect of the beam diffraction on self-action of the Gaussian few-cycle pulses.

We propose a cooling scheme for the V-type three-level atom tightly confined in a harmonic trap. Two excited levels are coupled to the ground state by a quadrupole transition with a small dissipation rate and a dipole transition with a large dissipation rate, respectively. The quadrupole transition is strongly driven by a running-wave laser 1, which acts as the cooling channel in the Lamb-Dicke regime. The dipole one is weakly driven by another running-wave laser 2 as the auxiliary transition. Ground-state cooling with a large rate can be achieved through the appropriate choice of Rabi frequency for laser 1 and the detuning of the auxiliary transition.

Expansion of a degenerate Bose gas released from a pancakelike trap is numerically simulated under the assumption of separation of the motion in the plane of the loose initial trapping and the motion in the direction of the initial tight trapping. The initial conditions for the phase fluctuations are generated using the extension to the two-dimensional case of the description of the phase noise by the Ornstein-Uhlenbeck stochastic process. The numerical simulations, taking into account both the finite size of the two-dimensional system and the atomic interactions, which cannot be neglected on the early stage of expansion, did not reproduce the scaling law for the peaks in the density fluctuation spectra experimentally observed by Choi, Seo, Kwon, and Shin [Phys. Rev. Lett. 109, 125301 (2012)]. The latter experimental results may thus require an explanation beyond our current assumptions.

We show how a dressed lattice scheme can provide control over certain types of noise for atomic quantum gases in the lowest band of an optical lattice, removing the effects of global lattice amplitude noise to first order for particular choices of the dressing field parameters. We investigate the nonequilibrium many-body dynamics of bosons and fermions induced by noise away from this parameter regime, and show how the same technique can reduce spatial disorder in projected lattice potentials.

We demonstrate that the thermal Casimir-Polder forces on molecules near a conducting surface whose transition wavelengths are comparable to the molecule-surface separation are dependent on the ambient temperature and molecular polarization and they can even be changed from attractive to repulsive by varying the temperature across a threshold value for anisotropically polarizable molecules. Remarkably, this attractive-to-repulsive transition may be realized at room temperature. Let us note that the predicted repulsion is essentially a nonequilibrium effect since the force we calculated on a ground-state (or an excited-stated) molecule actually contains the contribution of the absorption (or emission) of thermal photons.

Patch potentials arising from the polycrystalline structure of material samples may contribute significantly to measured signals in Casimir force experiments. Most of these experiments are performed in the sphere-plane geometry; yet, up to now all analysis of patch effects has been taken into account using the proximity force approximation which, in essence, treats the sphere as a plane. In this paper we present the exact solution for the electrostatic patch interaction energy in the sphere-plane geometry and derive exact analytical formulas for the electrostatic patch force and minimizing potential. We perform numerical simulations to analyze the distance dependence of the minimizing potential as a function of patch size, and we quantify the sphere-plane patch force for a particular patch layout. Once the patch potentials on both surfaces are measured by dedicated experiments our formulas can be used to exactly quantify the sphere-plane patch force in the particular experimental situation.

The behavior of strong-field ionization rates of neutral atoms in the vicinity of multiphoton ionization thresholds is analyzed using formal collision theory. Our approach, which accounts nonperturbatively for effects of an intense laser field, shows that the ionization rates have a nearly constant behavior below and above each multiphoton threshold and that between such thresholds there are an apparently finite number of rapid oscillations due to resonances with laser-field-modified Rydberg states. This pattern is typical for any atomic target, as we illustrate specifically for hydrogen and neon atoms. The flat behavior of the ionization yield near multiphoton thresholds gives the appearance of an energy shift of the ionization thresholds, which have been postulated in a number of recent studies concerning diverse aspects of above-threshold ionization and high-harmonic generation of atoms. The flat behaviors of the rates near threshold exhibit only a rather weak dependence on the laser-field intensity. Other aspects of the near-threshold behavior of ionization rates and their dependence on the laser-field parameters are also discussed.

We develop the two-electron attosecond streak camera under realistic conditions using a quasiclassical model. We assume extreme ultraviolet (XUV) attosecond pulses with a full width at half maximum (FWHM) of 24 attoseconds, centered at 120 eV and a streaking infrared laser field of 1600 nm, and intensity of $1.8\times {10}^{12}$ W/cm${}^2$. The proposed method is shown to be capable of time resolving two-electron collisions in double ionization.

We study the dynamics and the resulting state after relaxation in a quasidisordered integrable lattice system after a sudden quench. Specifically, we consider hard-core bosons in an isolated one-dimensional geometry in the presence of a quasiperiodic potential whose strength is abruptly changed to take the system out of equilibrium. In the delocalized regime, we find that the relaxation dynamics of one-body observables, such as the density, the momentum distribution function, and the occupation of the natural orbitals, follow, to a good approximation, power laws. In that regime, we also show that the observables after relaxation can be described by the generalized Gibbs ensemble, while such a description fails for the momentum distribution and the natural orbital occupations in the presence of localization. At the critical point, the relaxation dynamics is found to be slower than in the delocalized phase.

The Maxwell fish eye lens has previously been reported as being capable of the much sought after phenomenon of subwavelength imaging. The inclusion of a drain in this system is considered crucial to the imaging ability, although its role is the topic of much debate. This paper provides a numerical investigation into a practical implementation of a drain in such systems, and analyzes the strong frequency dependence of both the Maxwell fish eye lens and an alternative, the Miñano lens. The imaging capability of these types of lens is questioned, and it is supported by simulations involving various configurations of drain arrays. Finally, a discussion of the near-field and evanescent wave contribution is given.

A photon wave mechanical theory describing evanescent electromagnetic fields, as these appear in $p$-polarized total internal reflection from a flat dielectric-to-vacuum interface, is presented. In this first-quantized field theory, the Lorenz gauge four-potential relates to the wave functions of the transverse (T), longitudinal (L), and scalar (S) photons. For a homogeneous medium, the source domain (rim zone) of the L photons is shown to coincide with the longitudinal vector-field parts of an electron sheet current density located at the interface. The identical rim zones of the T and L photons exhibit one-dimensional (1D) exponential confinement with a spatial decay constant equal to the magnitude of the incident field's wave vector along the interface plane. The S-photon 1D localization is complete (has $\delta$-function character). Dynamical equations are established for the L- and S-photon variables in the wave-vector–time domain. These Hamiltonian-like equations are easily upgraded to the second-quantized level. The link to the wave mechanics of near-field photons is made. When extended to the quantum electrodynamic level, the present theory is an alternative to the pioneering Carniglia-Mandel (CM) triplet-photon description. It is argued that our theory provides one with an improved physical understanding of the basic role of T photons in evanescent fields. Wave mechanics of evanescent fields give additional insight in the T-photon localizability problem. The particular difficulties arising for $s$-polarized external fields are addressed referring to the rim zone of quantum wells.

We theoretically analyze the light scattering of an optomechanical cavity which strongly interacts with a single two-level system and couples simultaneously to a mechanical oscillator by radiation forces. The analysis is based on the assumptions that the system is driven at low intensity, and that the mechanical interaction is sufficiently weak, permitting a perturbative treatment. We find quantum interference in the scattering paths, which allows one to suppress the Stokes component of the scattered light. This effect can be exploited to reduce the motional energy of the mechanical oscillator.

A general theory of optical forces on moving bodies is here developed in terms of generalized $4\times 4$ transfer and scattering matrices. Results are presented for a planar dielectric of arbitrary refractive index placed in an otherwise empty space and moving parallel and perpendicular to the slab-vacuum interface. In both regimes of motion the resulting force comprises lateral and normal velocity-dependent components, which may depend in a subtle way on the Doppler effect and $s$-$p$-polarization mixing. For lateral displacements in particular, polarization mixing, which is here interpreted as an effective magnetoelectric effect due to the reduced symmetry induced by the motion of the slab, gives rise to a velocity-dependent force contribution that is sensitive to the phase difference between the two polarization amplitudes. This term gives rise to a rather peculiar optical response on the moving body, and specific cases are illustrated for incident radiation of arbitrarily directed linear polarization. The additional force due to polarization mixing may cancel to first order in $V/c$ with the first order Doppler contribution yielding an overall vanishing of the velocity-dependent component of the force on the body. The above findings bear some relevance to modern developments of nano-optomechanics and to the problem of the frictional component of the Casimir force.