We propose a scheme to guide and funnel cold polar molecules above the surface of an insulating substrate (i.e., a molecular chip) using an electrostatic field generated by the combination of three parallel charged wires. We calculate the spatial distributions of the electric fields from the above charged-wire layout and their Stark potential for cold CO molecules, and analyze the relationships between the electric field and the geometric parameters of our charged-wire system. Also, we calculate and study the straight and bent guiding efficiency of cold polar molecules (including the guiding efficiency in our molecular funnel) by Monte Carlo simulation. Our study shows that the proposed charged-wire scheme can be used to realize the controllable surface guiding of cold polar molecules in the weak-field-seeking state on a chip, and form various integrated molecular optical elements, even to generate a continous wave cold molecular beam on a chip. In addition, our theoretically calculated results are in good agreement with ones of Monte Carlo simulation, and the guiding efficiency in our molecular funnel can be higher than 90%.

We study the phase diagram of a three-component Fermi gas with weak attractive interactions, which shows three superfluid and one normal phases. At weak symmetry breaking between the components the existence of domain walls interpolating between two superfluids introduces a new length scale much larger than the coherence length of each superfluid. This, in particular, limits the applicability of the local density approximation in the trapped case, which we also discuss. In the same regime the system hosts soft collective modes with a mass much smaller than the energy gaps of individual superfluids. We derive their dispersion relations at zero and finite temperatures and demonstrate that their presence leads to a significant enhancement of fluctuations near the superfluid-normal transitions.

We propose a method for observation of the quasistationary states of neutrons localized near a curved mirror surface. The bounding effective well is formed by the centrifugal potential and the mirror Fermi potential. This phenomenon is an example of an exactly solvable “quantum bouncer” problem that can be studied experimentally. It could provide a promising tool for studying fundamental neutron-matter interactions, as well as quantum neutron optics and surface physics effects. We develop a formalism that describes quantitatively the neutron motion near the mirror surface. The effects of mirror roughness are taken into account.

Photonic crystals built with time-reversal-symmetry-breaking Faraday-effect media can exhibit chiral edge modes that propagate unidirectionally along boundaries across which the Faraday axis reverses. These modes are precise analogs of the electronic edge states of quantum-Hall-effect (QHE) systems, and are also immune to backscattering and localization by disorder. The Berry curvature of the photonic bands plays a role analogous to that of the magnetic field in the QHE. Explicit calculations demonstrating the existence of such unidirectionally propagating photonic edge states are presented.

We develop a simple protocol for a one-shot version of quantum state redistribution, which is the most general two-terminal source coding problem. The protocol is simplified from a combination of protocols for the fully quantum reverse Shannon and fully quantum Slepian-Wolf problems, with its time-reversal symmetry being apparent. When the protocol is applied to the case where the redistributed states have a tensor power structure, more natural resource rates are obtained.

The dynamics of gap solitons in random gratings is studied. We show that the influence of disorder is averaged over the soliton width, so that the soliton acts as a low-pass filter. The averaging results in an effective potential, which can trap solitons. The statistical properties of the potential are found. We show that soliton trapping is related to level crossing by a random function, which allows us to find the mean number of soliton reflections and the mean distance between consecutive reflections.

We show that a difference in time scales of vertical and lateral dynamics permits one to analyze the problem of interacting electrons confined in an axially symmetric three-dimensional potential with a lateral oscillator confinement by means of the effective two-dimensional Hamiltonian with a screened Coulomb interaction. Using an adiabatic approximation based on action-angle variables, we present solutions for the effective charge of the Coulomb interaction (screening) for a vertical confinement potential simulated by parabolic, square, and triangular wells. While for the parabolic potential the solution for the effective charge is given in a closed analytical form, for the other cases similar solutions can be easily calculated numerically.

We calculate exact convergence times to reach random bipartite entanglement for various random protocols. The eigenproblem of a Markovian chain governing the process is mapped to a spin chain, thereby obtaining exact expression for the gap of the Markov chain for any number of qubits. For protocols coupling nearest-neighbor qubits and a controlled-NOT (CNOT) gate the mapping goes to the $XYZ$ model while for a U(4) gate it goes to an integrable $XY$ model. For coupling between a random pair of qubits the mapping is to an integrable Lipkin-Meshkov-Glick model. In all cases the gap scales inversely with the number of qubits, thereby improving on a recent bound [Phys. Rev. Lett. 98, 130502 (2007)].

The sum of ionization and charge-exchange cross sections of several gas targets (${\mathrm{H}}_2$, ${\mathrm{N}}_2$, He, Ne, Kr, Xe, Ar, and water vapor) impacted by a $1\text{−}\mathrm{MeV}$ ${\mathrm{K}}^{+}$ beam are measured. In a high-current ion beam, the self-electric field of the beam is high enough that ions produced from the gas ionization or charge exchange by the ion beam are quickly swept to the sides of the accelerator. The flux of the expelled ions is measured by a retarding field analyzer. This allows accurate measuring of the total charge-changing cross sections (ionization plus charge exchange) of the beam interaction with gas. Cross sections for ${\mathrm{H}}_2$, He, and Ne are simulated using classical trajectory Monte Carlo method and compared with the experimental results, showing good agreement.

The relation between scattering potential and ground-state energy shift of a helium atom (ion) close to a surface is investigated through use of a model of spatial limitation whereby the surface is represented by an infinitely rigid planar boundary. The model of an atom confined in a semi-infinite space with a plane boundary allows the variational evaluation of the ground-state energies and wave functions for He and ${\mathrm{He}}^{+}$ at different positions from the surface. The respective Born-Oppenheimer energy curves serve to model the ground-state energy shift for the elastic scattering channel in atom (ion) surface interactions. Independent calculations for the He-graphite and He-Al (111), (110), and (100) continuous planar potentials are carried out using high-quality ab initio calculations reported in the literature for the lowest He-C and He-Al binary interaction potentials. It is shown in this case that the He ground-state energy shift obtained within this model corresponds to an upper limit to the usual continuous planar potential. A discussion on the physical origin of this agreement is presented in terms of the static nature for the surface considered in both the hard-wall model and the atomic binary interactions used to construct the planar potentials, i.e., no account of the dynamic surface response is allowed as the projectile approaches. This is done by taking a reference pilot calculations based on electron nuclear dynamics for $100\mathrm{eV}$ He $\left({\mathrm{He}}^{+}\right)$-benzene $\left({\mathrm{C}}_6{\mathrm{H}}_6\right)$ interactions by considering the benzene molecule as a rough approximation to a local graphitic surface sector. It is found that the static planar potential provides a reasonable average representation of the interaction for neutral He, and supporting evidence for the use of the static O’Connor-Biersack potential is given. Finally, the effective scattering potential for $\mathrm{He}∕{\mathrm{He}}^{+}\text{−}\mathrm{Al}$ (111) is constructed through the use of the static planar potential for He-Al (111) considering the energy shift due to the classical image interaction for ${\mathrm{He}}^{+}$ approaching a perfectly Al (111) conducting plane before charge neutralization takes place. It is concluded that this scattering potential is directly related with the ground-state energy shift of the emerging already neutralized He atoms in $\mathrm{He}∕{\mathrm{He}}^{+}\text{−}\mathrm{Al}\left(111\right)$ grazing scattering experiments.

Control and optimization prospects in the frequency domain are studied theoretically, using a genetic algorithm (GA) and shaping Fourier-limited (FL) pulses. The objectives are state-to-state transitions and unitary transformations, within the scope of vibrational excitation of transition metal carbonyls. In analogy to experimental closed-loop setups, two different implementations of the phase function are investigated: a free phase variation and a sinusoidal phase modulation. We examine the control landscape generated by the parametrized phase functions and clarify the underlying mechanism. Strategies to decrease the complexity of the laser fields are developed, benefiting from previous optimal control theory calculations. Additionally, we pass the capabilities of the experiment and optimize the FL pulses with the GA simultaneously to the phase and transmittance functions. This allows us to predict promising FL-pulse properties and mask functions for future experiments.

A sufficiently large species imbalance (polarization) in a two-component Feshbach resonant Fermi gas is known to drive the system into its normal state. We show that the resulting strongly interacting state is a conventional Fermi liquid, that is, however, strongly renormalized by pairing fluctuations. Using a controlled $1∕N$ expansion, we calculate the properties of this state with a particular emphasis on the atomic spectral function, the momentum distribution functions displaying the Migdal discontinuity, and the radio frequency (rf) spectrum. We discuss the latter in the light of the recent experiments of [Schunck et al., Science 316, 867 (2007)] on such a resonant Fermi gas, and show that the observations are consistent with a conventional, but strongly renormalized Fermi-liquid picture.

We theoretically study polarization dynamics in the multitransverse-mode regime of a vertical-cavity surface-emitting laser subject to isotropic optical feedback. The contribution of each polarized transverse mode to the dynamics is elucidated. Polarization dynamics at fast time scales shows that polarized transverse modes demonstrate erratic pulsing. Anticorrelation between the two orthogonally polarized states is found. However, positive correlation between the orthogonal polarizations of the higher-order transverse mode appears. We also find a dynamical regime that shares many of the characteristics of the low frequency fluctuations. This regime corresponds to the onset of the external cavity peak and its harmonics in the polarized power spectra. Good agreement with recent experimental work [H. Lin et al., Phys. Rev. A 77, 033813 (2008)] has been found.

We study the interference patterns obtained from the superposition of two Bessel beams originated from a quantum two-photon state produced by a spontaneous parametric down-conversion process. Due to the nondiffracting character of the light beam, a self-imaging effect is found along the propagation direction for second-order interference patterns with periodicity proportional to $\lambda ∕2$, characterizing a two-photon Talbot effect. Conditional interference patterns in the longitudinal plane are theoretically shown as well.

We report on a frequency measurement of the $\left(3s^2\right){}^{1}S_0\to \left(3s3p\right){}^{3}P_1$ clock transition of ${}^{24}\mathrm{Mg}$ on a thermal atomic beam. The intercombination transition has been referenced to a portable primary Cs frequency standard with the help of a femtosecond fiber laser frequency comb. The achieved uncertainty is $2.5\times {10}^{-12}$, which corresponds to an increase in accuracy of six orders of magnitude compared to previous results. The measured frequency value permits the calculation of several other optical transitions from ${}^{1}S_0$ to the ${}^{3}P_J$-level system for ${}^{24}\mathrm{Mg}$, ${}^{25}\mathrm{Mg}$, and ${}^{26}\mathrm{Mg}$. We describe in detail the components of our optical frequency standard such as the stabilized spectroscopy laser, the atomic beam apparatus used for Ramsey-Bordé interferometry, and the frequency comb generator and discuss the uncertainty contributions to our measurement including the first- and second-order Doppler effect. An upper limit of $3\times {10}^{-13}$ in $1\mathrm{s}$ for the short-term instability of our optical frequency standard was determined by comparison with a quartz oscillator disciplined to the signal received from the global positioning system (GPS).

We present an experimental characterization of the statistics of multiple photon pairs produced by spontaneous parametric down-conversion realized in a nonlinear medium pumped by high-energy ultrashort pulses from a regenerative amplifier. The photon-number-resolved measurement has been implemented with the help of a fiber loop detector. We introduce an effective theoretical description of the observed statistics based on parameters that can be assigned direct physical interpretation. These parameters, determined for our source from the collected experimental data, characterize the usefulness of down-conversion sources in multiphoton interference schemes that underlie protocols for quantum-information processing and communication.

We present a method for describing and characterizing the state of $N$ particles that may be distinguishable in principle but not in practice due to experimental limitations. The technique relies upon a careful treatment of the exchange symmetry of the state among experimentally accessible and experimentally inaccessible degrees of freedom. The approach we present allows a formalization of the notion of indistinguishability and can be implemented easily using currently available experimental techniques. Our work is of direct relevance to current experiments in quantum optics, for which we provide a specific implementation.

Jahn-Teller systems and the Jahn-Teller effect are discussed in terms of cavity QED models. By expressing the field modes in a quadrature representation, it is shown that certain setups of a two-level system interacting with a bimodal cavity are described by the Jahn-Teller $E\times \epsilon$ Hamiltonian. We identify the corresponding adiabatic potential surfaces and the conical intersection. The effects of a nonzero geometrical Berry phase, governed by encircling the conical intersection, are studied in detail both theoretically and numerically. The numerical analysis is carried out by applying a wave packet propagation method, more commonly used in molecular or chemical physics, and analytic expressions for the characteristic time scales are presented. It is found that the collapse-revival structure is greatly influenced by the geometrical phase and as a consequence, the field intensities contain direct information about this phase. We also mention the link between the Jahn-Teller effect and the Dicke phase transition in cavity QED.

We experimentally show the existence of labyrinthine patterns between spatially modulated steady states in a simple nonlinear optical system consisting of a sodium vapor cell and a single feedback mirror. The inhomogeneity of the steady states leads to a locking phenomenon determining the length scale of the labyrinthine patterns and diminishes their region of existence in favor of localized periodic patterns. Numerical simulations confirm the experimental observations.