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The article discusses various concepts related to modern physics. It explains Einstein's theory, the effect of intensity of light and potential on photoelectric current, Bohr's model of hydrogen-like atoms, and atomic spectra. It also discusses the limitations of Bohr's model and how it cannot be extended to even two atoms such as helium.

The article focuses on the topics from the Physics NCERT (National Council of Educational Research and Training) syllabus that has been frequently asked in the past 10 years in exams. It covers various topics such as ray optics and optical instruments, dispersion of light through a glass prism, optical fibre, refraction at a spherical surface, and lenses. It further explains the concepts of atmospheric refraction, Snell's law, and the formation of images using equations and diagrams.

Thermo Fisher Scientific has been granted a patent for an optical emission spectrometry method and apparatus. This technique is used to analyze samples and determine their constituent molecules or atoms. The patent specifically addresses the challenge of detecting ultraviolet atomic emission lines, which are important for analyzing elements like carbon, nitrogen, sulfur, and oxygen. The invention utilizes absorption spectroscopy to measure the transmittance of the purge gas within the spectrometer and dynamically control the gas flow to achieve a stable transmittance level quickly and with reduced gas consumption. The patent provides detailed claims and descriptions of the method and apparatus, making it particularly useful for researchers in optical emission spectrometry. [Extracted from the article]

A study conducted by researchers at Central China Normal University in Wuhan, People's Republic of China, explores the effects of various factors on the performance of portable self-oscillating magnetometers. The researchers examined the impact of laser intensity, resonance detuning, radio frequency magnetic field, and atomic cell on the magnetometers' performance. By analyzing the influencing factors on the atomic magnetic resonance signal, the researchers were able to optimize the parameters of the magnetometers. The study provides valuable insights for improving the performance of these devices, which are widely used in fields such as biomedicine and remote sensing. [Extracted from the article]

A new report discusses research conducted by the National Institute of Advanced Industrial Science and Technology (NIAIST) in Ibaraki, Japan, on the estimation of average molecular structural parameters of heavy hydrocarbons using infrared spectroscopy. Heavy hydrocarbons, such as coal tars and petroleum residues, are inexpensive raw materials for carbon fiber production. The study developed an alternative approach to determine the average structural models of these heavy hydrocarbons using small sample quantities and accommodating insoluble materials. The research concluded that equations predicting various parameters were determined using infrared spectra and hydrogen-to-carbon atomic ratios of different samples. This research has been peer-reviewed and published in the Journal of the Japan Petroleum Institute. [Extracted from the article]

The article focuses on a research study on the spectrum of atomic hydrogen. Researchers consider the spectrum of hydrogen as an important part of the modern physics. The analysis of these atoms will open way for various other studies. Laser, which is a tool of spectroscopy has been proved a great help in the analysis of the spectrum. The researchers have established that a pattern of distinct lines is formed when the light emitted by hydrogen atoms is dispersed according to the wavelength.

X-ray absorption and X-ray magnetic circular dichroism (XMCD) are very powerful tools for probing the orbital and spin moments of each atomic species orbital of magnetic materials. In this work, we present the implementation of a module for computing the X-ray absorption and XMCD spectra into the VASP code. We provide a derivation of the absorption cross-section in the electric dipole approximation. The matrix elements, which make up the X-ray absorption cross-section for a given polarization of light, are then computed using either the momentum operator p or the position operator r , within the projector augmented wave method. The core electrons are described using the relativistic basis-set whereas for the valence electrons, the spin–orbit coupling is added perturbatively to the semi-relativistic Hamiltonian. We show that both the p and the r implementations lead to the same results. The results for the K-edge and L 23 -edges of b c c -iron are then computed and compared to experiment. [ABSTRACT FROM AUTHOR]

The article discusses the advances and applications of back-illuminated charge-coupled device (CCD). It explains how back-illuminated, or back-thinned, CCDs are manufactured and how the two new silicon- based CCD sensors such as the HR-sensors and LD-sensors operate. Results of the three experiments for HR-sensor which showed the advantages offered by the HR-sensors in the acquisition of atomic spectra, the good correlation between spectra produced by each camera are discussed.

We experimentally study the breakdown of hyperfine coupling for an atom in a deep optical-dipole trap. One-color laser spectroscopy is performed at the resonance lines of a single 87Rb atom for a trap wavelength of 1064 nm. Evidence of hyperfine breakdown comes from three observations, namely, a nonlinear dependence of the transition frequencies on the trap intensity, a splitting of lines which are degenerate for small intensities, and the ability to drive transitions which would be forbidden by selection rules in the absence of hyperfine breakdown. From the data, we infer the hyperfine interval of the 5P1/2 state and the scalar and tensor polarizabilities for the 5P3/2 state. [ABSTRACT FROM AUTHOR]

We consider the dynamics of intracavity electromagnetically induced transparency (EIT) in an ensemble of strongly interacting Rydberg atoms. By combining the advantage of variable cavity lifetimes with intracavity EIT and strongly interacting Rydberg dark-state polaritons, we show that such an intracavity EIT system could exhibit a very strong photon blockade effect. [ABSTRACT FROM AUTHOR]

We calculate interspecies Rydberg-Rydberg interaction strengths for the heavy alkali metals Rb and Cs. The presence of strong Forster resonances makes interspecies coupling a promising approach for long-range entanglement generation. We also provide an overview of the strongest Förster resonances for Rb-Rb and Cs-Cs using different principal quantum numbers for the two atoms. We show how interspecies coupling can be used for high fidelity quantum nondemolition state measurements with low cross-talk in qubit arrays. [ABSTRACT FROM AUTHOR]

We study the repulsive van der Waals interaction of cold rubidium 70S1/2 Rydberg atoms by analysis of time-delayed pair-correlation functions. After excitation, Rydberg atoms are allowed to accelerate under the influence of the van der Waals force. Their positions are then measured using a single-atom imaging technique. From the average pair-correlation function of the atom positions we obtain the initial atom-pair separation and the terminal velocity, which yield the van der Waals interaction coefficient C6. The measured C6 value agrees well with calculations. The experimental method has been validated by simulations. The data hint at anisotropy in the overall expansion, caused by the shape of the excitation volume. Our measurement implies that the interacting entities are individual Rydberg atoms, not groups of atoms that coherently share a Rydberg excitation. [ABSTRACT FROM AUTHOR]

We report the creation of ultra-long-range Sr² molecules comprising one ground-state 5s² ¹SO atom and one atom in a 5sns ³S1 Rydberg state for n ranging from 29 to 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation near resonant with the 5S5p³P1 intermediate state, and their formation is detected through ground-state atom loss from the trap. The observed molecular binding energies are reproduced with the aid of first-order perturbation theory that utilizes a Fermi pseudopotential with effective s-wave and p-wave scattering lengths to describe the interaction between an excited Rydberg electron and a ground-state Sr atom. [ABSTRACT FROM AUTHOR]

The determination of many special types of quantum states has been studied thoroughly, such as the generalized ||GHZ> states, stochastic local operations and classical communication equivalent |W> states, and Dicke states. In this paper, we study another special entanglement state, that is, stabilizer states, which play an important role in quantum error correcting codes, multipartite purification, and so on. We show that all n-qubit stabilizer states are uniquely determined (among arbitrary states, pure or mixed) by their reduced density matrices for systems which are the supports of n independent generators of the corresponding stabilizer formalisms. [ABSTRACT FROM AUTHOR]

Dark matter in the Milky Way may annihilate directly into γ rays, producing a monoenergetic spectral line. Therefore, detecting such a signature would be strong evidence for dark matter annihilation or decay. We search for spectral lines in the Fermi Large Area Telescope observations of the Milky Way halo in the energy range 200 MeV-500 GeV using analysis methods from our most recent line searches. The main improvements relative to previous works are our use of 5.8 years of data reprocessed with the Pass 8 event-level analysis and the additional data resulting from the modified observing strategy designed to increase exposure of the Galactic center region. We search in five sky regions selected to optimize sensitivity to different theoretically motivated dark matter scenarios and find no significant detections. In addition to presenting the results from our search for lines, we also investigate the previously reported tentative detection of a line at 133 GeV using the new Pass 8 data. [ABSTRACT FROM AUTHOR]

In many areas of physics, the Kramers-Kronig relations are used to extract information about the real part of the optical response of a medium from its imaginary counterpart. In this paper we discuss an alternative but mathematically equivalent approach based on the Hilbert transform. We apply the Hilbert transform to transmission spectra to find the group and refractive indices of a Cs vapor and thereby demonstrate how the Hilbert transform allows indirect measurement of the refractive index, group index, and group delay while avoiding the use of complicated experimental setups. [ABSTRACT FROM AUTHOR]

We present a detailed theoretical study on the photoionization from the bound excited ¹P state of He to continua dominated by multiple doubly excited resonance series embedded in multiple single-ionization channels between the N = 2 and N = 3 thresholds. In addition to identifying the individual resonance series, our investigation has also demonstrated unambiguously the level crossing between overlapping resonance series and how the closely spaced pairs of resonances migrate as energy increases. [ABSTRACT FROM AUTHOR]

This Brief Report gives the spectral distribution of the supercontinuum generated from a system of initially partially excited two-level atoms. The expansion in the eigenfunctions of the one-dimensional Liénard-Wiechert kernel which was successful in obtaining previously the results in the linear regime is generalized to the nonlinear regime. The detailed spectral distribution of the emitted radiation is computed without invoking either the phenomenological simplified physical model for the active medium or the mathematical approximations commonly used in treating propagation in absorbing media. The numerical solutions presented are those of the complete set of the coupled Maxwell-Bloch equations. [ABSTRACT FROM AUTHOR]

We present the observations of the phase differences Δ∅HH(2n) between adjacent high-order harmonics generated from Ar and N2 at the near-threshold region. The Δ∅HH(2n)'s are extracted from the photoelectron signals resulting from two-color two-photon ionization of rare-gas atoms, which are produced by high-order harmonics to be measured and a part of the fundamental pulse for probing. An analysis method is employed to remove the inevitable modulations in high-order-harmonic intensities based on the underlying mechanism of the production of photoelectrons. We find a significant difference in the Δ∅HH(2n) at the nearest-threshold order between Ar and N2. This difference cannot be reproduced by the model calculation by using the saddle-point method within the strong-field approximation. To elucidate the origin of the difference between the Δ∅HH(2n) for Ar and that for N2, we note the fact that the phase difference Acontains information both on the recombination time tr of the freed electron and on the phase of the recombination dipole moment d*. With the help of some numerical calculations, we discuss the effect of the potential created by the parent ion on tr and d* which are neglected in the strong-field approximation. [ABSTRACT FROM AUTHOR]

The Fano resonance theory is modified to account for photoionization by ultrashort laser pulses where the probability definition due to the nonlinear dependence on time is no longer valid. We employ the exact integrals over the Fourier transform of the photoionization cross section including the Fano resonances and a corrected Gaussian pulse shape that has vanishing electric field for zero frequency. Numerical results are presented for neutral helium that allow us to deduce the spectral distribution of the Fano resonance for different parameters and to identify the cases where the linear regime is invalid. Analytical approximations are given that provide a clear understanding of the linear and nonlinear regime related to the Fano parameter q, the detuned carrier frequencies, and pulse durations. [ABSTRACT FROM AUTHOR]

The observation of features, often referred to as "Wigner cusps" in a scattering cross section at the opening of a new scattering channel has been widely reported in electron scattering, and has been attributed to strong coupling between the two scattering channels. Recently a series of cusps were observed in positron scattering from the noble gases [A. C. L. Jones etal., Phys. Rev. Lett. 105, 073201 (2010)]. In this case, the strong opening of the positronium formation cross section resulted in a cusplike feature, or bump, in the total elastic scattering cross section. The positronium formation channel is typically the largest partial scattering cross section in the region of the electronic excitation and ionization thresholds in most atoms and molecules, and it is plausible that similar features may exist in other atomic and molecular species. We have undertaken measurements of the isoelcctronic targets of helium--H2, and neon--H2O, NH3, and CH4, in an effort to better understand the mechanisms leading to these threshold features. [ABSTRACT FROM AUTHOR]

Motivated by a recent experiment by the Ecole Normale Supérieure de Lyon (ENS) group on the mixture of Bose and Fermi superfluids [I. Ferrier-Barbut et al., Science 345, 1035 (2014)], we investigate the effective scattering between a bosonic atom and a molecule (dimer) of fermion atoms. It is found that the mean-field prediction of the atom-dimer scattering length (aad), as simply given by the boson-fermion scattering length (abf), generically fails. Instead, aad crucially depends on the ratio between abf and aff (the fermion-fermion scattering length), and in addition it log-periodically depends on the three-body parameter. We identify the universal parameters in characterizing aad for a wide range of aff in the molecular side of the fermion-fermion Feshbach resonance, and further demonstrate that the atom-dimer many-body system can become unstable against either phase separation or collapse as tuning aff. Our results have some implications for the ENS experiment. [ABSTRACT FROM AUTHOR]

The nonequilibrium dynamics of a gas of cold atoms in which Rydberg states are off-resonantly excited is studied in the presence of noise. The interplay between interaction and off-resonant excitation leads to an initial dynamics where aggregates of excited Rydberg atoms slowly nucleate and grow, eventually reaching long-lived metastable arrangements which then relax further on much longer time scales. This growth dynamics is governed by an effective Master equation which permits a transparent and largely analytical understanding of the underlying physics. By means of extensive numerical simulations we study the many-body dynamics and the correlations of the resulting nonequilibrium states in various dimensions. Our results provide insight into the dynamical richness of strongly interacting Rydberg gases in noisy environments, and highlight the usefulness of these kinds of systems for the exploration of soft-matter-type collective behavior. [ABSTRACT FROM AUTHOR]

The Pauli exclusion principle requires the spectrum of the occupation numbers of the one-electron reduced density matrix (1-RDM) to be bounded by one and zero. However, for a 1-RDM from a wave function, there exist additional conditions on the spectrum of occupation numbers, known as pure N-representability conditions or generalized Pauli conditions. For atoms and molecules, we measure through a Euclidean-distance metric the proximity of the 1-RDM spectrum to the facets of the convex set (polytope) generated by the generalized Pauli conditions. For the ground state of any spin symmetry, as long as time-reversal symmetry is considered in the definition of the polytope, we find that the 1-RDM's spectrum is pinned to the boundary of the polytope. In contrast, for excited states, we find that the 1-RDM spectrum is not pinned. Proximity of the 1-RDM to the boundary of the polytope provides a measurement and classification of electron correlation and entanglement within the quantum system. For comparison, this distance to the boundary of the generalized Pauli conditions is also compared to the distance to the polytope of the traditional Pauli conditions, and the distance to the nearest 1-RDM spectrum from a Slater determinant. We explain the difference in pinning in the ground- and excited-state 1-RDMs through a connection to the N-representability conditions of the two-electron reduced density matrix. [ABSTRACT FROM AUTHOR]

We present an improved superatom model for examining nonlinear optical responses of cold Rydberg atoms in the regime of electromagnetically induced transparency (EIT). By going beyond the weak-probe approximation, we find that several higher-order collective states should be included to correctly describe the coherent Rydberg excitation of superatoms. Otherwise, numerical results based on the simple ladder system of superatoms will contribute wrong predictions on light intensity and photon correlation of the transmitted probe field. In particular, a great photon-bunching effect will be improperly expected somewhere out of the EIT window in one dilute atomic sample. The essence of this improved superatom model lies in that it can provide reliable predictions on the nonlinear Rydberg-EIT phenomena even in dense atomic samples and may be extended to realize lossless conditional light interactions in appropriate multilevel systems exhibiting dipole blockade. [ABSTRACT FROM AUTHOR]

We study the three-dimensional nature of the quantum interface between an ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled through a dispersive interaction. To achieve strong entanglement between the collective atomic spin and the photons, one must match the spatial mode of the collective radiation of the ensemble with the mode of the laser beam while minimizing the effects of decoherence due to optical pumping. For ensembles coupling to a probe field that varies over the extent of the cloud, the set of atoms that indistinguishably radiates into a desired mode of the field defines an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is not characterized by a single parameter, the optical density, but by a collection of different effective atom numbers that characterize the coherence and decoherence of the system. To model the dynamics of the system, we develop a full stochastic master equation, including coherent collective scattering into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and backaction due to continuous measurement of the light entangled with the spin waves. This formalism is used to study the squeezing of a spin wave via continuous quantum nondemolition measurement. We find that the greatest squeezing occurs in parameter regimes where spatial inhomogeneities are significant, far from the limit in which the interface is well approximated by a one-dimensional, homogeneous model. [ABSTRACT FROM AUTHOR]

We recently used a compact Penning trap to capture and isolate highly charged ions extracted from an electron beam ion trap (EBIT) at the National Institute of Standards and Technology. Isolated charge states of highly stripped argon and neon ions with total charge Q ⩾ 10, extracted at energies of up to 4 × 103 Q eV, are captured in a trap with well depths of ≈(4-12)Q eV. Here we discuss in detail the process to optimize velocity tuning, capture, and storage of highly charged ions in a unitary Penning trap designed to provide easy radial access for atomic or laser beams in charge exchange or spectroscopic experiments, such as those of interest for proposed studies of one-electron ions in Rydberg states or optical transitions of metastable states in multiply charged ions. Under near-optimal conditions, ions captured and isolated in such rare-earth Penning traps can be characterized by an initial energy distribution that is ≈60 times narrower than typically found in an EBIT. This reduction in thermal energy is obtained passively, without the application of any active cooling scheme in the ion-capture trap. [ABSTRACT FROM AUTHOR]

We use direct spatial ion imaging of cold 85Rb Rydberg atom clouds to measure the Rydberg-Rydberg correlation function, with and without light-shift potentials generated by an optical dipole trap. We find that the blockade radius depends on laser detunings and spatially varying light shifts. At certain laser detunings the probability of exciting Rydberg atoms at particular separations is enhanced, which we interpret to be a result of direct two-photon excitation of Rydberg atom pairs. The results are in accordance with predictions [F. Robicheaux and J. V. Hernandez, Phys. Rev. A 72, 063403 (2005)] and a model we develop that accounts for a one-dimensional dipole-trap potential. [ABSTRACT FROM AUTHOR]

We report the realization of a matter-wave interferometer based on Raman transitions which simultaneously interrogates two different atomic species (87Rb and 85Rb). The simultaneous aspect of our experiment presents encouraging preliminary results for future dual-species atom interferometry projects and seems very promising by taking advantage of a differential acceleration measurement. Indeed, the resolution of our differential accelerometer remains lower than 3.9×10-8 g even with vibration levels up to 1×10-3 g thanks to common-mode vibration noise rejection. An atom-based test of the weak equivalence principle has also been carried out leading to a differential free fall measurement between both isotopes of Δg/g=(1.2±3.2)×10-7. [ABSTRACT FROM AUTHOR]

We present an optimal protocol to implement a room-temperature Rydberg single-photon source within an experimental setup based on micro cells filled with thermal vapor. The optimization of a pulsed four wave mixing scheme allows us to double the effective Rydberg blockade radius as compared to a simple Gaussian pulse scheme, releasing some of the constraints on the geometry of the micro cells. The performance of the optimized protocol is improved by about 70% with respect to the standard protocol. [ABSTRACT FROM AUTHOR]

We show that multipulse excitation of Rydberg atoms with a sequence of short time-delayed femtosecond pulses results in strong n selection of the final-state amplitudes. In the experiment, a 150 fs laser pulse, which alone populates n levels from 22-32 in Li, is chopped into four time-delayed excitation pulses, which results in a strong modification of the n-level distribution. The mechanism demonstrated in the experiment is derived theoretically: With more pulses, it is shown that the population of a single or a few n levels can be performed on demand and varied as long as the central laser frequency is given. [ABSTRACT FROM AUTHOR]

We characterize the effect of quantum interference on the line shapes and measured line positions in atomic spectra. These effects, which occur when the excited-state splittings are of order of the natural line widths, represent an overlooked but significant systematic effect. We show that excited-state interference gives rise to non-Lorentzian line shapes that depend on excitation polarization, and we present expressions for the corrected line shapes. We present spectra of 6,7Li D lines taken at multiple excitation laser polarizations and show that failure to account for interference changes the inferred line strengths and shifts the line centers by as much as 1 MHz. Using the correct line shape, we determine absolute optical transition frequencies with an uncertainty of ≼25 kHz and provide an improved determination of the difference in mean-square nuclear charge radii between 6Li and 7Li. This analysis should be important for a number of high-resolution spectral measurements that include partially resolvable atomic lines. [ABSTRACT FROM AUTHOR]

We investigate the spontaneous emission of a two-level atom placed in the vicinity of a plasmonic cloak composed of a coated sphere. In the dipole approximation, we show that the spontaneous emission rate can be reduced to its vacuum value provided the atomic emission frequency lies within the plasmonic cloak frequency operation range. Considering the current status of plasmonic cloaking devices, this condition may be fulfilled for many atomic species so that we argue that atoms with a sufficiently strong transition can be used as quantum, local probes for the efficiency of plasmonic cloaks. [ABSTRACT FROM AUTHOR]

The modeling of complex atomic spectra is a difficult task, due to the huge number of levels and lines involved. In the presence of a magnetic field, the computation becomes even more difficult. The anomalous Zeeman pattern is a superposition of many absorption or emission profiles with different Zeeman relative strengths, shifts, widths, asymmetries, and sharpnesses. We propose a statistical approach to study the effect of a magnetic field on the broadening of spectral lines and transition arrays in atomic spectra. In this model, the a and n profiles are described using the moments of the Zeeman components, which depend on quantum numbers and Lande factors. A graphical calculation of these moments, together with a statistical modeling of Zeeman profiles as expansions in terms of Hermite polynomials are presented. It is shown that the procedure is more efficient, in terms of convergence and validity range, than the Taylor-series (TS) expansion in powers of the magnetic field, which was suggested in the past. Finally, a simple approximate method to estimate the contribution of a magnetic field to the width of transition arrays is proposed. It relies on our recently published recursive technique for the numbering of LS terms of an arbitrary configuration. [ABSTRACT FROM AUTHOR]

We discuss a candidate solution for the controlled trapping and manipulation of two individual Rydberg atoms by means of a magnetic Ioffe-Pritchard trap that is superimposed by a constant electric field. In such a trap Rydberg atoms experience a permanent electric dipole moment that can be of the order of several hundred debye. The interplay of electric dipolar repulsion and three-dimensional magnetic confinement leads to a well controllable equilibrium configuration with tunable trap frequency and atomic distance. We thoroughly investigate the trapping potentials and analyze the interaction-induced stabilization of two such trapped Rydberg atoms. Possible limitations and collapse scenarios are discussed. [ABSTRACT FROM AUTHOR]

Photoassociation (PA) dynamics of ultracold cesium atoms steered by a modulated two-color laser field Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed is investigated theoretically by numerically solving the time-dependent Schrödinger equation. The PA dynamics is sensitive to the phase of envelope (POE) φ and the period of the envelope Tp, which indicates that it can be controlled by varying POE φ and period Tp. Moreover, we introduce the time- and frequency-resolved spectrum to illustrate how the POE φ and the period Tp influence the intensity distribution of the modulated laser pulse and hence change the time-dependent population distribution of photoassociated molecules. When the Gaussian envelope contains a few oscillations, the PA efficiency is also dependent on POE φ. The modulated two-color laser field is available in the current experiment based on laser mode-lock technology. [ABSTRACT FROM AUTHOR]

We examine spectral properties on one-dimensional (1D) trapped ultracold Fermi atoms loaded on optical lattices by using the dynamical density-matrix renormalization group (DDMRG) method. We find that spectra are very rich due to the interplay of free or repulsive interaction and the harmonic-trap potential. One of the rich examples is that a 1D Tomonaga-Luttinger (TL) liquid spectrum emerges beneath multiple bound-state fiat levels in the Mott-plateau phase and the TL spectrum gradually disappears with a partial breakdown of the central Mott plateau by increasing the trap strength. A more striking example is the growth of a distinct low-energy broadened band from the bound-state fiat levels together with the breakdown. It demonstrates a carrier doping effect into the Mott phase in optical lattice systems. [ABSTRACT FROM AUTHOR]

We propose blue-detuned optical traps that are suitable for trapping of both ground-state and Rydberg excited atoms. The addition of a background compensation field or a suitable choice of the trap geometry provides a magic trapping condition for ground-state and Rydberg atoms at the trap center. Deviations from the magic condition at finite temperature are calculated. Designs that achieve less than 200-kHz differential trap shift between Cs ground states and 125s Rydberg states for 10 µK Cs atoms are presented. Consideration of the trapping potential and photoionization rates suggests that these traps will be useful for quantum-information experiments with atomic qubits. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally and theoretically that the spatial distribution of high-angular-momentum Rydberg wave packets, and thus off-diagonal elements of the density matrix, can be probed in detail through extraction of the moments of the position distribution (λ = 1,2) from quantum beat revivals. Detailed knowledge of the position distribution allows precise manipulation of the wave packet which is demonstrated by the control of its n distribution. [ABSTRACT FROM AUTHOR]

We study a dilute sample of cold atoms to achieve efficient population transfer from a ground state to a Rydberg state. This sample is approximately divided into many independent microspheres containing only two atoms. Each pair of atoms in a microsphere may become quantum correlated via the dipole-dipole interaction characterized by a van der Waals potential. Our numerical results show that, by modulating detunings of a pump pulse and a Stokes pulse applied in the counterintuitive order, we can drive the dilute sample either into the blockade regime or into the antiblockade regime. In the blockade regime, only one atom is allowed to be coherently transferred into the Rydberg state in a microsphere, which then results in a maximal entangled state. In the antiblockade regime, however, both atoms in a microsphere can be efficiently excited into the Rydberg state, which is not accompanied by quantum entanglement. A second maximal entangled state may also be generated if we work between the blockade regime and the antiblockade regime. Note that the existence of a quasidark state is essential for exciting both atoms in a microsphere into the Rydberg state when the van der Waals potential is nonzero. [ABSTRACT FROM AUTHOR]

We present a method for amplifying a single or scattered impurities immersed in a background gas of ultracold atoms so that they can be optically imaged and spatially resolved. Our approach relies on a Raman transfer between two stable atomic hyperfine states that is conditioned on the presence of an impurity atom. The amplification is based on the strong interaction among atoms excited to Rydberg states. We perform a detailed analytical study of the performance of the proposed scheme with particular emphasis on the influence of inevitable many-body effects. [ABSTRACT FROM AUTHOR]

We have excited helium atoms from their metastable 2 ³S state to Rydberg states in the range 13 < n < 50 in a two-step process via the 3 ³P state using light at λ = 389 nm and 785-815 nm. Atoms in a thermal beam (100 K) cross partially overlapping laser beams of the appropriate frequencies in the counterintuitive order to exploit the high efficiency of stimulated rapid adiabatic passage. The interaction region is between two plates that can be used for Stark tuning in a few V/cm field or for field ionization. At fields much too low for field ionization, we observe signals attributed to ionization by blackbody radiation. Multiple tests confirm this attribution as the cause of ionization. For example, by heating the plates we observe the expected signal increases. Our experiments reinforce previous work where the interaction between Rydberg atoms and room temperature blackbody radiation is important for experiments. [ABSTRACT FROM AUTHOR]

Frequency-resolved observations of heavy Rydberg states in molecular hydrogen are reported in the ungerade manifold of states. Double-resonance spectroscopy via the E,F 1Σg+, v′=6 state has been used to probe the energy region above the H(1s) + H(3l) dissociation threshold. Resonances are observed by ionizing H(3l) to produce H+, which is then detected by using a time-of-flight mass spectrometer. The kinetic energy of the H+ ion confirms that the observed signal is due to the photoionization of neutral H(3l) atoms, indicating that dissociation is a significant decay channel for the ion-pair states. The pattern of energies of the resonances agree well with the predictions of a mass-scaled Rydberg formula for bound quantum states of the H+H- ion pair. Energies and quantum defects have been determined for principal quantum numbers in the range of n=130 to 207. [ABSTRACT FROM AUTHOR]

High-resolution studies of the fine-structure pattern in high-L n = 37 levels of Th3+ have been carried out using radio-frequency (rf) spectroscopy detected with resonant excitation Stark ionization spectroscopy (RESIS). Intervals separating L = 9 to L = 15 levels have been measured, and the results analyzed with the long-range effective potential model. The dipole polarizability of Th4+is determined to be αD = 7.720(7) a.u. The quadrupole polarizability is found to be 21.5(3.9) a.u. Both measurements represent significant tests of a priori theoretical descriptions of this highly relativistic ion. [ABSTRACT FROM AUTHOR]

A constraint on a spin-dependent interaction, induced by a pseudovector light boson, is presented. The interaction includes a Yukawa-type contribution α″(s1∙s2)e-λr/r and a contact spin-spin term. To disentangle the long-range and contact terms we utilize experimental data on the 1s and 2s hyperfine intervals for light two-body atoms and construct a specific difference 8×Ehfs(2s)-Ehfs(1s). That allows one to constrain the spin-dependent coupling constant α″ of an electron-nucleus Yukawa-type interaction in hydrogen, deuterium, and the helium-3 ion at the level below a part in 1016. The derived constraint is related to the range of masses below 4 keV/c2. The combined constraint including the contact terms is also presented. [ABSTRACT FROM AUTHOR]

Prior to recombination photons, electrons, and atomic nuclei rapidly scattered and behaved, almost, like a single tightly-coupled photon-baryon plasma. We investigate here the accuracy of the tight-coupling approximation commonly used to numerically evolve the baryon and photon perturbation equations at early times. By solving the exact perturbations equations with a stiff solver starting deep in the radiation-dominated epoch, we find the level of inaccuracy introduced by resorting to the standard first-order tight-coupling approximation. We develop a new second-order approximation in the inverse Thomson opacity expansion and show that it closely tracks the full solution, at essentially no extra numerical cost. We find the bias on estimates of cosmological parameters introduced by the first-order approximation is, for most parameters, negligible. Finally, we show that our second-order approximation can be used to reduce the time needed to compute cosmic microwave background angular spectra by as much as ∼17%. [ABSTRACT FROM AUTHOR]

The problem of photonic phase transition for the system of a two-level atomic ensemble interacting with a quantized single-mode electromagnetic field in the presence of optical collisions (OCs) is considered. We have shown that for large and negative atom-field detuning a photonic field exhibits high-temperature second-order phase transition to superradiant state under thermalization condition for coupled atom-light states. Such a transition can be connected with superfluid (coherent) properties of photonlike low branch (LB) polaritons. We discuss the application of metallic cylindrical waveguide for observing predicted effects. [ABSTRACT FROM AUTHOR]

We develop the auxiliary field formalism corresponding to a dilute system of spin-1/2 fermions. This theory represents the Fermi counterpart of the Bose-Einstein condensation (BEC) theory developed recently by F. Cooper et al. Phys. Rev. Lett. 105 240402 (2010) ] to describe a dilute gas of Bose particles. Assuming tunable interactions, this formalism is appropriate for the study of the crossover from the regime of Bardeen-Cooper-Schriffer (BCS) pairing to the regime of BEC in ultracold fermionic atom gases. We show that when applied to the Fermi case at zero temperature, the leading-order auxiliary field (LOAF) approximation gives the same equations as obtained in the standard BCS variational picture. At finite temperature, LOAF leads to the theory discussed by Sá de Melo, Randeria and Engelbrecht Phys. Rev. Lett. 71 3202 (1993) ; Phys. Rev. B 55 15153 (1997) ]. As such, LOAF provides a unified framework to study the interacting Fermi gas. The mean-field results discussed here can be systematically improved on by calculating the one-particle irreducible action corrections, order by order. [ABSTRACT FROM AUTHOR]

We study the spin-mixing dynamics of ultracold spin-1 atoms in a weak nonuniform magnetic field with field gradient G, which can flip the spin from +1 to -1 so that the magnetization m=ρ+-ρ- is not a constant anymore. The dynamics of mF=0 Zeeman component ?0, as well as the system magnetization m, are illustrated for both ferromagnetic and polar interaction cases in the mean-field theory. We find that the dynamics of system magnetization can be tuned between the Josephson-like oscillation similar to the case of double well and the interesting self-trapping regimes, i.e., the spin-mixing dynamics sustains a spontaneous magnetization. Meanwhile, the dynamics of ρ0 may be sufficiently suppressed for initially imbalanced number distribution in the case of polar interaction. A "beat-frequency"oscillation of the magnetization emerges in the case of balanced initial distribution for polar interaction, which vanishes for ferromagnetic interaction. [ABSTRACT FROM AUTHOR]

We report the magnetic merging of ultracold atomic gases of 85Rb and 87Rb by the controlled overlap of two initially spatially separated magnetic traps. We present a detailed analysis of the combined magnetic-field potential as the two traps are brought together that predicts a clear optimum trajectory for the merging. We verify this prediction experimentally using 85Rb and find that the final atom number in the merged trap is maximized with minimal heating by following the predicted optimum trajectory. Using the magnetic-merging approach allows us to create variable-ratio isotopic Rb mixtures with a single laser-cooling setup by simply storing one isotope in a magnetic trap before jumping the laser frequencies to the transitions necessary to laser cool the second isotope. [ABSTRACT FROM AUTHOR]