Physical Review A

We propose an experiment that would produce and measure a large Aharonov-Casher (AC) phase in a solid-state system under macroscopic motion. A diamond crystal is mounted on a spinning disk in the presence of a uniform electric field. Internal magnetic states of a single nitrogen-vacancy (N-V) defe...

Recently, the principle of information causality has appeared as a good candidate for an information-theoretic principle that would single out quantum correlations among more general nonsignaling models. Here, we present results going in this direction, namely, we show that part of the boundary of q...

The noncontextuality of quantum mechanics can be directly tested by measuring two entangled particles with more than two outcomes per particle. The two associated contexts are “interlinked” by common observables.

We show that the canonical phase measurement is pure in the sense that the corresponding positive operator valued measure (POVM) is extremal in the convex set of all POVMs. This means that the canonical phase measurement cannot be interpreted as a noisy measurement even if it is not a projection val...

We introduce quantum spin models whose ground states allow for sizable entanglement between distant spins. We discuss how spin models with global end-to-end entanglement realize quantum teleportation channels with optimal compromise between scalability and resilience to thermal decoherence and can b...

A scheme for fault-tolerant quantum computation (FTQC) with probabilistic two-qubit gates is proposed. The error thresholds for FTQC are estimated by numerical simulations, where the conditional error probability (the error probability under the condition of “success”) is taken into account in a...

Invariant entangled states remain unchanged under simultaneous identical unitary transformations of all their subsystems. We experimentally generate and characterize such invariant two-, four-, and six-photon polarization entangled states. This is done only with a suitable filtering procedure of mul...

The two-loop self-energy correction to the ground-state Lamb shift is calculated for hydrogenlike ions with the nuclear charge Z=10–30 without any expansion in the binding field of the nucleus. A calculational technique is reported for treatment of Feynman diagrams in the mixed coordinate-moment...

We report the observation of trielectronic recombination with simultaneous excitation of a K -shell and an L -shell electron, hence involving three active electrons. This process was identified in the x-ray emission spectrum of recombining highly charged Kr ions. An energy resolution three times h...

We demonstrate and theoretically analyze the dressing of several proximate Feshbach resonances in ⁸⁷Rb using radio-frequency (rf) radiation. We present accurate measurements and characterizations of the resonances, and the dramatic changes in scattering properties that can arise through the rf dre...

We propose the use of interaction-free quantum measurements with electrons to eliminate sample damage in electron microscopy. This might allow noninvasive molecular-resolution imaging. We show the possibility of such measurements in the presence of experimentally measured quantum decoherence rates a...

Electron emission spectra obtained by thermal collisions of He^∗(2¹S and 2³S ) atoms with Au(111) and Pt(111) surfaces were measured to clarify the electronically excited atom-metal interactions. It has been recognized that the metastable atoms de-excite on ordinary noble- and transition-metal s...

We propose a usage of microwave radiation in a magnetic trap for improving the cooling and trapping of cold antihydrogen atoms which are initially produced in high magnetic moment states. Inducing transitions toward lower magnetic moments near the turning points of the atom in the trap, followed by ...

We investigate harmonic generation from H₂⁺ molecules driven by intense few-cycle laser pulses whose linearly polarization axis makes an arbitrary angle χ with respect to the molecular axis. The H₂⁺ molecule is considered initially in various orbitals with nodal planes. It is found that a str...

We report a mode of dissociative ionization in an intense two-color laser field. When bond softened by the superposition of 800 and 400 nm ultrafast laser pulses in a narrow intensity range, H₂⁺ molecular ions experience ultraslow dissociation. This near-zero kinetic-energy release is supported by...

We present an optoelectrical cooling scheme for polar molecules based on a Sisyphus-type cooling cycle in suitably tailored electric trapping fields. Dissipation is provided by spontaneous vibrational decay in a closed level scheme found in symmetric-top rotors comprising six low-field-seeking rovib...

We propose methods to create fractional vortices in the cyclic state of an F=2 spinor Bose-Einstein condensate by manipulating its internal spin structure using pulsed microwave and laser fields. The stability of such vortices is studied as a function of the rotation frequency of the confining har...

We investigate the effect of the anisotropy between the s -wave scattering lengths of a three-component atomic Fermi gas loaded into a one-dimensional optical lattice. We find four different phases which support trionic instabilities made of bound states of three fermions. These phases distinguish ...

We have experimentally demonstrated a high level of control of the mode populations of guided-atom lasers (GALs) by showing that the entropies per particle of an optically GAL and the one of the trapped Bose-Einstein condensate (BEC) from which it has been produced are the same. The BEC is prepared ...

Correlations between particles can lead to subtle and sometimes counterintuitive phenomena. We analyze one such case, occurring during the sudden expansion of fermions in a lattice when the initial state has a strong admixture of double occupancies. We promote the notion of quantum distillation: dur...

We investigate the finite-temperature properties of attractive three-component (colors) fermionic atoms in optical lattices using a self-energy functional approach. As the strength of the attractive interaction increases in the low-temperature region, we observe a second-order transition from a Ferm...

We study the dynamics of the relative phase of a bilayer of two-dimensional superfluids after the two superfluids have been decoupled, using truncated Wigner approximation. On short time scales the relative phase shows “light-cone”-like thermalization and creates a metastable superfluid state, w...

We demonstrate experimentally and theoretically random-phase surface solitons in effectively instantaneous nonlinear media. The key mechanism for self-trapping is played by a nonlocal nature of the nonlinearity, in contrast to other incoherent solitons involving time averaging. These incoherent surf...

We demonstrate a chaotic microcavity laser whose quality is comparable to typical nonchaotic microcavity lasers, yet it has the unique characteristic of unidirectional output. The cavity shape is a disk with the boundary defined by a curve called limaçon of Pascal. For a lasing mode of volume less ...

We experimentally demonstrate that thermal radiation from a micron-sized dielectric particle depends sensitively on its size and shape through the cavity quantum-electrodynamic effect. Our laser trapping technique levitated a high-temperature microsphere of Al₂O₃ and enabled emission spectroscopy ...

We introduce a fundamental property of waveguides induced by the forces of the guided light, namely, the ability to self-align or be in instability. A nanoscale waveguide broken by an offset and a gap may tend to self-align to form a continuous waveguide. Conversely, depending on the geometry and li...

We demonstrate and characterize two coherent phenomena that can mitigate the effects of laser phase noise for electromagnetically induced transparency (EIT): a laser-power-broadening-resistant resonance in the transmitted intensity cross correlation between EIT optical fields, and a resonant suppres...

The amplification obtained using weak values is quantified through a detailed investigation of the signal-to-noise ratio for an optical beam-deflection measurement. We show that for a given deflection, input power and beam radius, the use of interferometric weak values allows one to obtain the optim...

We present soleakon: nonlinear self-trapped leaky modes displaying particlelike features. A “soleakon” forms when a wave function induces a potential barrier, whose resonant state (leaky mode) corresponds to the wave function itself. We show that, for a proper set of parameters, soleakons are ro...

We present an investigation of the coherent coupling of various transverse field modes of an optical cavity to ion Coulomb crystals. The obtained experimental results, which include the demonstration of identical collective coupling rates for different transverse modes of a cavity field to ions in t...

We introduce quantum spin models whose ground states allow for sizable entanglement between distant spins. We discuss how spin models with global end-to-end entanglement realize quantum teleportation channels with optimal compromise between scalability and resilience to thermal decoherence and can b...

In this paper, we present progress on the study of the symmetric extension criterion for separability. First, we show that a perturbation of order O(1/N) is sufficient and, in general, necessary to destroy the entanglement of any state admitting an N Bose-symmetric extension. On the other hand, ...

We calculate the quantum discord between two free modes of a scalar field, which start in a maximally entangled state and then undergo a relative constant acceleration. In a regime where there is no distillable entanglement due to the Unruh effect, we show that there is a finite amount of quantum di...

The necessary and sufficient conditions for minimization of the generalized rate error for discriminating among N pure qubit states are reformulated in terms of Bloch vectors representing the states. For the direct optimization problem, an algorithmic solution to these conditions is indicated. A s...

The goal of comparison is to reveal the difference of compared objects as fast and reliably as possible. In this paper we formulate and investigate the unambiguous comparison of unknown quantum measurements represented by nondegenerate sharp positive operator valued measures. We distinguish between ...

A generalized time-dependent perturbation theory is derived for superoperators. Instead of using the “standard” breakup of the Hamiltonian into a known zeroth order term and a correction, we use the approximate superpropagator to define the correction superoperator which is then used to obtain a...

Quantum fluctuations of an electromagnetic vacuum are investigated in a half-space bounded by a perfectly reflecting plate by introducing a probe described by a charged wave-packet distribution in time direction. The wave-packet distribution of the probe enables one to investigate the smearing effec...

From the local force equation of quantum mechanics and by expanding the interacting wave function in terms of the noninteracting Kohn-Sham wave function, we derive differential equations defining the local Hartree-exchange and the local correlation potential of density functional theory. The derived...

Recently, the O(α) and O(α³ ln α) radiative corrections to the orthopositronium lifetime have been presented in closed analytical form, in terms of basic irrational numbers that can be evaluated numerically to arbitrary precision [B. A. Kniehl, A. V. Kotikov, and O. L. Veretin, Phys. Rev....

We investigate the influence of atomic motion on precision Rabi spectroscopy of ultracold fermionic atoms confined in a deep one-dimensional optical lattice. We analyze the spectral components of longitudinal sideband spectra and present a model to extract information about the transverse motion and...

Differential, integral, and momentum-transfer cross sections for the elastic scattering of electrons by SiF₂ have been calculated for the incident electron energy range of 0–10 eV. These results are obtained by using the R -matrix method. The close-coupling expansion of the wave function of the...

We characterize the long-range dipolar scattering in two dimensions. We use the analytic zero energy wave function including the dipolar interaction; this solution yields universal dipolar scattering properties in the threshold regime. We also study the semiclassical dipolar scattering and find univ...

Target ionization and projectile charge changing were investigated for 20–500 keV/u C^q+ , O^q++He (q=1–3) collisions. Double- to single-ionization ratios R₂₁ of helium associated with no projectile charge change (direct ionization), single-electron capture, and single-electron loss were me...

Interactions of x-ray free-electron laser (XFEL) light with a single cluster target are numerically investigated by using a three-dimensional particle-in-cell code. The plasma dynamics as well as relevant atomic processes are taken into account, such as photoionization, the Auger effect, collisional...

We numerically investigate the dynamics of recollision of an electron in high-order harmonic generation (HHG) for an H atom and a molecular ion H₂⁺ using a short (ten optical cycles), and intense (I₀≥10¹⁴ W/cm²) , z -polarized linear laser pulse with wavelength 800 nm by accurately solving t...

The alignment-dependent nonsequential double ionization (NSDI) of diatomic molecule N₂ in intense fields is studied using the S -matrix theory. Our results show that the valence orbitals play an important role in alignment-dependent NSDI process: in addition to the contribution from the outmost ...

We investigate the scattering of intense laser radiation on free electrons using a semiclassical relativistic approach. The laser field is described as an ideal pulse with a finite duration, a fixed direction of propagation, and indefinitely extended in the plane perpendicular to it. This allows the...

We study the temperature dependence of optical properties of dilute gases of alkali-metal atoms in the state with Bose-Einstein condensates. The description is constructed in the framework of the microscopic approach that is based on the Green’s-functions formalism. We find the expressions for the...

A single down-spin fermion with an attractive zero-range interaction with a Fermi sea of up-spin fermions forms a polaronic quasiparticle. The associated quasiparticle weight vanishes beyond a critical strength of the attractive interaction, where a many-body bound state is formed. From a variationa...

We propose methods to create fractional vortices in the cyclic state of an F=2 spinor Bose-Einstein condensate by manipulating its internal spin structure using pulsed microwave and laser fields. The stability of such vortices is studied as a function of the rotation frequency of the confining har...

We investigate nonlinear Floquet states and quasienergies of a Bose-Einstein condensate in a double-well potential subject to a high-frequency driving field. A multiple time scale method is used to obtain the nonlinear Floquet states and quasienergies in both weak and strong nonlinearity regimes. It...

It has been known for some time that simple “optically bound” chains of dielectric microparticles can form in a counter propagating Gaussian beam optical trap. Here we report experimental observations of more complex trapped states, which do not reflect the underlying symmetry of the optical bea...

We study the influence of gain on negative refraction and super-resolution in transparent resonant metal-dielectric photonic band gap structures in the visible and near infrared ranges. We find that while the introduction of gain can compensate for losses caused by the excitation of surface waves, i...

The high power per mode of a recently developed 10 GHz femtosecond Ti:sapphire frequency comb permits nonlinear Doppler-free saturation spectroscopy in ⁸⁷Rb with a single mode of the comb. We use this access to the natural linewidth of the rubidium D₂ line to effectively stabilize the optical fr...

The pi-phase shift between |F=1, mF=0> and |F=2, mF=0> states for an adiabatic rotation of a magnetic field observed in Ramsey atom interferometry arises from the negative sign of the transition amplitude between the |1, 0> and |2, 0> states when the wave functions are rotated to the opposite direction. Using a two-photon Raman atom interferometer with a cold ensemble of sodium atoms, the phase shift for a half-rotation of the magnetic field was confirmed to be pi rad with an uncertainty of 4%, and the phase shift for a noncyclic adiabatic rotation of the magnetic field was investigated.

Spatial qudit states can be realized by using multi-slits to discretize the transverse momentum of a photon. The merit of this kind of spatial qudit states is that the implementation of higher dimensional qudits is relatively easy. As we have recently shown, the quantum states of these spatial qudits can be analyzed by scanning a single interference pattern. This method of single scan tomography can also be applied at higher dimensions, but the reconstruction becomes more sensitive to smaller details of the scanned patterns as the dimensions increase. In this paper, we investigate the effect of finite measurement resolution on the single scan tomography of spatial qutrits. Realistic measurement operators describing the spatial resolution of the measurement are introduced and the corresponding pattern functions for quantum state reconstruction are derived. We use the pattern functions to analyze experimental results for entangled pairs of spatial qutrits generated by spontaneous parametric down-conversion (SPDC). It is shown that a reliable reconstruction of the quantum state can be achieved with finite measurement resolution if this limitation of the measurement is included in the pattern functions of single scan tomography.

Arbitrary exponentially large unitaries cannot be implemented efficiently by quantum circuits. However, we show that quantum circuits can efficiently implement any unitary provided it has at most polynomially many nonzero entries in any row or column, and these entries are efficiently computable. One can formulate a model of computation based on the composition of sparse unitaries which includes the quantum Turing machine model, the quantum circuit model, anyonic models, permutational quantum computation, and discrete time quantum walks as special cases. Thus we obtain a simple unified proof that these models are all contained in BQP. Furthermore our general method for implementing sparse unitaries simplifies several existing quantum algorithms.

We develop a geometric approach to quantify the capability of creating entanglement for a general physical interaction acting on two qubits. We use the entanglement measure proposed by us for N-qubit pure states (Phys. Rev. A 77, 062334 (2008)). This geo- metric method has the distinct advantage that it gives the experimentally implementable criteria to ensure the optimal entanglement production rate without requiring a detailed knowledge of the state of the two qubit system. For the production of entanglement in practice, we need criteria for optimal entanglement production which can be checked in situ without any need to know the state, as experimentally finding out the state of a quantum system is generally a formidable task. Further, we use our method to quantify the entanglement capacity in higher level and multipartite systems. We quantify the en- tanglement capacity for two qutrits and find the maximal entanglement generation rate and the corresponding state for the general isotropic interaction between qutrits, using the entanglement measure of N-qudit pure states proposed by us (Phys. Rev. A 80, 042302 (2009)). Next we quantify the genuine three qubit entanglement capacity for a general interaction between qubits. We obtain the maximum entanglement generation rate and the corresponding three qubit state for a general isotropic interaction between qubits. The state maximizing the entanglement generation rate is of the GHZ class. To the best of our knowledge, the entanglement capacities for two qutrit and three qubit systems have not been reported earlier.

We report a prolonged coherence time of the collective spin wave of a thermal 87Rb atomic ensemble in a paraffin coated cell. The spin wave is prepared through a stimulated Raman process. The long coherence time is achieved by prolonging the lifetime of the spins with paraffin coating and minimize dephasing with optimal experimental configuration. The observation of the long time delayed-stimulated Stokes signal in the writing process suggests the prolonged lifetime of the prepared spins; a direct measurement of the decay of anti-Stokes signal in the reading process shows the coherence time is up to 300ms after minimizing dephasing. This is one hundred times longer than the reported coherence time in the similar experiments in thermal atomic ensembles based on the Duan-Lukin-Cirac-Zoller (DLCZ) and its improved protocols. This prolonged coherence time sets the upper limit of the memory time in quantum repeaters based on such protocols, which is crucial for the realization of long-distance quantum communication. The previous reported fluorescence background in the writing process due to collision in a sample cell with buffer gas is also reduced in a cell without buffer gas.

We generalize the recently proposed Greenberger-Horne-Zeilinger (GHZ) tripartite protocol [A. Galiautdinov, J. M. Martinis, Phys. Rev. A 78, 010305(R) (2008)] to fully connected networks of weakly coupled qubits interacting by way of anisotropic Heisenberg exchange g(XX+YY)+[g\tilde]ZZ. Our model adopted here differs from the more familiar Ising-Heisenberg chain in that here every qubit interacts with every other qubit in the circuit. The assumption of identical couplings on all qubit pairs allows an elegant proof of the protocol for arbitrary N. In order to further make contact with experiment, we study fidelity degradation due to coupling imperfections by numerically simulating the N=3 and N=4 cases. Our simulations indicate that the best fidelity at unequal couplings is achieved when (a) the system is initially prepared in the uniform superposition state (similarly to how it is done in the ideal case), and (b) the entangling time and the final rotations on each of the qubits are appropriately adjusted.

Entanglement swapping between photon pairs is a fundamental building block in schemes using quantum relays or quantum repeaters to overcome the range limits of long distance quantum key distribution. We develop a closed-form solution for the actual quantum states prepared by realistic entanglement swapping, which takes into account experimental deficiencies due to inefficient detectors, detector dark counts and multi-photon-pair contributions of parametric down conversion sources. We investigate how the entanglement present in the final state of the remaining modes is affected by the real-world imperfections. To test the predictions of our theory, comparison with previously published experimental entanglement swapping is provided. PACS numbers: 03.67.-a, 03.67.Bg, 03.67.Dd, 03.67.Hk, 42.50.Ex

Within an adiabatic approximation to the three-body Coulomb system, we study the strength of the leading order conformaly invariant attractive dipole interaction produced when a slow charged particle q3 (with mass m3) is captured by the first excited state of a dimer [with individual masses and charges (m1,q1) and (m2,q2=-q1)]. The approach leads to a universal mass-charge critical condition for the existence of three-body level condensation, (m1-1+m2-1)/[(m1+m2)-1+m3-1] > |q1/(24nbsp;nbsp;q3)|, as well as the ratio between the geometrically scaled energy levels. The resulting expressions can be relevant in the analysis of recent experimental setups with charged three-body systems, such as the interactions of excitons, or other matter-antimatter dimers, with a slow charged particle.

We have carried out a detailed and systematic study of the correlation energies of inert gas atoms Ne, Ar, Kr and Xe using relativistic many-body perturbation theory and relativistic coupled-cluster theory. In the relativistic coupled-cluster calculations, we implement perturbative triples and include these in the correlation energy calculations. We then calculate the dipole polarizability of the ground states using perturbed coupled-cluster theory.

Equilibrium mean charge states have been measured for 3 - 7 MeV lithium, boron, and carbon ions passing through thin carbon foils. The data are compared to the predictions of several semi-empirical models of charge equilibrium in the less than or equal 1MeV/u regime. The current work underscores the general problem of extrapolating models developed for high Z projectiles to ions of low Z. A compilation of experimental data for low Z ions in the low energy regime has been used to re-parameterize a few of the charge equilibrium models. Experimental techniques, comments and suggestions on the nature of the equilibrium charge states of low Z ions are presented.

A characteristic dependence of the proton-induced 2s subshell ionization cross-section generated by the nodal structure of the 2s wave function was probed via high-resolution measurements of the L Beta 3 (L1-M3) and L Beta 6 (L3-N1) x-ray lines of Ag. The intensity ratio of the measured lines depends strongly on the proton energy exhibiting a pronounced maximum around 0.4 MeV. The experimental intensities are critically compared to the theoretically predicted values. The latter were obtained using the ionization cross sections calculated within the semiclassical approximation employing hydrogen-like and Dirac-Fock electron wave functions.

Three-body recombination in helium-helium-alkali collisions at cold temperatures is studied using the adiabatic hyperspherical representation. The rates for the three-body recombination processes 4He+4He+X4He+4HeX and 4He+4He+X4He2+X, with X=7Li, 23Na, 39K, 85Rb and 133Cs, are calculated at nonzero collision energies by including not only zero total angular momentum, J=0, states but also J > 0 states. The three-body recombination rates show a relatively weak dependence on the alkali species, differing from each other only by about one order of magnitude, except for the 4He-4He-23Na system.

The electron dynamics in pnbsp;-nbsp;He and He2+nbsp;-nbsp;He collisions have been investigated on the level of the independent electron model by using the two-center basis generator method. Projectile angular-differential cross sections for various one- and two-electron processes involving electron transfer have been calculated with the eikonal approximation. Overall, the calculated cross sections are in good agreement with the most recent experimental cold target recoil ion momentum spectroscopy data taken at impact energies in the range from 40 to 630 keV/amu. This demonstrates, somewhat surprisingly, that electron correlations play but a minor role for the processes and the energies considered.

The pressure broadening and shift rates for the cesium D1 (62P1/2 62S1/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4 and 3He were obtained for pressures less than 300 torr at temperatures under 65C by means of laser absorption spectroscopy. The collisional broadening rate, gL, for He, Ne, Ar, Kr, Xe, N2, H2, HD, D2, CH4, C2H6, CF4, and 3He are 24.13, 10.85, 18.31, 17.82, 19.74, 16.64, 20.81, 20.06, 18.04, 29.00, 26.70, 18.84, and 26.00 MHz/torr, respectively. The corresponding pressure induced shift rates, d, are 4.24, -1.60, -6.47, -5.46, -6.43, -7.76, 1.11, 0.47, 0.00, -9.28, -8.54, -6.06, and 6.01 MHz/torr. These rates have then been utilized to calculate Leonard-Jones potential coefficients to quantify the interatomic potential surfaces. The broadening cross-section has also been shown to correlate with the polarizability of the collision partner.

We report improved precision measurements of the Van der Waals potential strength (C3) for Na atoms and a silicon-nitride (SiNx) surface. We studied diffraction from nano-fabricated gratings with a particular "magic" open-fraction that allows us to determine C3 without the need for separate measurements of the width of the grating openings. Therefore, finding the magic open-fraction improves the precision of C3 measurements. The same effect is demonstrated for a grating with an arbitrary open-fraction by rotating it to a particular "magic" angle, yielding C3=3.420.19 eV \mathringA3 for Na and a SiNx surface. This precision is sufficient to detect a change in C3 due to a thin metal coating on the grating surface. We discuss the contribution to C3 of core electrons and edge effects.

We demonstrate experimentally the efficient fusion neutron generation from Coulomb explosion (CE) of laser irradiated large-size heteronuclear deuterated methane clusters. A conversion efficiency of 2.1times;106 neutrons per joule of incident laser energy is obtained with a 120-mJ, 70-fs laser pulse. It is 50 times higher than that of homonuclear deuterium clusters of similar size. This enhancement is attributed to the significant increase in the deuteron kinetic energies by 4 folds due to energetic boosting and overrun effects during CE of heteronuclear clusters. The yield of 5.5times;106 neutrons per pulse is obtained with a 100-TW 50-fs driving laser pulse at an intensity of 1.5times;1019W/cm2. This work may facilitate the development of a high-flux table-top neutron source.

We show the existence of a permanent molecular planar alignment in field-free conditions. We present different control strategies using shaped laser pulses to reach this state. The strategies are robust with respect to the temperature and can be implemented with the state of the art technology. They can be applied to linear molecules but also to symmetric or asymmetric top molecules along the most polarizable molecular axis. We propose potential applications of this planar alignment such as the increase of the adsorption on a surface.

We present a novel approach to calculating strong field ionization dynamics of multielectron molecular targets. Adopting a multielectron wavefunction ansatz based on field-free ab initio neutral and ionic multielectron states, a set of coupled time-dependent single-particle Schr#246;dinger equations describing the neutral amplitude and continuum electron are constructed. These equations, amenable to direct numerical solution or further analytical treatment, allow one to study multielectron effects during strong field ionization, recollision, and high harmonic generation. We apply the method to strong field ionization of CO2, and suggest the importance of intermediate core excitation to explain previous failure of analytical models to reproduce experimental ionization yields for this molecule.

We present a calculation of the spectral functions and the associated rf response of ultracold fermionic atoms near a Feshbach resonance. The single particle spectra are peaked at energies that can be modeled by a modified BCS dispersion. However, even at very low temperatures their width is comparable to their energy, except for a small region around the dispersion minimum. The structure of the excitation spectrum of the unitary gas at infinite scattering length agrees with recent momentum-resolved rf spectra near the critical temperature. A detailed comparison is made with momentum integrated, locally resolved rf spectra of the unitary gas at arbitrary temperatures and shows very good agreement between theory and experiment. The pair size defined from the width of these spectra is found to coincide with that obtained from the leading gradient corrections to the effective field theory of the superfluid.

We derive a generalized Gross-Pitaevskii density-functional equation appropriate to study the Bose-Einstein condensate (BEC) of dimers formed of singlet spin-half Fermi pairs in the BEC-unitarity crossover while the dimer-dimer scattering length a changes from 0 to . Using an effective one-dimensional form of this equation, we study the phenomenon of dynamical self-trapping of a cigar-shaped Fermi super-fluid in the entire BEC-unitarity crossover in a double-well potential. A simple two-mode model is constructed to provide analytical insights. We also discuss the consequence of our study on the self-trapping of an atomic BEC in a double-well potential.

We present the full evaluation of a cold atom gyroscope based on atom interferometry. We have performed extensive studies to determine the systematic errors, scale factor and sensitivity. We demonstrate that the acceleration noise can be efficiently removed from the rotation signal, allowing us to reach the fundamental limit of the quantum projection noise for short term measurements. The technical limits to the long term sensitivity and accuracy have been identified, clearing the way for the next generation of ultra-sensitive atom gyroscopes.

This paper reports improved reconstruction of complex wavefields from extended objects. The combination of ptychography with Fresnel diffractive imaging results in better reconstructions with fewer iterations required to convergence than either method considered separately. The method is applied to retrieve the projected thickness of a gold micro-structure and comparative results using ptychography and Fresnel diffractive imaging are presented.

We report our experimental observations of spatial shift and splitting of four-wave mixing (FWM) signal beams induced by additional dressing laser beams. These effects are caused by the enhanced cross-Kerr nonlinearity due to atomic coherence in a two-level atomic system. The spatial separation and number of the split FWM beams can both be controlled by the intensity of the dressing beam, the Kerr nonlinearity, and atomic density. Theoretical results agree quite well with the observations. Studies of such controlled beam splitting can be very useful in understanding spatial soliton formation and interactions, and in applications for spatial signal processing.

We study the field generated in the outer space by the superposition of modes of a regular circular monomode fiber array. It is shown that a supermode of the fiber array generates a discrete optical vortex; the formula for the topological charge of the vortex is obtained depending on the order of the supermode and the number of fibers in the array. The orbital angular momentum carried by an arbitrary superposition of supermodes is shown to equal the weighted sum of partial angular momenta of supermodes. It is shown that for certain combinations of supermodes the angular momentum comprises along with its intrinsic part also the extrinsic constituent. For such combinations precession of the angular momentum about the propagation axis is demonstrated. It is demonstrated that by combining supermodes one can generate in the array stable regularly rotating linear azimuthons. By creating a phased excitation of certain groups of fibers in the array one can control the global soliton-like motion of the excited domain.

We report experimental observation of slow/fast light in configuration of counter-propagating saturating and probe waves in erbium-doped fibers with saturable absorption. The delayed/accelerated probe light propagation is shown to be associated with two-wave mixing between these two waves via dynamic population grating. As compared with recording at 1526 nm from the central region of Er+3 fundamental absorption spectrum, at 1485 nm the population grating has significant admixture of the refractive index component. This results in a significant asymmetry of the TWM induced transmittance of the probe wave as a function of the frequency off-set Delta Omega between the waves and shifts position of the maximum group delay from zero Delta Omega. The same reason ensures appearance of a significant group advancement for the frequency offset of the opposite sign.