Physical Review A

The π -phase shift between |F=1,m_F=0⟩ and |F=2,m_F=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 o...

The interaction energy due to electromagnetic field fluctuations between two infinitely long straight parallel dielectric-diamagnetic cylinders immersed in a medium is considered. We make use of the mode summation method for the calculations. We investigate the energy dependence on the cylindrical r...

We determine the conditions under which topological order survives a rapid quantum quench. Specifically, we consider the case where a quantum spin system is prepared in the ground state of the toric code model and, after the quench, it evolves with a Hamiltonian that does not support topological ord...

We present a system for the simulation of quantum phase transitions of collective internal qubit and phononic states with a linear crystal of trapped ions. The laser-ion interaction creates an energy gap in the excitation spectrum, which induces an effective phonon-phonon repulsion and a Jaynes-Cumm...

We demonstrate a quadratic phase gate for one-way quantum computation in the continuous-variable regime. This canonical gate, together with phase-space displacements and Fourier rotations, completes the set of universal gates for realizing any single-mode Gaussian transformation such as arbitrary sq...

Isolated nuclear spins provide a promising building block for quantum information science, motivating development of techniques to characterize, control, and detect them in suitable systems. Working with the nitrogen-vacancy center in diamond, we demonstrate robust initialization, manipulation, and ...

Recently, the molecular cation PtH⁺ was suggested as a promising candidate for the experimental search for the electron electric dipole moment. For estimating the sensitivity of the experiment on the cation and for interpretation of the experimental results, it is necessary to calculate an effecti...

A high-resolution (ΔE∼55 meV) trap-based positron beam has been used to measure absolute scattering cross sections for the excitation of the resolved 2 ¹S,P states of helium at energies between threshold and 38 eV. The experimental integral cross sections, which have typical uncertainties...

A quantum-mechanical approach to ion-molecule collisions is presented. It involves a separation of molecular geometry and collision dynamics and enables the use of the basis generator method developed for ion-atom collisions with relatively minor modifications. As a first application, we consider th...

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 2.1×10⁶ neutrons/J of incident laser energy is obtained with a 120 mJ, 70 fs laser pulse. It is ...

A method for complete characterization of the waveform of individual few-cycle laser pulses is presented. By analyzing the “left” and “right” asymmetries of high-energy photoelectrons along the polarization axis using the recently developed quantitative rescattering theory, we show that the ...

We derive the two-channel (TC) description of the photoassociation (PA) process in the presence of a magnetic Feshbach resonance and compare to full coupled multichannel calculations for the scattering of ⁶Li-⁸⁷Rb . Starting from a similar approach as that of Pellegrini [Phys. Rev. Lett. 101, 0532...

The Auger transitions to different repulsive doubly charged molecular ion states are separated by measuring the angular resolved photoelectrons and Auger electrons in coincidence in the molecular fixed frame. The separation is achieved by comparing the experimental Auger-electron angular distributio...

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...

We analyzed the discrepancy of the angular dependence of strong-field ionization for CO₂ among the different theoretical calculations and experiments. Using a more accurate ground-state wave function of CO₂ in the asymptotic region, we showed that the accuracy in the earlier tunneling ionization...

We study the interplay of quantum statistics, strong interactions, and finite temperatures in the two-component (spinor) Bose gas with repulsive delta-function interactions in one dimension. Using the Thermodynamic Bethe Ansatz, we obtain the equation of state, population densities, and local densit...

Recently demonstrated superconducting atom chips provide a platform for trapping atoms and coupling them to solid-state quantum systems. Controlling these devices requires a full understanding of the supercurrent distribution in the trapping structures. For type-II superconductors, this distribution...

We demonstrate a two-dimensional atom interferometer in a harmonic magnetic waveguide using a Bose-Einstein condensate. Such an interferometer could measure rotation using the Sagnac effect. Compared to free space interferometers, larger interactions times and enclosed areas can in principle be achi...

Dispersive shock waves (DSWs) are studied theoretically in the context of two-dimensional (2D) supersonic flow of a superfluid. Employing Whitham averaging theory for the repulsive Gross-Pitaevskii (GP) equation, suitable jump and entropy conditions are obtained for an oblique DSW, a fundamental bui...

It is shown that the jump in the momentum distribution of Fermi gases evolves smoothly for small and intermediate times once an interaction between the fermions is suddenly switched on. The jump does not vanish abruptly. The loci in momentum space where the jumps occur are those of the noninteractin...

Whether a spin-1/2 Fermi gas will become ferromagnetic as the strength of repulsive interaction increases is a long-standing controversial issue. Recently this problem has been studied experimentally by Jo [Science 325, 1521 (2009)] in which the authors claim a ferromagnetic transition is observed....

We propose to implement a sub-shot-noise matter-wave interferometer via the stimulated dissociation of a molecular Bose-Einstein condensate and study the collisional loss of atom-molecule coherence during its phase-acquisition time. The obtained n -atom states are two-atom [SU(1,1)] coherent states...

We present a numerical study of quantum turbulence within the three-dimensional Gross-Pitaevskii equation, concentrating on the direct energy cascade in the case of a forced-dissipated system. We show that the behavior of the system is very sensitive to the properties of the model at the scales grea...

Dispersion and dissipation are inherent to electromagnetic wave propagation in metamaterials. We show that these inherent limitations can be overcome by a self-induced transparency pulse that stably propagates through a metamaterial sparsely doped with resonantly absorbing dopants. This pulse has th...

We show that when an electron or photon propagates in a cylindrically symmetric waveguide, its spin angular momentum (SAM) and its orbital angular momentum (OAM) interact. Remarkably, we find that the dynamics resulting from this spin-orbit interaction are quantitatively described by a single expres...

An exact solution for the problem of interaction between whispering gallery modes of spherical microresonators and a single dipole is presented. It is predicted that experimentally observed spectral doublets associated with this interaction are a part of a triplet whose third component has yet to be...

We report a unified representation of the spatial and angular Goos-Hänchen and Imbert-Fedorov shifts that occur when a light beam reflects from a plane interface. We thus reveal the dual nature of spatial and angular shifts in optical beam reflection. In the Goos-Hänchen case we show theoretically...

The Raman gain of a probe light in a three-state Λ scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit simultaneously occurring narrow...

We suggest possibilities for manipulation and ground-state cooling of micromechanical oscillators by resonant coupling of the mirror vibrations to narrow optical transitions of a designed material ensemble within a cavity mode. Particles, modeled as a two-level ensemble, create intracavity narrow ba...

We present an approach to explore and control nonlinear interactions between two orthogonally polarized femtosecond filaments launched parallel in air. The self-phase and cross-phase modulations due to the Kerr effect and cross-(de)focusing induced by the plasma and molecular alignment were distinct...

We study the interplay of quantum statistics, strong interactions, and finite temperatures in the two-component (spinor) Bose gas with repulsive delta-function interactions in one dimension. Using the Thermodynamic Bethe Ansatz, we obtain the equation of state, population densities, and local densit...

We investigate two-component ultracold fermions loaded into a decorated square lattice, which are described by the Hubbard model with repulsive interactions and nearest-neighbor hoppings. By combining the real-space dynamical mean-field theory with the numerical renormalization-group method, we disc...

In this addendum to our paper [B. Van Schaeybroeck, Phys. Rev. A 78, 023624 (2008)] we present an exact solution of the interface tension of Bose-Einstein condensates in a particular parameter regime.

We present a fundamental concept—closed sets of correlations—for studying nonlocal correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more generally to consistent physical theories, must be closed under a natural set of operations. Hence, study...

The resources required to solve the general interacting quantum N -body problem scale exponentially with N , making the solution of this problem very difficult when N is large. In a previous series of papers we develop an approach for a fully interacting wave function for a confined system of id...

Using a dynamical quantum Zeno effect, we propose a general approach to control the coupling between a two-level system (TLS) and its surroundings, by modulating the energy-level spacing of the TLS with a high-frequency signal. We show that the TLS-surroundings interaction can be turned off when the...

Exact quantum master equation is derived for dephasing of a two-level system, which is an homogeneous time-convolutionless equation even though there is an initial correlation between a two-level system and a thermal reservoir. The result is compared with the quantum master equation derived by means...

The only information available about an alleged source of entangled quantum states is the amount S by which the Clauser-Horne-Shimony-Holt inequality is violated: nothing is known about the nature of the system or the measurements that are performed. We discuss how the quality of the source can be...

We investigate the connection between local minima in the problem Hamiltonian and first-order quantum phase transitions during adiabatic quantum computation. We demonstrate how some properties of the local minima can lead to an extremely small gap that is exponentially sensitive to the Hamiltonian p...

The energies, fine-structure splittings, Auger channel energies, and the Auger widths of the high-lying triply excited 2l2l^′nl^″ (n≥2) states of ²S , ²D , and ²P^o resonances for Be⁺ are studied using the saddle-point variational method and saddle-point complex-rotation method. The rel...

We develop a determinantal method in a quantum scattering system for direct evaluation of various quantities including the local field amplitude and transition amplitude ( S -matrix element). This method is applicable to multichannel elastic and inelastic scattering systems without rearranging the p...

Recent experiments on collision processes of O⁷⁺ and 6+ ions colliding with methane at the same velocity show unexpected differences in the fragmentation cross sections of the methane. Despite the expected similarity of these two processes, as both projectiles are hydrogenic, the mechanisms of ...

We demonstrate an atom detector based on field ionization and subsequent ion counting. We make use of field enhancement near tips of carbon nanotubes to reach extreme electrostatic field values of up to 9×10⁹ V/m , which ionize ground-state rubidium atoms. The detector is based on a carpet of mu...

Population transfer to the excited electronic state E ¹Σ_g of Li₂ by transform limited delayed femtosecond pulses has been investigated. The validity of the usual neglect of some field-molecule coupling terms in such transfers, accomplished using counterintuitively ordered pulses through “ad...

Motivated by the recent discovery that a reflecting wall moving with a square-root-in-time trajectory behaves as a universal stopper of classical particles regardless of their initial velocities, we compare linear-in-time and square-root-in-time expansions of a box to achieve efficient atom cooling....

We report on a teleportation scheme, in which a controllable orbital angular momentum (OAM) generator is teleported. Via our scheme, Alice is able to—according to another independent photon’s spin state (polarization) sent by Carol—electrically control the remote OAM generation on Bob’s phot...

We report on the experimental observation of two-dimensional surface solitons residing at the interface between a homogeneous square lattice and a superlattice that consists of alternating “deep” and “shallow” waveguides. By exciting single waveguides in the first row of the superlattice, we...

Several wave-function approximations describing spontaneous parametric down-conversion can be found in the literature. Basically all cases are derived from the standard Hamiltonian for parametric down-conversion. Most frequently, particular cases describing collinear or paraxial approximations are d...

We report electromagnetically induced gain in a highly degenerate two-level rotational vibrational molecular system. Using two photon (Raman-type) interaction with right and left circularly polarized pump and probe waves, the Zeeman coherence is established within the manifold of degenerate sublevel...

We report on the linear and nonlinear optical response of metamaterials evoked by first- and second-order multipoles. The analytical ground on which our approach is based permits for new insights into the functionality of metamaterials. For the sake of clarity we focus here on a key geometry, namely...

We study the dynamic sensitivity of an atomic ensemble dressed by a single-mode cavity field (called a photon-dressed atomic ensemble), which is described by the Dicke model near the quantum critical point. It is shown that when an extra atom in a pure initial state passes through the cavity, the ph...

In a self-defocusing optical cavity, optical-field perturbations on a vortex background behave as sound waves in a (2+1) rotating acoustic black-hole spacetime. Numerical integration of the associated Klein-Gordon equation using typical experimental parameters shows that optical perturbations in t...

In order to characterize the statistical aspect of the energy loss in particle penetration, Bohr developed a kinetic theory and applied it to a beam of fast α particles interacting with free electrons. The present study rests on this classical theory of collisional straggling, and it is implement...

Diffraction patterns produced by grazing scattering of fast atoms from insulator surfaces are used to examine the atom-surface interaction. The method is applied to He atoms colliding with a LiF(001) surface along axial crystallographic channels. The projectile-surface potential is obtained from an ...

We have earlier constructed a generalized entropy concept to show the direction of time in an evolution following from a Markov generator. In such a dynamical system, the entity found changes in a monotonic way starting from any initial state of the system. In this paper, we generalize the treatment to the case when population is pumped into the system from levels not explicitly considered. These populations then pass through the coupled levels and exit by decay to levels outside the system. We derive the form of the equation of motion and relate it to our earlier treatments. It turns out that the formalism can be generalized to the new situation. Its physically relevant features are demonstrated, and the behaviour obtained is illustrated by numerical treatment of the standard two-level system with pumping and relaxation included.

It has become common practice to model large spin ensembles as an effective pseudospin with total angular momentum J=Ntimes;j, where j is the spin per particle. Such approaches (at least implicitly) restrict the quantum state of the ensemble to the so-called symmetric Hilbert space. Here, we argue that symmetric states are not generally well-preserved under the type of decoherence typical of experiments involving large clouds of atoms or ions. In particular, symmetric states are rapidly degraded under models of decoherence that act identically but locally on the different members of the ensemble. Using an approach [Phys.nbsp;Rev.nbsp;A 78, 052101 (2008)] that is not limited to the symmetric Hilbert space, we explore potential pitfalls in the design and interpretation of experiments on spin-squeezing and collective atomic phenomena when the properties of the symmetric states are extended to systems where they do not apply.

Almost all Bell-inequality experiments to date have used postselection, and therefore relied on the fair sampling assumption for their interpretation. The standard form of the fair sampling assumption is that the loss is independent of the measurement settings, so the ensemble of detected systems provides a fair statistical sample of the total ensemble. This is often assumed to be needed to interpret Bell inequality experiments as ruling out hidden-variable theories. Here we show that it is not necessary; the loss can depend on measurement settings, provided the detection efficiency factories as a function of the measurement settings and any hidden variable. This condition implies that Tsirelson's bound must be satisfied for entangled states. On the other hand, we show that it is possible for Tsirelson's bound to be violated while the CHSH-Bell inequality still holds for unentangled states, and present an experimentally feasible example.

We study the relationship between entanglement and parametric resonance in a system of two coupled time-dependent oscillators. As a measure of bipartite entanglement, we calculate the linear entropy for the reduced density operator, from which we study the entanglement dynamics. In particular, we find that the bipartite entanglement increases in time up to a maximal mixing scenario, when the set of auxiliary dynamical parameters are under parametric resonance. Moreover, we obtain a closed relationship between the correlations in the ground state, the localisation of the Wigner function in phase space, and the localisation of the wave function of the total system.

For quantum states of two subsystems, highly entangled states have higher capacity of transmitting classical as well as quantum information, and viceversa. We show that this is no more the case in general: quantum capacities of multi-access channels, motivated by communication in quantum networks, do not have any relation with genuine multiparty entanglement measures. Importantly, the statement is demonstrated for arbitrary multipartite entanglement measures. Along with revealing the structural richness of multi-access channels, this gives us a tool to classify multiparty quantum states from the perspective of its usefulness in quantum networks, which cannot be visualized by any genuine multiparty entanglement measure.

We study the error threshold of topological color codes on Union Jack lattices that allow for the full implementation of the whole Clifford group of quantum gates. After mapping the error-correction process onto a statistical mechanical random 3-body Ising model on a Union Jack lattice, we compute its phase diagram in the temperature-disorder plane using Monte Carlo simulations. Surprisingly, topological color codes on Union Jack lattices have a similar error stability to color codes on triangular lattices, as well as to the Kitaev toric code. The enhanced computational capabilities of the topological color codes on Union Jack lattices with respect to triangular lattices and the toric code combined with the inherent robustness of this implementation show good prospects for future stable quantum computer implementations.

A parity measurement on two qubits, each consisting of a single atom in a cavity, can be realized by measuring the phase shift of a probe beam, which interacts sequentially with the two qubits, but imperfections lead to decoherence within the subspaces of a given parity. We demonstrate that a different setup, where the probe light interacts repeatedly with the qubits, can reduce the rate of decoherence within the odd or the even parity subspace significantly. We consider both the case of a resonant and the case of a nonresonant light-atom interaction and find that the performance is comparable if the parameters are chosen appropriately.

We present a formalism for rigorous multichannel scattering calculations of cross sections for inelastic collisions of atoms and molecules confined in 1D optical lattices. We obtain analytical expressions for the mean frequency of inelastic collisions in a confined gas in the temperature regime T ~ (h/2p) w and at temperatures T >> (h/2p) w, where w is the oscillation frequency of trapped particles in the confining potential. Our numerical calculations for the gaseous mixture of Li and Rb atoms show that inelastic collisions in the temperature regime T ~ (h/2p) w exhibit a deviation from 3D scattering. This deviation is more significant for systems with stronger confinement and larger scattering lengths. We find that the ratios of rate constants for inelastic scattering and elastic collisions are suppressed in confined gases at T ~ (h/2p) w and this suppression is significant for Li-Rb collisions at T < 40nbsp;mK.

A theoretical treatment of charge transfer processes induced by collision of phosphorus P3+(3s2)1S ions on atomic hydrogen and helium has been carried out using ab-initio potential energy curves and couplings at the multi-reference configuration interaction level of theory. The cross-sections calculated by means of semi-classical collision methods show the existence of a significant charge transfer in the [0.1-700] keV laboratory energy range. Radial and rotational coupling interactions are analysed for both collision systems.

We report a collision-induced Raman band by room-temperature gas mixtures of sulfur hexafluoride and nitrogen. The band is centered at the sum of the frequencies of the symmetric-stretching n1 transition of SF6 and the fundamental transition of N2, and its intensity scales as the product of the partial densities of the gases. The observed process is first evidence of double incoherent Raman scattering (DRS) by SF6 -N2, in which both molecules simultaneously undergo two Raman-allowed transitions. The band was found to be fully depolarized, in agreement with previous observations in other systems and with theoretical predictions. Its intensity is about one-third higher than the total area predicted by the leading-order dipole-induced dipole model. This discrepancy suggests DRS as a practical means of assessing the quality of intermolecular potential models, which in the case of SF6 -N2 is believed still to be not good enough. Our work is expected to open the door to a multitude of studies involving complicated processes encountered in nonpolar gases and their mixtures, which are of direct relevance to atmospheric research.

We study the dynamics of a supersonic molecular beam in a low finesse optical cavity and demonstrate that most molecules in the beam can be decelerated to zero central velocity by the intracavity optical field in a process analogous to electrostatic Stark deceleration. We show that the rapid switching of the optical field for slowing the molecule is automatically generated by the cavity-induced dynamics. We further show that ~1% of the molecules can be optically trapped at a few milliKelvin in the same cavity.

We investigate multiphoton ionization of hydrogen molecular ions in a 480 nm intense laser field solving the time-dependent Schr#246;dinger equation numerically in prolate spheroidal coordinates. We descritize space on a generalized pseudospectral grid and propagate the electronic wavefunction using a second-order-split operator method. By including and excluding the 2psu state in the basis expansion, we confirm that the observed 10 eV peak in the recent experiment [Litvinyuk et al., New J. of Phys. 10, 083011 (2008). ] comes from the enhanced ionization via three-photon resonant excitation of the molecular ions. Folding our calculated ionization rates with the vibrational density distribution, we obtain the kinetic energy release spectra, which are in reasonable agreement with the experimental measurement. Furthermore, using this enhanced ionization, we suggest a pump-probe experiment to trace the vibrational wavepacket.

Two coupled BECs with a large population imbalance exhibit macroscopic quantum self-trapping (MQST) if the ratio of interaction energy to tunneling energy is above a critical value. Here we investigate effect of quantum fluctuations on MQST. In particular, we analyze the dynamics of a system of two elongated Bose gases prepared with a large population imbalance, where due to the quasi one dimensional character of the gas we no longer have true long range order, and the effect of quantum fluctuations is much more important. We show that MQST is possible in this system, but even when it is achieved it is not always dynamically stable. Using this instability one can construct states with sharply peaked momentum distributions around characteristic momenta dependent on system parameters. Our other finding is the nonmonotonic oscillating dependence of the decay rate of the MQST on the length of the wires. We also address the interesting question of thermalization in this system and show that it occurs only in sufficiently long wires.

Bloch band and stabilities of Bloch waves of superfluid Fermi gases in one-dimensional (1D) periodic optical lattices are discussed. Within the hydrodynamical theory and the two-mode approximation, the Bloch band structure, the energetic and dynamical instabilities of Bloch waves at the first Brilliouin zone are presented. The results show that, when the atom density beyond a critical value, a loop structure in Bloch band at the zone edge is developed along the BEC-BCS crossover. The Bloch band structure and the stabilities of Bloch waves are modified dramatically when the system crosses from the BEC side to the BCS side, and can be adjusted to the required characteristics by changing the atoms interaction (with Feshbach resonance technique), the atom density and the lattice parameters. The analytical expressions of the critical atom density for exciting the loop structure and maintaining the stabilities of Bloch waves are obtained.

We analyze the repulsive fermionic Hubbard model on square and cubic lattices with spin imbalance and in the presence of a parabolic confinement. We analyze the magnetic structure as a function of the repulsive interaction strength and polarization. In the first part of the paper we perform unrestricted Hartree-Fock calculations for the 2D case and find that above a critical interaction strength Uc the system turns ferromagnetic at the edge of the trap, in agreement with the ferromagnetic Stoner instability of a homogeneous system away from half-filling. For U < Uc we find a canted antiferromagnetic structure in the Mott region in the center and a partially polarized compressible edge. The antiferromagnetic order in the Mott plateau is perpendicular to the direction of the imbalance. In this regime the same qualitative behavior is expected for 2D and 3D systems. In the second part of the paper we give a general discussion of magnetic structures above Uc. We argue that spin conservation leads to nontrivial textures, both in the ferromagnetic polarization at the edge and for the Neel order in the Mott plateau. We discuss differences in magnetic structures for 2D and 3D cases.

We studied the static and dynamic domain wall solutions of spinor Bose-Einstein condensates trapped in an optical lattice. The single and double domain wall solutions are constructed analytically. Our results show that the magnetic field and light-induced dipolar interactions play an important role for both the formation of different domain walls and the adjusting of domain wall width and velocity. Moreover, these interactions can drive the motion of domain wall of Bose ferromagnet systems similar to that driven by the external magnetic field or the spin-polarized current in fermion ferromagnet.

All experiments with ultracold atoms are performed in the presence of background residual gas. With the help of a suitable master equation we investigate a role of these fast atoms on the loss of coherence in optical lattices. We present an exact solution of the master equation and give the analytic formulas for all correlation functions in the presence of one body losses. Additionally we discuss existing of a Schr#246;dinger cat state predicted in this system in .

Ultracold atoms whose de Broglie wavelength is of the same order as an extended confining potential can experience waveguiding along the potential. When the transverse kinetic energy of the atoms is sufficiently low, they can be guided in the lowest order mode of the confining potential by analogy with light guided by a single mode optical fibre. We have obtained the first images of the transverse mode structure of guided matter waves in a confining potential with up to 65% of atoms in the lowest order mode. The coherence of the guided atomic de Broglie waves is demonstrated by the diffraction pattern produced when incident upon a two dimensional periodic structure. Such coherent waveguides will be important atom optic components in devices with applications such as atom holography and atom interferometry.

We propose a time-dependent three-dimensional numerical model where iron impurities and polarons are both considered as photoactive centers to explain beam self-trapping in biased lithium niobate crystal. It shows that the intensity dependent behavior reported experimentally is due to the competition between the drift current and the nonlinear photovoltaic current. For low light intensity beam self-focusing occurs while beam-splitting is observed at higher intensity level.

We discuss a scheme for measuring N-th order coherences of two orthogonally polarized light fields in a single spatial mode at very limited experimental costs. For this, we only need to measure N-th order intensity moments after the light beam has passed through two quarter-wave plates, one half-wave plate, and a polarizing beam splitter for specific settings of the wave plates. We show that this method can be applied for arbitrarily large N and give a set of explicit values for the settings of the wave plates, constituting an optimal measurement of the N-th order coherences for any N. For Fock states the method introduced here corresponds to a full state tomography. Applications of the scheme to systems other than polarization optics are discussed.

We study the compression of strong x-ray pulses from x-ray free-electron lasers propagating through the resonant medium of atomic argon. The simulations are based on the three-level model with the frequency of the incident x-ray pulse tuned in the 2p3/2-4s resonance. The pulse propagation is accompanied by the self-seeded stimulated resonant Raman scattering (SRRS). The SRRS starts from two channels of amplified spontaneous emission (ASE), 4s- 2p3/2 and 3s- 2p3/2, which form the extensive ringing pattern and widen the power spectrum. The produced seed field triggers the Stokes ASE channel 3s- 2p3/2. The population inversion is quenched for longer propagation distances where the ASE is followed by the lasing without inversion (LWI) which amplifies the Stokes component. Both ASE and LWI reshape the input pulse: the compressed front part of the pulse (up to 100 as) is followed by the long tail of the ringing and beating between the pump and Stokes frequencies. The pump pulse also generates weaker Stokes and anti-Stokes fields caused by four-wave mixing. These four spectral bands have fine structures caused by the dynamical Stark effect. A slowdown of the XFEL pulse up to 78% of the speed of light in vacuum is found because of large nonlinear refractive index.

The aim of this paper is to extend linear quantum dynamical network theory to include static Bogoliubov components (such as squeezers). Within this integrated quantum network theory we provide general methods for cascade or series connections, as well as feedback interconnections using linear fractional transformations. In addition, we define input-output maps and transfer functions for representing components and describing convergence. We also discuss the underlying group structure in this theory arising from series interconnection. Several examples illustrate the theory.

We address quantum interference of Zeeman atom embedded in two kinds of structures containing left-handed materials (LHM), which are single LHM layer mounted on single mirror (SLSM) and Fabry-Perot cavity filled with LHM layer by half (FPCLH). Especially, the influence of the dissipation of LHM on quantum interference has been studied in detail. Though dissipation weakens quantum interference in general, it holds nearly complete quantum interference when the thickness of cavity is small for FPCLH. Moreover, with equivalence of left- and right- rotation polarized dipoles to two spatial orthogonal dipoles, we found the optimum orientation of two orthogonal dipoles which can realize the maximum quantum interference in certain anisotropic environment. Our research may have potential applications in the designing of micro-size devices.

We investigate the possibility of using a hybrid CARS technique for non-invasive monitoring of blood glucose levels. Our technique combines instantaneous coherent excitation of several characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the non-resonant four-wave-mixing background while maximizing the Raman-resonant signal, and allows rapid and highly specific detection even in the presence of multiple scattering. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light, which allows reliable detection of spectral signatures down to medicallyrelevant glucose levels.

The process of High-order harmonic generation in gases is numerically investigated in the presence of a few-cycle pulsed-Bessel-beam pump, featuring a periodic modulation in the peak intensity due to large carrier-envelope-phase mismatch. A two decade enhancement in the conversion efficiency is observed and interpreted as the consequence of a novel mechanism, namely a nonlinearly induced modulation in the phase mismatch.