A combined experimental and theoretical study of the energy loss of protons in fluorides and organic films is presented. The measurements were performed in fresh ${\mathrm{AlF}}_3$, LiF, and $N$,$N^{\prime }$-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) evaporated in situ on self-supported C or Ag foils, covering the very low energy range from $25$ keV down to $0.7$ keV. The transmission method is used in combination with time-of-flight (TOF) spectrometry. In the case of fluorides with large band gap energies (${\mathrm{AlF}}_3$ and LiF), the experimental stopping power increases almost linearly with the mean projectile velocity showing a velocity threshold at about $0.1$ a.u. These features are well reproduced by a model based on quantum scattering theory that takes into account the velocity distribution and the excitation of the active 2$p$ electrons in the $F^{-}$ anions, and the properties of the electronic bands of the insulators. In the case of the semiconductor organic film with a lower gap, the experimental stopping power increases linearly with the mean projectile velocity without presenting a clear threshold. This trend is also reproduced by the proposed model.

We used synchrotron x rays to measure the x-ray mass attenuation coefficients of gold at nine energies from $38$ to $50$ keV with accuracies of $0.1\%$. Our results are much more accurate than previous measurements in this energy range. A comparison of our measurements with calculated mass attenuation coefficients shows that our measurements fall almost exactly midway between the XCOM and FFAST calculated theoretical values, which differ from one another in this energy region by about $4\%$, even though the range includes no absorption edge. The consistency and accuracy of these measurements open the way to investigations of the x-ray attenuation in the region of the $L$ absorption edge of gold.

Time-dependent density-functional-theory (TDDFT) methods are used to calculate the orientational dependence of ionization and molecular high-order harmonic generation (MHOHG) in the CO${}_2$ molecule as a function of laser intensity $I_0⩾{10}^{14}$ W$/$cm${}^2$ for few-cycle 800  nm laser pulses. A time-series analysis is used to confirm the recollision model in MHOHG for different density potentials. It is found that at intensities $I_0>3.5\times {10}^{14}$ W$/$cm${}^2$, lower highest occupied molecular orbitals (HOMO’s) contribute significantly to ionization and to the MHOHG process. This is due to the symmetry of these orbitals. Even though such lower orbitals have higher ionization potentials (IP), ionization and MHOHG processes occur when orbital densities are maximum with laser polarization direction.

We report calculations on high-order harmonic generation in water molecules. Spectra are determined for various initial vibrational states of ${\mathrm{H}}_2\mathrm{O}$ and its isotope ${\mathrm{D}}_2\mathrm{O}$. It is demonstrated that the ratio of the spectra for ${\mathrm{D}}_2\mathrm{O}$ and ${\mathrm{H}}_2\mathrm{O}$ is close to unity when the initial state is the vibronic ground state, indicating that nuclear dynamics is of minor importance. For vibrationally excited initial states, the high-harmonic intensities show a clear dependence on both the initial-state quantum number and the isotopic species.

We present physically transparent and computationally simple method for calculating tunnel ionization rates for arbitrary bound states and arbitrary potentials in three dimensions. Here, we verify applicability of the method analytically by demonstrating that it reproduces all known analytical results for tunnel ionization from arbitrary atomic states in a single-center Coulomb potential in the presence of a constant electric field.

We propose a scheme to generate three coupled ultraslow optical solitons in a five-level tripod atomic system. We show that the detrimental distortions of the three weak probe fields due to dispersion effects under weak driving conditions can be well balanced by self- and cross-phase-modulation effects, which leads to the three coupled ultraslow temporal optical solitons with the temporal, group velocity, and amplitude values nearly matched. In contrast to other schemes, our model uses optical fibers, including multichromatic optical solitons in the stimulated Raman scattering, and produces three coupled ultraslow optical solitons in a small propagation distance of less than $1$ cm with $\frac{1}{2}$ Rabi frequency of the driving field, typically less than 100 MHz.

We present theoretical and numerical results for an all-fiber laser using self-similar parabolic pulses (“similaritons”) designed to operate using self-similar propagation regimes. The similariton laser features a frequency filter and a Sagnac loop which operate together to generate an integrated all-fiber mode-locked laser. Numerical studies show that this laser generates parabolic pulses with linear chirp in good agreement with analytical predictions. The period for propagating similariton pulses in stable regimes can vary from one to two round trips for different laser parameters. Two-round-trip-period operation in the mode-locked laser appears at bifurcation points for certain cavity parameters. The stability of the similariton regimes has been confirmed by numerical simulations for large numbers of round trips.

We report a measurement of the fine structure interval of the ${}^7\mathrm{Li}$ $10p$ atomic state with a precision significantly better than previous measurements of fine structure intervals of Rydberg ${}^7\mathrm{Li}$ $p$ states. Our result of $74.97(74)$ MHz provides an experimental value for the only $n=10$ fine structure interval which is yet to be calculated. We also report a measurement of the absolute energy of the $10p$ state and its quantum defect, which are, respectively, $42379.498(23){\mathrm{cm}}^{-1}$ and $0.04694(10)$. These results are in good agreement with recent calculations.

Quantum repeaters based on atomic ensemble quantum memories are promising candidates for achieving scalable distribution of entanglement over long distances. Recently, important experimental progress has been made toward their implementation. However, the entanglement rates and scalability of current approaches are limited by relatively low retrieval and single-photon detector efficiencies. We propose a scheme which makes use of fluorescent detection of stored excitations to significantly increase the efficiency of connection and hence the rate. Practical performance and possible experimental realizations of the new protocol are discussed.

A consistent many-body theory based on the jellium model is applied for the description of angular resolved photoelectron spectra of metal clusters anions. The results of calculations demonstrate the dominant role of the many-body effects in the formation of angular distributions of photoelectrons emitted from sodium clusters and are in a good agreement with recent experimental data. The concrete comparison of theory and experiment has been performed for the photoionization of Na${}_7$${}^{-}$ and Na${}_{19}$${}^{-}$ anions being characterized by the entirely closed shells of delocalized electrons.

We develop a general theoretical and computational framework to describe, in time domain, the exchange of momentum between light and arbitrary three-dimensional objects. Our formulation can be used to study the time evolution of optical forces on any object with linear material response, including inhomogeneous, dispersive, and absorbing dielectrics and metals. We illustrate our approach by studying the behavior of the Abraham force on an object illuminated by a sequence of electromagnetic pulses.

One-way quantum computation based on measurement and multipartite cluster entanglement offers the ability to perform a variety of unitary operations only through different choices of measurement bases. Here we present an experimental study toward demonstrating the controlled-X operation, a two-mode gate in which continuous variable (CV) four-partite cluster states of optical modes are utilized. Two quantum teleportation elements are used for achieving the gate operation of the quantum state transformation from input target and control states to output states. By means of the optical cluster state prepared off-line, the homodyne detection and electronic feeding forward, the information carried by the input control state is transformed to the output target state. The presented scheme of the controlled-X operation based on teleportation can be implemented nonlocally and deterministically. The distortion of the quantum information resulting from the imperfect cluster entanglement is estimated with the fidelity.

We show that it is possible to excite higher rotational states $J>2$ in ultracold photoassociation by two laser fields. Usually higher $J$ states are suppressed in photoassociation at ultracold temperatures in the regime of Wigner threshold laws. We propose a scheme in which one strong laser field drives photoassociation transition close to either $J=1$ or $J=2$ rotational state of a particular vibrational level of an electronically excited molecule. The other laser field is tuned near photoassociation resonance with $J>2$ rotational levels of the same vibrational state. The strong laser field induces a strong continuum-bound dipole coupling. The resulting dipole force between two colliding atoms modifies the continuum states forming continuum-bound dressed states with a significant component of higher partial waves in the continuum configuration. When the second laser is scanned near the resonance of the higher $J$ states, these states become populated due to photoassociative transitions from the modified continuum.

By considering mirror oscillation in a “tripod-scheme” laser-atom system, we advocate explorative studies of driven Dirac-like equations. Both analytical and numerical studies show that mirror oscillation can be used to drive an effective spin-orbit interaction and hence control the amplitude, the frequency, and the damping of the cold-atom Zitterbewegung oscillation. Our results demonstrate an interesting coupling between the mirror mechanical motion and a fundamental quantum coherent oscillation, opening up new means of matter-wave manipulation.

A model describing the dissipative soliton evolution in a passively mode-locked fiber laser is proposed by using the nonlinear polarization rotation technique and the spectral filtering effect. It is numerically found that the laser alternately evolves on the stable and unstable mode-locking states as a function of the pump strength. Numerical simulations show that the passively mode-locked fiber lasers with large net normal dispersion can operate on multiple pulse behavior and hysteresis phenomena. The experimental observations confirm the theoretical predictions. The theoretical and experimental results achieved are qualitatively distinct from those observed in net-anomalous-dispersion conventional-soliton fiber lasers.

We study the interaction of an atom with a quantum guided field in a weakly driven fiber-Bragg-grating (FBG) cavity. We present an effective Hamiltonian and derive the density-matrix equations for the combined atom-cavity system. We calculate the mean photon number, the second-order photon correlation function, and the atomic excited-state population. We show that due to the confinement of the guided cavity field in the fiber cross-section plane and in the space between the FBG mirrors, the presence of the atom in the FBG cavity can significantly affect the mean photon number and the photon statistics even though the cavity finesse is moderate, the cavity is long, and the probe field is weak.

We demonstrate Anderson localization of mutually incoherent counterpropagating beams in an optically induced two-dimensional photonic lattice. The effect is displayed in a system of two broad probe beams propagating head-on through a fixed disordered photonic lattice recorded in a photorefractive crystal. In addition to the steady-state localization, we also observe the dynamical localization; that is, the localization of time-changing beams. As compared to the localization of single beams, in which there exist no dynamical effects, the localization of counterpropagating beams is more pronounced and prone to instabilities.

We show how noncommuting noises could cause a Bell state ${\chi }_0$ to suffer entanglement sudden death (ESD). ESD may similarly occur when a noisy operation acts, if the corresponding Hamiltonian and Lindblad operator do not commute. We study the implications of these in special dense coding $\mathcal{S}$. When noises that cause ESD act, we show that ${\chi }_0$ may lose its capacity for $\mathcal{S}$ before ESD occurs. Similarly, ${\chi }_0$ may fail to yield information transfer better than classically possible when the encoding operations are noisy, though entanglement is not destroyed in the process.

We explore families of spatiotemporal dissipative solitons in a model of three-dimensional (3D) laser cavities including a combination of gain, saturable absorption, and transverse grating. The model is based on the complex Ginzburg-Landau equation with the cubic-quintic nonlinearity and a two-dimensional (2D) periodic potential representing the grating. Fundamental and vortical solitons are found in a numerical form as attractors in this model and their stability against strong random perturbations is tested by direct simulations. The fundamental solitons are completely stable while the vortices, built as rhombus-shaped complexes of four fundamental solitons, may be split by perturbations into their constituents separating in the temporal direction. Nevertheless, a sufficiently strong grating makes the vortices practically stable objects.