Some of the experimental measurements of the frequency shift and phase conjugation fidelity gained from previous studies of stimulated scattering (SS) of nanosecond $\left(5-10\text{ns}\right)$ near-ultraviolet (uv) $\left(\lambda =193-351\text{nm}\right)$ laser pulses in liquids (hexane, heptane, and others) are found to disagree with the theory of SS, which takes into account only linear (single-photon) light absorption. To resolve the inconsistency, SS of XeCl excimer laser radiation $\left(\lambda =308\text{nm}\right)$ with the duration of 8 ns in liquid hexane is investigated experimentally. A theoretical analysis of the results obtained revealed three nonlinear optical phenomena induced by the heating due to two-photon absorption: stimulated thermal scattering (two-photon STS-2), phase mismatch for stimulated Brillouin scattering (SBS), and phase self-modulation. The experimental SS spectrum contains two additional lines—a two-photon STS-2 line and a genuine SBS line in the near-uv region.

We elaborate on a Hilbert-Schmidt distance measure assessing the intrinsic metrological accuracy in the detection of signals imprinted on quantum probe states by signal-dependent transformations. For small signals this leads to a probe-transformation measure $\Lambda$ fully symmetric on the probe $\rho$ and the generator $G$ of the transformation $\Lambda \left(\rho ,G\right)=\Lambda \left(G,\rho \right)$. Although $\Lambda$ can be regarded as a generalization of variance, we show that no uncertainty relation holds for the product of measures corresponding to complementary generators. We show that all states with resolution larger than coherent states are nonclassical. We apply this formalism to feasible probes and transformations.

We study the physical implementation of an optimal tomographic reconstruction scheme for the case of determining the state of a multiqubit system, where trapped ions are used for defining qubits. The protocol is based on the use of mutually unbiased measurements and on the physical information described in H. Häffner et al. [Nature (London) 438, 643 (2005)]. We introduce the concept of physical complexity for different types of unbiased measurements and analyze their generation in terms of one and two qubit gates for trapped ions.

We consider a system of quantum degenerate spin-polarized fermions in a harmonic trap at zero temperature, interacting via dipole-dipole forces. We introduce a variational Wigner function to describe the deformation and compression of the Fermi gas in phase space and use it to examine the stability of the system. We emphasize the important roles played by the Fock exchange term of the dipolar interaction, which results in a nonspherical Fermi surface.

We develop a framework to calculate the density matrix of a pair of photons emitted in a decay cascade with partial “which path” ambiguity. We describe an appropriate entanglement distillation scheme which works also for certain random cascades. The qualitative features of the distilled entanglement are presented in a two dimensional “phase diagram.” The theory is applied to the quantum tomography of the decay cascade of a biexciton in a semiconductor quantum dot. Agreement with experiment is obtained.

In this paper, we study the Dzyaloshinskii-Moriya (DM) anisotropic $XX$ spin-chain model in the presence of an external homogeneous magnetic field. We found that the Berry phase of the system varies interestingly with small and large amounts of DM interaction and the magnetic field. In addition, we also considered the concurrence (i.e., the amount of entanglement) of the system, and the relationship between the concurrence and the Berry phase. Finally, we calculate the Berry phase of thermal states and verify that the results are consistent with that of the pure states.

We propose two schemes to engineer four-partite entangled Greenberger-Horne-Zeilinger (GHZ) and $W$ states in a deterministic way by using chains of (two-level) Rydberg atoms within the framework of cavity QED. These schemes are based on the resonant interaction of the atoms with a bimodal cavity that simultaneously supports, in contrast to a single-mode cavity, two independent modes of the photon field. In addition, we suggest the schemes to reveal the nonclassical correlations for the engineered GHZ and $W$ states. It is shown how these schemes can be extended in order to produce general $N$-partite entangled GHZ and $W$ states.

Analyses were conducted of various models and mechanisms of highly charged ion (HCI) and swift-heavy ion energy transfer into a solid target, such as hollow atom formation, charge screening, neutralization, shock wave generation, crater formation, and sputtering. A plasma model of space charge neutralization based on impact ionization of semiconductors at high electric fields was developed and applied to analyze HCI impacts on Si and W. Surface erosions of semiconductor and metal surfaces caused by HCI bombardments were studied by using a molecular dynamics simulation method, and the results were compared with experimental sputtering data.

We study the spectral profile of Rayleigh scattered light from molecular species trapped in optical lattices created by strong fields in the ${10}^{16}\text{W}{\text{m}}^{-2}$ range. We show that, for lattices with well depths on the order of 100 K, the motional sidebands imparted on spectra are shifted from the central Dicke-narrowed Rayleigh peak by hundreds of MHz. Our calculations for these short duration (30 ns) lattices show that these spectral features appear even in room temperature gases suggesting a new technique for measuring gas composition based on the frequency offset of the sidebands. Finally, we study the role of field-induced molecular alignment within the lattice and calculate its effect on the shape and position of the sidebands.

We investigate numerically the zero-temperature physics of the one-dimensional Bose-Hubbard model in an incommensurate cosine potential, recently realized in experiments with cold bosons in optical superlattices [L. Fallani et al., Phys. Rev. Lett. 98, 130404 (2007)]. An incommensurate cosine potential has intermediate properties between a truly periodic and a fully random potential, displaying a characteristic length scale (the quasiperiod) which is shown to set a finite lower bound to the excitation energy of the system at special incommensurate fillings. This leads to the emergence of gapped incommensurate band-insulator (IBI) phases along with gapless Bose-glass (BG) phases for strong quasiperiodic potential for both hard-core and soft-core bosons. Enriching the spatial features of the potential by the addition of a second incommensurate component appears to remove the IBI regions, stabilizing a continuous BG phase over an extended parameter range. Moreover, we discuss the validity of the local-density approximation in the presence of a parabolic trap, clarifying the notion of a local BG phase in a trapped system; we investigate the behavior of first- and second-order coherence upon increasing the strength of the quasiperiodic potential; and we discuss the ab initio derivation of the Bose-Hubbard Hamiltonian with quasiperiodic potential starting from the microscopic Hamiltonian of bosons in an incommensurate superlattice.

Light propagating through optical fiber arrays tends to localize in only a few center cores. The recent experiments in two-dimensional single-mode optical fiber arrays suggest that an interplay of deterministic and random linear and nonlinear effects might be responsible for this localization. We study this phenomenon, both analytically and numerically, in a hexagonal optical fiber array similar to that used in the experiments. Our analysis reveals that Anderson localization is evident in the linear and intermediate regimes, where a larger fraction of initial energy is returned to the center fiber due to the stochastic effects. For very high levels of input energy, the system is strongly nonlinear, with the randomness amplifying the Kerr localization.

We obtain subnatural linewidth (i.e., $<\Gamma$) for probe absorption in room-temperature Rb vapor using electromagnetically induced transparency (EIT) in a $\Lambda$ system. For stationary atoms, the EIT dip for a resonant control laser is roughly one-half as wide as the control Rabi frequency ${\Omega }_c$. But in thermal vapor, the moving atoms fill the transparency band so that the final EIT dip remains subnatural even when ${\Omega }_c⪢\Gamma$. We observe a linewidth of $\Gamma /4$ for ${\Omega }_c=8\Gamma$ in the $D_2$ line of Rb.

We investigate theoretically the main elements of manipulation of light pulses—strong nonlinear slowing down, trapping, and release on demand—in photorefractive nonlinear media. This includes a study of the slowing-down characteristics, such as delay time, amplification factor, and nonlinear broadening, for different types of photorefractive response and interaction geometries, as well as an analysis of the shape of pulses released after a long storage. The photorefractive manipulation method is shown to be applicable at ambient temperatures, low light intensities, and wide spectral ranges.

The abundance spectrum of ${\text{Na}}_{n\sim 7–140}^{-}$ anions formed by low-energy electron attachment to free nanoclusters is measured to be strongly and nontrivially restructured with respect to the neutral precursor beam. This restructuring is explained in quantitative detail by a general framework of evaporative attachment: an electron is captured by the long-range polarization potential, its energy is transferred into thermal vibrations, and dissipated by evaporative cooling. The data also affirm a formulated relation between the binding energies of cationic, neutral, and anionic clusters, and an adjustment to the prior values of dimer evaporation energies.

We introduce an exactly solvable two-channel model. As an application, we describe how it can be used for testing numerical codes.

Here we show how to generate a dark two-mode squeezed state of a trapped ion, employing a three-level ion in a V configuration with a strong decay of the excited states. The degree of squeezing can be manipulated by choosing the intensity of the driving fields. Our scheme is robust against the usual dissipation mechanism and could be implemented with present-day technology. The validity of the approximations employed in this work was tested by numerical calculations, which agreed completely with the analytical solutions.

We calculate the helicity and polarization correlation functions in the Einstein-Podolsky-Rosen-type experiments with relativistic vector bosons. Obtained results show that surprising behavior of the correlation function reported by Caban, Rembieliński, and Włodarczyk [Phys. Rev. A 77, 012103 (2008)] is an intrinsic property of relativistic quantum mechanics and not a result of the choice of the spin operator. We show that the linear polarization correlation function in the appropriately chosen state in the massless limit is the same as the correlation function in the scalar two-photon state. We show also that the polarization correlation function violates the Clauser-Horne-Shimony-Holt inequality and that the degree of this violation can increase with the particle momentum and inequality is violated maximally in the massless limit.

We consider a quantum beat laser [Scully and Zubairy, Phys. Rev. A 35 752 (1987)] as a source of entangled radiation. The system essentially consists of three-level atoms inside a doubly resonant cavity such that coherence is introduced by driving the upper two levels with a strong classical field of Rabi frequency $\Omega$. We study the dynamics of this system for different values of Rabi frequencies in the presence of cavity losses. It is shown that entanglement can be generated in this system for different initial states of the field in the two modes.

We construct a Bell inequality in terms of correlation functions for three qubits. The inequality is violated by quantum mechanics for all pure entangled states of three qubits. The strength of the violation for the GHZ state is stronger than the result given by Chen et al. [Phys. Rev. Lett. 93, 140407 (2004)], indicating that our three-qubit Bell inequality is more resistant to noise than those presented in the literature and hence is more useful in its practical applications.

Harmonic emission from cluster nanoplasmas subject to short intense infrared laser pulses is studied. In a previous publication [M. Kundu et al., Phys. Rev. A 76, 033201 (2007)] we reported particle-in-cell simulation results showing resonant enhancements of low-order harmonics when the Mie plasma frequency of the ionizing and expanding cluster resonates with the respective harmonic frequency. Simultaneously we found that high-order harmonics were barely present in the spectrum, even at high intensities. The current paper is focused on the analytical modeling of the process. We show that dynamical stochasticity owing to nonlinear resonance inhibits the emission of high-order harmonics.