A theoretical framework for studying strong-field ionization of aligned molecules is presented, and alignment-dependent ionization yields are computed for ${\text{CO}}_2$. Our calculations are in unprecedented agreement with recent experiments. We find that the ionization process is affected by intermediate resonance states, and the alignment-dependent ionization yields do not follow the electron density of the initial states. The theory explains the breakdown of semianalytical theories, such as the molecular tunneling theory and strong-field approximation, where excited electronic structure is neglected.

We investigate how quantitatively reliable is the classical trajectory Monte Carlo description of ionization dynamics, and related processes, in one-electron atoms submitted to strong and short laser pulses. The classical results for ionization probability and densities, ejected electron, and harmonic radiation spectra are compared to quantum-mechanical references obtained by solving the time-dependent Schrödinger equation. Illustrations are given for model one-dimensional H system in linearly polarized pulses.

The spontaneous decay of a multilevel atom interacting with the electromagnetic field in free space is investigated with a unitary transformation method, which is introduced in order to include all rotating and counter-rotating terms in the Hamiltonian. By using the ground state of the total Hamiltonian, the evolution of the effective decay rate and the energy shift are calculated. When the atomic transition frequency is smaller than the central frequency of the spectrum, the Zeno effect dominates, and if the atomic transition frequency is larger than the central frequency, the anti-Zeno effect will dominate. The time evolution of the energy shift is obtained. The counter-rotating terms lead to a shift toward the low frequency region for the frequency distribution of the emitted photon.

We demonstrate a phenomenon very similar to electromagnetically induced transparency using a shaped ultrafast laser pulse. Pulse shaping allows us to produce probe and coupling pulses with arbitrary intensities and time delays. The coupling Rabi frequency and probe bandwidth are both on the order of 1 THz, which is much larger than the natural or Doppler broadened linewidth of the probe transition. Important dynamics associated with a time-dependent coupling field are discussed.

We propose a scheme to split a cloud of cold noninteracting neutral atoms based on their dipole interaction with a single structured light beam which exhibits parabolic cylindrical symmetry. Using semiclassical numerical simulations, we establish a direct relationship between the general properties of the light beam and the relevant geometric and kinematic properties acquired by the atomic cloud as it passes through the beam.

We analyze the non-Markovian dynamics of a quantum system subject to spontaneous collapse in space. After having proved, under suitable conditions, the separation of the center-of-mass and relative motions, we focus our analysis on the time evolution of the center of mass of an isolated system (free-particle case). We compute the explicit expression of the Green’s function, for a generic Gaussian noise, and analyze in detail the case of an exponential correlation function. We study the time evolution of average quantities, such as the mean position, momentum, and energy. We eventually specialize to the case of Gaussian wave functions and prove that all basic facts about collapse models, which are known to be true in the white-noise case, hold also in the more general case of non-Markovian dynamics.

We introduce the concept of distillability sudden death, i.e., free entangled states can evolve into nondistillable (bound entangled or separable) states in finite time under local noise. We describe the phenomenon through a specific model of local dephasing noise and compare the behavior of states in terms of the Bures fidelity. Then we propose a few methods to avoid distillability sudden death of states under (general) local dephasing noise so that free entangled states can be robust against decoherence. Moreover, we find that bound entangled states are unstable in the limit of infinite time.

We show how to perfectly transfer, without state initialization and remote collaboration, arbitrary functions in interacting boson lattices. We describe a possible implementation of state transfer through bosonic atoms trapped in optical lattices or polaritons in on-chip coupled cavities. Significantly, a family of Hamiltonians, both linear and nonlinear, is found which are related to the Bose-Hubbard model and that enable the perfect transfer of arbitrary functions. It is shown that the state transfer between two sites in two-dimensional lattices can result in quantum interference due to the different numbers of intermediate sites in different paths. The signature factor in nuclear physics can be useful to characterize this quantum interference.

The general theory of electromagnetic-fluctuation-induced interactions in dielectric bodies as formulated by Dzyaloshinskii, Lifshitz, and Pitaevskii is rewritten as a perturbation theory in terms of the spatial contrast in (imaginary) frequency dependent dielectric function. The formulation can be used to calculate the Casimir-Lifshitz forces for dielectric objects of arbitrary geometry, as a perturbative expansion in the dielectric contrast, and could thus complement the existing theories that use perturbation in geometrical features. We find that expansion in dielectric contrast recasts the resulting Lifshitz energy into a sum of the different many-body contributions. The limit of validity and convergence properties of the perturbation theory is discussed using the example of parallel semi-infinite objects for which the exact result is known.

Experimental measurements of the kinetic energy distribution spectra of ${\text{H}}^{+}$ fragment ions released during radiolysis of water molecules in collision with 20, 50, and 100 keV proton projectiles and 35, 200, 400, and 1000 eV electron projectiles are reported using a pulsed beam and drift tube time-of-flight based velocity measuring technique. The spectra show that ${\text{H}}^{+}$ fragments carrying a substantial amount of energy are released, some having energies well in excess of 20 eV. The majority of the ions lie within the 0–5 eV energy range with the proton spectra showing an almost constant profile between 1.5 and 5 eV and, below this, increasing gradually with decreasing ejection energy up to the near zero energy value while the electron spectra, in contrast, show a broad maximum between 1 and 3 eV and a pronounced dip around 0.25 eV. Beyond 5 eV, both projectile spectra show a decreasing profile with the electron spectra decreasing far more rapidly than the proton spectra. Our measured spectra thus indicate that major differences are present in the collision dynamics between the proton and the electron projectiles interacting with gas phase water molecules.

We investigate high-order above-threshold ionization (HATI) of diatomic molecules having different symmetries by an elliptically polarized laser field using the modified molecular strong-field approximation. The yields of high-energy electrons contributing to the plateau region of the photoelectron spectra strongly depend on the employed ellipticity. This is more pronounced if the major axis of the polarization ellipse is parallel or perpendicular to the molecular axis and at the end of the high-energy plateau. For the ${\text{O}}_2$ molecule (characterized by ${\pi }_{\text{g}}$ symmetry) the maximum yield is observed for some value of the ellipticity $\epsilon$ different from zero. On the other hand, in the same circumstances, the ${\text{N}}_2$ molecule $\left({\sigma }_{\text{g}}\right)$ behaves as an atom, i.e., the yield is maximum for $\epsilon =0$. These characteristics of the photoelectron spectra remain valid in a wide region of the molecular orientations and laser peak intensities. The symmetry properties of the molecular HATI spectra are considered in detail: by changing the molecular orientation one or other type of the symmetry emerges or disappears. Presenting differential ionization spectra in the ionized electron energy-emission angle plane we have observed similar interference effects as in the HATI spectra governed by a linearly polarized field.

We study pairing of an interacting three-component Fermi gas in two dimensions. By using a mean-field theory to decouple the interactions between different pairs of Fermi components, we study the free energy landscapes as a function of various system parameters including chemical potentials, binding energies, and temperature. We find that the $s$-wave pairing channel is determined by both chemical potentials and the interaction strengths between the three available channels. We find a second-order thermal phase transition and a series of first-order quantum phase transitions for a homogenous system as we change the parameters. In particular, for symmetric parameters, we find the simultaneous existence of three superfluid orders as well as re-entrant quantum phase transitions as we tune the parameters.

We derive nonlocal coupled-mode equations for a Bragg grating embedded in a medium with nonlocal nonlinearity. Using these equations, we study the oscillatory instability of nonlocal Bragg solitary waves and demonstrate that collisions between them result in fusion into a standing pulse (or breather), possibly with generation of additional jets, in a broad range of parameters. The results are explained by considering the effect of spatial dispersion induced by the nonlocal nonlinear response.

Asymmetric profiles have been observed in the recombination cross section of Be-like Bi obtained by measuring the electron energy dependence of the ion abundance ratio in an electron-beam ion trap. In contrast to the previous x-ray measurements, the present measurement gives the integrated recombination cross section with higher statistical quality, which provides a benchmark to test the relativistic theory involving the interference between the resonant and continuum states. The comparison with our theoretical study shows that the Breit interaction plays an important role in this case.

We study bound states of two fermions with opposite spins in an extended Hubbard chain. The particles interact when located both on a site or on adjacent sites. We find three different types of bound states. Type $U$ is predominantly formed of basis states with both fermions on the same site, while two states of type $V$ originate from both fermions occupying neighboring sites. Type $U$ and one of the states from type $V$ are symmetric with respect to spin flips. The remaining one from type $V$ is antisymmetric. $V$ states disappear by merging with the two-particle continuum below some critical wave number. All bound states become compact for wave numbers at the edge of the Brillouin zone.

We consider the hyperfine transitions in ultracold collisions of hydrogen (H) and antihydrogen $\left(\overline{\text{H}}\right)$ atoms. The cross sections for transitions between various spin states are calculated. We show that hyperfine transitions in $\overline{\text{H}}-\text{H}$ collisions are basically driven by the strong force between proton and antiproton.

In the photoionization of an atom endohedrally confined in a fullerene the electrons directly ionized from the atom partially reflect from the cage. However, the valence atomic electrons can also eject from the cage collaterally with their direct emission. The reflective and the collateral amplitudes oscillate in the electron’s momentum space with frequencies determined by their path differences from the direct amplitude. Resulting cross sections reveal the confining geometry in the Fourier conjugate domain. The frequency pattern distinguishes the atomic emission from the fullerene emission.

In this Rapid Communication we report an experimental observation of temporal delay control of large-spectral-bandwidth multimode laser pulses by means of electromagnetically induced transparency. We achieved optically controllable retardation of laser pulses with an input spectral bandwidth of 3.3 GHz with limited temporal distortion and excellent values of the delay-bandwidth product. The experimental results compare favorably with a theoretical analysis.

Motivated by the growing importance of the fidelity and fidelity susceptibility (FS) in quantum critical phenomena, we use these concepts to describe the pulse propagation inside the dispersive media. It is found that there is a dramatic change in the fidelity and the FS of the pulse at a critical propagation distance inside a dispersive medium, and whether such a dramatic change for a light pulse occurs or not strongly depends on both the dispersive strength of the media and the pulse property. We study in detail about the changes in the fidelity and the FS for both a smooth and a truncated Gaussian pulse through the abnormal and normal dispersive media, where the group velocities are well defined. Our results show that both the fidelity and the FS could be very useful to determine whether the pulse is completely distorted or not at the critical distance; therefore it would be very helpful to find the maximal effective propagation region of the pulse’s group velocity, in terms of the changes in the pulse’s fidelity and FS.

Spatial displacements of the probe and generated four-wave mixing beams are observed in a three-level V-type, as well as a two-level atomic system near resonance. The observed spatial shift curves reflect the typical enhanced cross-Kerr nonlinear dispersion properties in the electromagnetically induced transparency (EIT) systems. The spatial beam displacements are controlled by the strong control laser beam and the atomic density. Studying such controlled spatial beam shifts can be important in image storage and in generating spatially correlated (entangled) laser beams in multilevel EIT systems.