High-resolution $\left(\text{K}3p\sigma \text{and}\pi \right)\to \sigma$ absorption spectrum of KF in the photon energy range of 18.2–19.4 eV was measured at the new FINEST beamline branch on the I3 beamline on MAX III. The experimental spectrum is presented and interpreted using nonrelativistic ab initio molecular calculations corrected with perturbation theory treatment to account for spin-orbit interaction. Resonant Auger decay recorded at the strongest resonances is also presented and reproduced by theoretical calculations. Also a brief introduction to the FINEST beamline branch is presented.

We study a trapped system of fermions with a zero-range two-body interaction using the shell-model Monte Carlo method, providing ab initio results for the low particle number limit where mean-field theory is not applicable. We present results for the $N$-body energies as function of interaction strength, particle number, and temperature. The subtle question of renormalization in a finite model space is addressed and the convergence of our method and its applicability across the BCS-BEC crossover is discussed. Our findings indicate that very good quantitative results can be obtained on the BCS side, whereas at unitarity and in the BEC regime the convergence is less clear. Comparison to $N=2$ analytics at zero and finite temperature, and to other calculations in the literature for $N>2$ show very good agreement.

We propose a technique capable of imaging a distinct physical object with sub-Rayleigh resolution in an ordinary far-field imaging setup using single-photon sources and linear optical tools only. We exemplify our method for the case of a rectangular aperture and two or four single-photon emitters obtaining a resolution enhanced by a factor of 2 or 4, respectively.

We investigate light propagation in the materials with periodically modulated gain-loss profile in both transverse and longitudinal directions with respect to the direction of light propagation. We predict the effects of self-collimation (diffraction-free propagation) of the beams, as well as the superdiffusion (spatial frequency filtering) of the beams depending on the geometry of the gain-loss lattice, and justify the predictions by numerical simulations of the paraxial wave propagation equations.

Ideally, strong nonlinearities could be used to implement quantum gates for photonic qubits by well-controlled two-photon interactions. However, the dependence of the nonlinear interaction on frequency and time makes it difficult to preserve a coherent pulse shape that could justify a single-mode model for the time-frequency degree of freedom of the photons. In this paper, we analyze the problem of temporal multimode effects by considering the pulse shape of the average output field obtained from a coherent input pulse. It is shown that a significant part of the two-photon state transformation can be derived from this semiclassical description of the optical nonlinearity. The effect of a nonlinear system on a two-photon state can then be determined from the density-matrix dynamics of the coherently driven system using input-output theory. As an example, the resonant nonlinearity of a single two-level atom is characterized. The results indicate that the most efficient nonlinear effect may not be the widely studied single-mode phase shift, but the transfer of one of the photons to an orthogonal mode distinguished by its temporal and spectral properties.

We investigate the directional mode-hopping in semiconductor ring lasers in the limit of small noise intensity. We show how only long time scales are involved in the hopping process. In such limit, the initial stochastic rate equations can be reduced to an auxiliary Hamiltonian system, and the dependence of the hopping on the laser parameters can be investigated. The predictions made from the reduced model agree well with the results obtained by simulating the full rate-equation system.

Photoelectron angular distributions from fixed-in-space ${\text{H}}_2$ molecules exposed to ultrashort xuv laser pulses have been evaluated. The theoretical method is based on the solution of the time-dependent Schrödinger equation in a basis of stationary states that include all electronic and vibrational degrees of freedom. Asymmetric angular distributions are observed as a consequence of the delayed ionization from the ${\text{H}}_2$ doubly excited states, which induces interferences between gerade and ungerade ionization channels. The analysis of this asymmetry as a function of pulse duration can provide an estimate of the corresponding autoionization widths.

We theoretically study the scaling with the driving wavelength $\lambda$ of the high-order harmonic generation (HHG) under the simultaneous irradiation of an extreme ultraviolet (xuv) pulse. Surprisingly, when the cut-off energy and ionization yield are fixed, the harmonic yield is nearly independent of $\lambda$. We identify its origin as the combination of the initial spatial width of the states excited by the xuv pulse, making the wave packet spreading less prominent and the shallowing of the ionization potential, which suggests complex nature of the wavelength dependence of HHG.

The mechanical behavior of a transformation based spherical cloak under wave illumination is derived. We show that the equatorial region of the cloak is subject to much higher stress than the polar regions, where the polar axis is defined along the wave propagation direction. These forces do not exist before transformation but stem from the squeezed electromagnetic space. The trajectory of the ray can be interpreted as a result of the recoil force that the cloak exerts upon the ray. The total radiation pressure on an ideal cloak is shown to be exactly zero, effecting a stationary cloak.

We obtain an exact solution of the Dirac equation in $\left(2+1\right)$ dimensions in the presence of a constant magnetic field normal to the plane together with a two-dimensional Dirac-oscillator potential coupling. The solution space consists of positive- and negative-energy solutions, each of which splits into two disconnected subspaces depending on the sign of an azimuthal quantum number $k=0,\pm 1,\pm 2,\dots$ and whether the cyclotron frequency is larger or smaller than the oscillator frequency. The spinor wave function is written in terms of the associated Laguerre polynomials. For negative $k$, the relativistic energy spectrum is infinitely degenerate due to the fact that it is independent of $k$. We compare our results with already published work and point out the relevance of these findings to a systematic formulation of the relativistic quantum Hall effect in a confining potential.

A quantum channel models the interaction between the system we are interested in and its environment. Such a model can capture the main features of the interaction, but, because of the complexity of the environment, we cannot assume that it is fully accurate. We study the robustness of quantum error correction operations against completely unexpected and subsequently undetermined type of channel uncertainties. We find that a channel-adapted optimal error correction operation does not only give the best possible channel fidelity but it is more robust against channel alterations than any other error correction operation. Our results are valid for Pauli channels and stabilizer codes, but based on some numerical results, we believe that very similar conclusions can be drawn also in the general case.

This paper presents a quantum-mechanical analysis of the interaction of one electron with a physical dipole (two physically separated charges). Aspects of threshold laws in the continuous spectrum are treated. In addition there are determinations of energies of some dipole bound states. The bound-state calculations are used as a model for certain high dipole moment molecules, where, together with empirical data, an equivalent dipole length may be determined. These model calculations predict that the bound dipole orbital in high dipole molecule ions should have a node between its valence part and the more remote part where the majority of the charge resides. Some results from the two parts of the treatment are brought together to calculate the asymmetry factor of the photoelectron signal for uracil, measured by Schiedt et al.

We report on the experimental determination of the palladium $L$-subshell Coster-Kronig (CK) transition yields via high-resolution measurements of the $L{\alpha }_{1,2}$ $\left(L_3-M_{4,5}\right)$ and $L{\beta }_1$ $\left(L_2-M_4\right)$ x-ray emission lines. The $L$ x-ray spectra were recorded by means of curved crystal spectrometers employing energy-tunable synchrotron radiation for fluorescence production. The CK yields were derived from the relative $L$ x-ray intensity jumps at the $L$ edges by fitting the fluorescence intensities as a function of the photon energy to the photoionization cross sections. The $L$ x-ray intensities were corrected for solid-state effects which were estimated from the comparison of the measured and theoretical Pd $L$-edge x-ray-absorption spectra. Thanks to high resolution, the partial CK yield $f_{13}^{L_1{L}_{3}M}$ could be extracted from the intensities of the resolved $L\alpha M$ satellite transitions. For $f_{23}$, $f_{12}$, and $f_{13}$ CK rates, values of $0.164\pm 0.033$, $0.047\pm 0.001$, and $0.730\pm 0.039$ were found, respectively. For the partial CK yields $f_{13}^{L_1{L}_{3}M}$ and $f_{13}^{L_1{L}_{3}N}$, results of $0.406\pm 0.023$ and $0.324\pm 0.032$, respectively, were obtained.

Quantum calculations for the excitation of the asymmetric modes of the ${\text{CF}}_4$ target gas, ${\nu }_3$ and ${\nu }_4$, by impact of low-energy electrons and positrons are carried out in the energy range around 1 eV and are compared with recent experimental findings. The similarities and differences between the two types of projectiles, and the two different modes, are analyzed and discussed vis à vis the present accord with the experimental results.

We study the variation in the positions of two magnetically tuned zero energy Feshbach resonances when a parallel superimposed electric field is applied. We show that their variation as a function of the electric field follows a simple analytical law and is then predictable. We find that depending on the initial state of the diatomic molecule the resonance is either shifted to higher or to lower values of the magnetic field when the electric field is applied. We calculate the close-coupling lifetimes of these resonances and show that they also follow a simple law as a function of both the magnetic and the electric field. We demonstrate using this expression that the lifetime of the resonances can be maximized by choosing an appropriate value of the applied electric field and found a good agreement with the results of our close-coupling calculations. These results could be checked in future experiments dedicated to the ${}^3\text{He}+\text{NH}\left({}^3\Sigma \right)$ collisions

We study the properties of two-color nonlinear localized modes which may exist at the interfaces separating two different periodic photonic lattices in quadratic media, focusing on the impact of phase mismatch of the photonic lattices on the properties, stability, and threshold power requirements for the generation of interface localized modes. We employ both an effective discrete model and continuum model with periodic potential and find good qualitative agreement between both models. Dynamic excitation of interface modes shows that a two-color interface twisted mode splits into two beams with different escaping angles and carrying different energies when entering a uniform medium from the quadratic photonic lattice. The output position and energy contents of each two-color interface solitons can be controlled by judicious tuning of the lattice parameters.

We discuss stationary light created by a pair of counterpropagating control fields in $\Lambda$-type atomic gases with electromagnetically induced transparency for the case of negligible Doppler broadening. In this case, the secular approximation used in the discussion of stationary light in hot vapors is no longer valid. We discuss the quality of the effective light-trapping system and show that in contrast to previous claims it is finite even for vanishing ground-state dephasing. The dynamics of the photon loss is in general nonexponential and can be faster or slower than in hot gases.

In a macroscopic realm, in which photons are too many to be counted by any photon-counting detector, photon statistics can be measured by using detectors simply endowed with linear response. We insert one of such detectors in a conventional photon-counting apparatus, which returns a voltage every time the detector responds to light by generating a number of elementary charges via its primary photodetection process. We only assume that, when a single charge is photogenerated, the probability density of the voltages is a distribution that is narrow with respect to its mean value. Under this hypothesis the output voltages can be suitably binned so that their probability distribution is the same as that of the photogenerated charges, that is, of the detected photons.

We propose a continuous time quantum search algorithm using a generalization of the Jaynes-Cummings model. In this model the states of the atom are the elements among which the algorithm realizes the search, exciting resonances between the initial and the searched states. This algorithm behaves like Grover’s algorithm; the optimal search time is proportional to the square root of the size of the search set and the probability to find the searched state oscillates periodically in time. In this frame, it is possible to reinterpret the usual Jaynes-Cummings model as a trivial case of the quantum search algorithm.