Site-specific fragmentation caused by $\mathrm{Si}:2p$ core-level photoionization of ${\mathrm{F}}_3{\mathrm{SiCH}}_2{\mathrm{CH}}_2\mathrm{Si}({\mathrm{CH}}_3{)}_3$ vapor was studied by means of high-resolution energy-selected-electron photoion-photoion triple-coincidence spectroscopy. The ab initio molecular orbital method was used for the theoretical description. ${{\mathrm{F}}_3{\mathrm{SiCH}}_2{\mathrm{CH}}_2}^{+}\text{−}{\mathrm{Si}({\mathrm{CH}}_3{)}_3}^{+}$ ion pairs were produced by the $2p$ photoionization of the Si atoms bonded to the three methyl groups, and ${\mathrm{SiF}}^{+}$-containing ion pairs were produced by the $2p$ photoionization of the $\mathrm{Si}$ atoms bonded to the three F atoms.

We predict the resonance-enhanced magnetic field dependence of atom-dimer relaxation and three-body recombination rates in a ${}^{87}\mathrm{Rb}$ Bose-Einstein condensate close to $1007\mathrm{G}$. Our exact treatments of three-particle scattering explicitly include the dependence of the interactions on the atomic Zeeman levels. The Feshbach resonance distorts the entire diatomic energy spectrum, causing interferences in both loss phenomena. Our two independent experiments confirm the predicted recombination loss over a range of rate constants that spans four orders of magnitude.

We experimentally demonstrate a proof-of-principle of a previously proposed “channelization” architecture for wideband slow-light propagation in atomic vapors using electromagnetically induced transparency (EIT). We use two optical frequencies to generate a sine wave signal which is delayed in rubidium vapor. The optical frequencies were tuned near the EIT resonances of two Zeeman sublevels, which are shifted from each other well beyond the EIT linewidth by a uniform magnetic field. We varied the Zeeman shift between these two levels (relative to the optical frequency splitting) and measured the delay versus Zeeman shift. Significant delays were observed and were in agreement with a theoretical model treating each Zeeman sublevel as part of an independent three-level system. We achieved delay of a signal with a bandwidth 16 times the EIT linewidth and confirmed our earlier theoretical models that delay occurs only when the optical spectral separation slightly exceeds the Zeeman splitting.

We have proposed a way to obtain large optically controlled delay for subnanosecond pulses and simultaneously avoid the pulse distortions via stimulated Brillouin scattering (SBS) in optical fibers at cw pumping by the use of longitudinally nonuniform fibers with the Brillouin frequency linearly varying with distance. If the range of Brillouin frequency variation along the fiber covers the whole pulse spectrum, the delay of subnanosecond pulses is linearly proportional to the gain, could be larger than the pulse duration, and the pulse broadening is minimum. We have shown this by solving three-wave SBS equations for realistic fiber lengths, both single subnanosecond pulses and sequences of subnanosecond pulses.

The Fourier-transform ghost imaging of both amplitude-only and pure-phase objects was experimentally observed with classical incoherent light at Fresnel distance by a lensless scheme. The experimental results are in good agreement with the standard Fourier transform of the corresponding objects. This scheme provides a route toward aberration-free diffraction-limited three-dimensional images with classically incoherent thermal light (or neutrons), which have no resolution and depth-of-field limitations of lens-based tomographic systems.

We consider a model dissipative quantum-mechanical system realized by coupling a quantum oscillator to a semi-infinite classical string which serves as a means of energy transfer from the oscillator to the infinity and thus plays the role of a dissipative element. The coupling between the two—quantum and classical—parts of the compound system is treated in the spirit of the mean-field approximation and justification of the validity of such an approach is given. The equations of motion of the classical subsystem are solved explicitly and an effective dissipative Schrödinger equation for the quantum subsystem is obtained. The proposed formalism is illustrated by its application to two basic problems: the decay of the quasistationary state and the calculation of the nonlinear resonance line shape.

Multistate generalizations of Landau-Zener model are studied by summing entire series of perturbation theory. A technique for analysis of the series is developed. Analytical expressions for probabilities of survival at the diabatic potential curves with extreme slope are proved. Degenerate situations are considered when there are several potential curves with extreme slope. Expressions for some state-to-state transition probabilities are derived in degenerate cases.

We propose a modified protocol of atomic state teleportation for the scheme proposed by Bose et al. [Phys. Rev. Lett. 83, 5158 (1999)]. The modified protocol involves an additional stage in which quantum information distorted during the first stage is fully recovered by a compensation of the damping factor. The modification makes it possible to obtain a high fidelity of teleported state for cavities that are much worse than that required in the original protocol, i.e., their decay rates can be over $25$ times larger. The improvement in the fidelity is possible at the expense of lowering the probability of success. We show that the modified protocol is robust against dark counts.

We report a precise determination of the static polarizability of the $8s{}^{2}S_{1∕2}$ state of atomic cesium, carried out jointly through experimental measurements of the dc Stark shift of the $6s{}^{2}S_{1∕2}\to 8s{}^{2}S_{1∕2}$ transition using Doppler-free two-photon absorption and theoretical computations based on a relativistic all-order method. We enhance the precision of the measurement by imposing phase-modulation sidebands on the laser beam and by using a pair of vapor cells, one of which serves as a reference, and measuring the absorption spectrum in each cell with a single scan of the laser frequency. The measured value for the polarizability of the $8s$ state is $\mathrm{38,060}\pm 250a_0^3$, in very good agreement with our theoretical value of $\mathrm{38,260}\pm 290a_0^3$. In addition, the small difference in the Stark shift measurement for the two hyperfine states that we examine yields a variation in the polarizability due to the magnetic dipole contact interaction of $290\pm 30a_0^3$.

We report experimental evidence of the sympathetic cooling of ${}^{39}\mathrm{K}$ with ${}^{87}\mathrm{Rb}$ down to $1\mathrm{\mu }\mathrm{K}$, obtained in a tight-confining magnetic trap. This allowed us to perform a direct measurement of the elastic cross section of ${}^{39}\mathrm{K}$ below $50\mathrm{\mu }\mathrm{K}$. The result obtained for the triplet scattering length, $a_T=-51\left(7\right)$ Bohr radii, agrees with previous results derived from photoassociation spectra and from Feshbach spectroscopy of ${}^{40}\mathrm{K}$.

A method is introduced to renormalize the zero-range interaction for use in mean-field and many-body theory, starting from two-body calculations. The density-renormalized $\delta$-function interaction is then applied using mean-field theory to a two-component fermion gas and compared with diffusion Monte Carlo simulations and conventional mean-field calculations. In the unitarity limit, the equation of state exhibits the expected behavior $\mu \propto {\rho }^{2∕3}$, with a parameter $\beta =-0.492$, which is consistent with recent experiments.

We present theoretical calculations of the energy-loss straggling of C, Al, Si, and Cu targets for H, He, and Li ions in the range of intermediate to high energies $(0.01–10\mathrm{MeV}∕\mathrm{u})$. These calculations have been done by employing the dielectric formalism and by considering the different equilibrium charge states of the swift ion inside the solid as a function of its energy. Two different models are used: the Mermin energy-loss functions combined with generalized oscillator strengths (MELF-GOS) and the shellwise application of the local plasma approximation (SLPA). The MELF-GOS describes the target outer-electron excitations through a fitting to experimental data in the optical limit, employing a linear combination of Mermin-type energy-loss functions; the excitations of the inner-shell electrons are taken into account by means of generalized oscillator strengths. The SLPA employs a free-electron-gas model for the target valence electrons and the local density approximation for each shell of target electrons separately by using Hartree-Fock atomic wave functions. The results of the energy-loss straggling obtained by the two independent models show good agreement with the available experimental data. The calculated energy-loss straggling tends at high energies to the Bohr value and takes values below it at intermediate energies. The Bethe-Livingston shoulder (or overshooting) at intermediate energies does not appear in the present calculations. We find that the energy-loss straggling normalized to $Z_{\mathrm{P}}^2$ is almost independent of the ion atomic number $Z_{\mathrm{P}}$; therefore, the results for H, He, and Li projectiles in each target can be approximated by a universal curve at high energies.

We present the detection of a two-photon transition based on stimulated emission. This measurement was performed in rubidium for the $5S\text{−}5D_{5∕2}\text{−}5P_{3∕2}$ transition, using two low-cost diode lasers. Several detection schemes were tested. We reached the best results by probing the circular birefringence of the excited vapor, with the polarization analysis of the amplified laser beam.

We have realized adjustable multiple sub-Doppler traps (SDT’s) in a six-beam magneto-optical trap (MOT) under asymmetric trap conditions. In the simplest case, one obtains an array of three SDT’s, one usual trap at the origin and two additional traps symmetrically but oppositely located at equal and controllable distances from the origin, in good agreement with theoretical calculations. The easily adjustable array of SDT’s readily available in the asymmetric MOT may open the possibility of novel atom optics or quantum optics experiments such as atom interferometer or quantum information.

Atomtronics focuses on atom analogs of electronic materials, devices, and circuits. A strongly interacting ultracold Bose gas in a lattice potential is analogous to electrons in solid-state crystalline media. As a consequence of the gapped many-body energy spectrum, cold atoms in a lattice exhibit insulatorlike or conductorlike properties. $P$-type and $N$-type material analogs are created by introducing impurity sites into the lattice. Current through an atomtronic wire is generated by connecting the wire to an atomtronic battery which maintains the two contacts at different chemical potentials. The design of an atomtronic diode with a strongly asymmetric current-voltage curve exploits the existence of superfluid and insulating regimes in the phase diagram. The atom analog of a bipolar junction transistor exhibits large negative gain. Our results provide the building blocks for more advanced atomtronic devices and circuits such as amplifiers, oscillators, and fundamental logic gates.

We investigate a dilute mixture of bosons and spin-polarized fermions in one dimension. With an attractive Bose-Fermi scattering length the ground state is a self-bound droplet, i.e., a Bose-Fermi bright soliton where the Bose and Fermi clouds are superimposed. We find that the quantum fluctuations stabilize the Bose-Fermi soliton such that the one-dimensional bright soliton exists for any finite attractive Bose-Fermi scattering length. We study density profile and collective excitations of the atomic bright soliton showing that they depend on the bosonic regime involved: mean-field or Tonks-Girardeau.

We study the reflection of two counterpropagating modes of the light field in a ring resonator by ultracold atoms either in the Mott insulator state or in the superfluid state of an optical lattice. We obtain exact numerical results for a simple two-well model and carry out statistical calculations appropriate for the full lattice case. We find that the dynamics of the reflected light strongly depends on both the lattice spacing and the state of the matter-wave field. Depending on the lattice spacing, the light field is sensitive to various density-density correlation functions of the atoms. The light field and the atoms become strongly entangled if the latter are in a superfluid state, in which case the photon statistics typically exhibits complicated multimodal structures.

Pure states are fundamental for the implementation of quantum technologies, and several methods for the purification of the state of a quantum system $S$ have been developed in the past years. In this work we describe a mechanism leading to purification of mixed states, based on the interaction of $S$ with an auxiliary system $P$. Considering two-level systems and assuming a particular interaction between them, we study how the dynamical parameters of the system $P$ affect the purification of $S$. By using analytical and numerical tools, we show that the purification process exhibits a resonant behavior in both the cases of system isolated from the external environment or not.

We have previously calculated the cross section for radiative formation of the interesting bound state consisting of a positron bound to helium, where the atomic electrons are in the triplet spin state. That process uses the metastable triplet helium system as target, and, as expected, it has a very small cross section. In this paper we examine a more probable process in which the state of interest is produced in an exchange rearrangement collision between a positronium atom and the singlet helium ground state: $\mathrm{Ps}+\mathrm{He}\left({}^{1}S^{\mathrm{e}}\right)\to \mathrm{Ps}{\mathrm{He}}^{+}\left({}^{3}S^{\mathrm{e}}\right)+e^{-}$. The present calculation is done in the plane-wave Born approximation, using simple initial and final wave functions and compares post and prior forms.

Electron transfer in the presence of a laser field is considered for the $p\text{−}\mathrm{Ne}$ and $p\text{−}\mathrm{Ar}$ collision systems. The calculations are based on a time-dependent density functional theory framework and the basis generator method for orbital propagation. Significant enhancements of electron transfer at low collision energy are found and interpreted with the help of molecular potential curves. For the $p\text{−}\mathrm{Ar}$ system a moderately intense field at 800 or $1064\mathrm{nm}$ wavelength is sufficient to increase the total cross section by more than a factor of 2. Contrary to previously studied cases this scenario can be realized and tested in the laboratory.