A promising technique of atom slowing is proposed. It is based upon the dispersive interaction of atoms with optical potential pulses generated by a far-off-resonance standing wave modulated in time. Each pulse reduces the velocity by a small amount. By repeating the process thousands of times, the velocity can be lowered from several hundreds of meters per second down to almost zero, over a path as short as $20\mathrm{c}\mathrm{m}$. In the absence of any random recoil process, the initial characteristics of the beam are preserved.

We study the effects of nonzero photon momentum on the triply differential cross section (TDCS) for ($\gamma ,2e$) processes. Due to the low value of the photon momentum, these effects are weak and manifest only in special kinematical conditions such as the back-to-back emission of the electrons with equal energy sharing. Helium and a few light heliumlike ions are treated in detail. Quite unexpectedly, the magnitude of these effects is maximal for relatively small photon energies. However, although this effect on the TDCS remains rather small, of the order of a few mb eV${}^{-1}$ sr${}^{-2}$, it is sufficient to be observed experimentally.

The dissociation of D${}_3$${}^{+}$ in intense ultrashort laser pulses is investigated using an improved coincidence three-dimensional momentum imaging method that allows clear separation of all fragmentation channels and the determination of the kinetic energy release down to zero. Our results, using 10-fs, 790-nm pulses, suggest that a large peak at low kinetic energy release is associated with the D${}^{+}$ + D${}_2$ dissociation channel of D${}_3$${}^{+}$. The most likely dissociation pathways leading to two-body breakup of D${}_3$${}^{+}$ are identified with additional measurements using 25-fs, 790-nm and 40-fs, 395-nm pulses. We also show that the slow D${}^{+}$ + D${}_2$ dissociation dynamics can be manipulated by the pulse duration.

The scattering dynamics of a particle incident on a model system with three bound states in the presence of a localized radiation field is studied using Floquet scattering theory. An analytic expression for the Floquet S matrix is derived for the case of a radiation field containing two frequency components. The radiation field destabilizes and can entangle the bound states forming quasibound states that fundamentally alter the scattering dynamics of an incident particle.

We study interacting one-dimensional two-component mixtures of cold atoms in a random potential, and extend the results reported earlier [Phys. Rev. Lett. 105, 115301 (2010)]. We construct the phase diagram of a disordered Bose-Fermi mixture as a function of the strength of the Bose-Bose and Bose-Fermi interactions, and the ratio of the bosonic sound velocity and the Fermi velocity. Performing renormalization group and variational calculations, three phases are identified: (i) a fully delocalized two-component Luttinger liquid with superfluid bosons and fermions, (ii) a fully localized phase with both components pinned by disorder, and (iii) an intermediate phase where fermions are localized but bosons are superfluid. Within the variational approach, each phase corresponds to a different level of replica symmetry breaking. In the fully localized phase we find that the bosonic and fermionic localization lengths can largely differ. We also compute the long-wavelength asymptotic behavior of the momentum distribution as well as that of the structure factor of the atoms (both experimentally accessible), and discuss how the three phases can be experimentally distinguished.

We study interacting Rashba-Dresselhaus fermions in two spatial dimensions. First, we present an exact solution to the two-particle bound-state problem of spin-orbit (SO)-coupled fermions for arbitrary Rashba and Dresselhaus SO interactions. An exact molecular-wave function and the Green's function are derived explicitly along with the binding energy and the spectrum of the molecular state. In the second part, we consider a thermal Boltzmann gas of fermionic molecules and compute the time-of-flight (TOF) velocity and spin distributions for a single fermion in the gas. We show that the signatures of the bound state can be observed already in the first-moment expectation values, such as TOF density and spin profiles.

We consider a dark soliton in a Bose-Einstein condensate in the presence of a weak disorder potential. Deformation of the soliton shape is analyzed within the Bogoliubov approach and by employing an expansion in eigenstates of the Pöschl-Teller Hamiltonian. Comparison of the results with the numerical simulations indicates that the linear response analysis reveals a good agreement even if the strength of disorder is of the order of the chemical potential of the system. In the second part of the paper we concentrate on the quantum nature of the dark soliton and demonstrate that the soliton may reveal Anderson localization in the presence of disorder. The Anderson-localized soliton may decay due to quasiparticle excitations induced by the disorder. However, we show that the corresponding lifetime is much longer than the condensate lifetime in a typical experiment.

Stability of solitons in parity-time ($\mathcal{PT}$)-symmetric periodic potentials (optical lattices) is analyzed in both one- and two-dimensional systems. First we show analytically that when the strength of the gain-loss component in the $\mathcal{PT}$ lattice rises above a certain threshold (phase transition point), an infinite number of linear Bloch bands turn complex simultaneously. Second, we show that while stable families of solitons can exist in $\mathcal{PT}$ lattices, increasing the gain-loss component has an overall destabilizing effect on soliton propagation. Specifically, when the gain-loss component increases, the parameter range of stable solitons shrinks as new regions of instability appear. Third, we investigate the nonlinear evolution of unstable $\mathcal{PT}$ solitons under perturbations, and show that the energy of perturbed solitons can grow unbounded even though the $\mathcal{PT}$ lattice is below the phase transition point.

In this paper, we investigate the dispersion properties of a multiatomic coupled-resonator optical waveguide (CROW), and show the existence of band-dependent group velocities in its slow-light bands. By including the next-nearest-neighbor coupling terms in a coupled-mode theory (CMT) analysis for the structure, we explain the physical origin of the band-dependent group velocities in terms of the modification of molecular mode-coupling strengths, and also derive the criteria for complete band separation and perfect intermode intensity overlap. Our results imply that when estimating the performance of a multiwave slow-light device, the band dependency of group velocities must also be considered in addition to the conventional CROW dispersion. Numerical analysis with a photonic crystal platform shows excellent agreement with theory.

It has recently been discovered that stabilization of two-dimensional (2D) solitons against the critical collapse in media with cubic nonlinearity by means of nonlinear lattices (NLs) is a challenging problem. We address the one-dimensional (1D) version of the problem, i.e., the nonlinear-Schrödinger equation (NLSE) with quintic or cubic-quintic (CQ) terms, the coefficients in front of which are periodically modulated in space. The models may be realized in optics and Bose-Einstein condensates (BECs). Stability diagrams for the solitons are produced by means of numerical methods and analytical approximations. It is found that the sinusoidal NL stabilizes solitons supported by the quintic-only nonlinearity in a narrow stripe in the respective parameter plane, contrary to the case of the cubic nonlinearity in 2D, where the stabilization of solitons by smooth spatial modulations is not possible at all. The stability region is much broader in the 1D CQ model, where higher-order solitons may be stable too.

The photonic crystal fiber (PCF) is one of the excellent media for generating photon pairs via spontaneous four-wave mixing. Here we study how the inhomogeneity of PCFs affect the spectral properties of photon pairs from both the theoretical and experimental aspects. The theoretical model shows that the photon pairs born in different places of the inhomogeneous PCF are coherently superposed, and a modulation in the broadened spectrum of phase-matching function will appear, which prevents the realization of spectral factorable photon pairs. In particular, the inhomogeneity induced modulation can be examined by measuring the spectrum of the individual signal or idler field when the asymmetric group-velocity matching condition is approximately fulfilled. Our experiments are performed by tailoring the spectrum of pulsed pump to satisfy the specified phase-matching condition. The observed spectra of individual signal photons, which are produced from different segments of the 1.9 m inhomogeneous PCF, agree with the theoretical predictions. The investigations are not only useful for fiber-based quantum state engineering, but also provide a dependable method to test the homogeneity of PCF.

A superconducting qubit coupled to a microwave resonator provides a controllable system that enables fundamental studies of light-matter interactions. In the dispersive regime, photons in the resonator exhibit induced frequency and phase shifts which are revealed in the resonator transmission spectrum measured with fixed qubit-resonator detuning. In this static detuning scheme, the phase shift is measured in the far-detuned, linear dispersion regime to avoid measurement-induced demolition of the qubit quantum state. Here we explore the qubit-resonator dispersive interaction over a much broader range of detunings, by using a dynamic procedure where the qubit transition is driven adiabatically. We use resonator Wigner tomography to monitor the interaction, revealing exotic nonlinear effects on different photon states, e.g., Fock states, coherent states, and Schrödinger cat states, thereby demonstrating a quantum Kerr effect in the dynamic framework.

It is shown that the absorbtion of a weak field in a thick resonant absorber is a reversible process even in the case of the homogeneous broadening of the absorption line. As an example, the propagation of a long rectangular pulse with sharp edges in an optically dense resonant medium is studied theoretically in the linear response approximation. Transient nutation (TN), free induction decay (FID), and transients, induced by the phase switch of the incident pulse, are considered. It is shown that in exact resonance the amplitude of FID increases with the length of the medium. FID arises due to the scattered radiation field (dipoles ringing). In a thick medium the scattered field is almost of the same amplitude but opposite in phase with the incident radiation field. Both fields interfere destructively to produce what is seen as radiation damping at the output of the medium. The scattered field needs time to develop. Therefore, the leading edge of the pulse is not absorbed, demonstrating temporal transparency followed by TN. Phase shift (180${}^{\circ }$) of the pulse brings the incident pulse in phase with the scattered radiation. Constructive interference of the pulse with the scattered radiation field produces a short pulse with an amplitude that is two times larger than the amplitude of the incident pulse. If the input pulse is detuned from resonance, for a particular detuning and optical thickness of the medium the amplitude of the transient pulse, induced by the phase shift, is nearly three times larger than the amplitude of the incident pulse. This is explained by the interference of the scattered field, the phase-shifted input field, and the slowly propagating part of the pulse, developed before the phase shift.

The upper bound of the fine-grained uncertainty relation is different for classical physics, quantum physics, and no-signaling theories with maximal nonlocality (superquantum correlation), as was shown in the case of bipartite systems [J. Oppenheim and S. Wehner, Science 330, 1072 (2010)]. Here, we extend the fine-grained uncertainty relation to the case of tripartite systems. We show that the fine-grained uncertainty relation determines the nonlocality of tripartite systems as manifested by the Svetlichny inequality, discriminating between classical physics, quantum physics, and superquantum correlations.

We investigate the possible use of Bose-Einstein condensates of diatomic molecules to measure nuclear spin-dependent parity-violation effects, outlining a detection method based on the internal Josephson effect between molecular states of opposite parity. When applied to molecular condensates, the fine experimental control achieved in atomic bosonic Josephson junctions could provide data on anapole moments and neutral weak couplings.

Unitary evolutions of a qubit are traditionally represented geometrically as rotations of the Bloch sphere, but the composition of such evolutions is handled algebraically through matrix multiplication [of SU(2) or SO(3) matrices]. Hamilton's construct, called turns, provides for handling the latter pictorially through the addition of directed great circle arcs on the unit sphere S${}^2\subset {\mathbb{R}}^3$, resulting in a non-Abelian version of the parallelogram law of vector addition of the Euclidean translation group. This construct is developed into a visual tool kit for handling the design of single-qubit unitary gates. As an application, it is shown, in the concrete case wherein the qubit is realized as polarization states of light, that all unitary gates can be realized conveniently through a universal gadget consisting of just two quarter-wave plates (QWP) and one half-wave plate (HWP). The analysis and results easily transcribe to other realizations of the qubit: The case of NMR is obtained by simply substituting $\pi /2$ and $\pi$ pulses respectively for QWPs and HWPs, the phases of the pulses playing the role of the orientation of fast axes of these plates.

We present a scheme to engineer a two-mode squeezed state of effective bosonic modes realized by collective excitations of two distant nitrogen-vacancy-center ensembles (NVEs) coupled to separated transmission line resonators (TLRs), which are interconnected by a current-biased Josephson-junction superconducting qubit. By making use of the engineered NVE-TLR magnetic coupling with Raman transition between the ground sublevels of the NVEs, we may manipulate the artificial reservoir by tuning the external driving fields. The TLR decay induces an artificial reservoir, which can drive the system to the desired entangled squeezed states. Our idea provides a scalable way to a NVE-based continuous-variable quantum-information processing, which is close to being achievable with currently available technology.

Energy-resolved studies of positron-molecule collisions exhibit vibrational Feshbach resonances in annihilation, thus providing evidence that positrons can bind to these species. The downshifts of the observed resonances from the positions of the vibrational modes provides a measure of the positron-molecule binding energies, which range from 1 to 300 meV. Reported here are annihilation spectra and binding energies for a wider range of chemical species than studied previously, including aldehydes, ketones, formates, acetates, and nitriles. While the measured binding energies show an approximate correlation with molecular dipole polarizability and permanent dipole moment, other effects are important for dipole moments $\ge$2.0 D. For these compounds, it appears that localization of the positron wave function near a portion of the molecule leads to enhanced binding and an increased dependence on both the molecular dipole moment and the electron-positron correlations. The relationship of these results to theoretical calculations is discussed.