Absolute single photoionization cross-section measurements for Se${}^{+}$ ions were performed at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the photo-ion merged-beams technique. Measurements were made at a photon energy resolution of 5.5 meV from 17.75 to 21.85 eV spanning the 4$s^2$4$p^3$ ${}^4{S}_{3/2}^{\mathrm{o}}$ ground-state ionization threshold and the ${}^2{P}_{3/2}^{\mathrm{o}}$,${}^2{P}_{1/2}^{\mathrm{o}}$,${}^2{D}_{5/2}^{\mathrm{o}}$, and${}^2{D}_{3/2}^{\mathrm{o}}$ metastable state thresholds. Extensive analysis of the complex resonant structure in this region identified numerous Rydberg series of resonances and obtained the Se${}^{2+}$ 4$s^2$4$p^{2\mathrm{\hspace{0.5em}}3}$$P_2$ and 4$s^2$4$p^{2\mathrm{\hspace{0.5em}}1}$$S_0$ state energies. In addition, particular attention was given to removing significant effects in the measurements due to a small percentage of higher-order undulator radiation.

We investigate the high-order harmonic generation in ordinary buckyball ${\mathrm{C}}_{60}$, endohedral In@C${}_{60}$ fullerene, and endohedral Sb@C${}_{60}$ fullerene by means of time-dependent density functional theory. In all cases the resonant enhancement of several high-order harmonics in the plateau region up to two orders of magnitude was predicted. Theoretical investigation of absorption spectra of ${\mathrm{C}}_{60}$ showed absorption peaks in the regions of the resonant HHG enhancement. In both endohedral fullerenes, peaks of plasmon absorption and resonance enhancement were shifted toward the corresponding atomic resonant transitions, which may be used to control the spectral distribution of groups of resonant harmonics and obtain bright attosecond pulse trains.

We propose a scheme to enhance the field-free molecular alignment by shaping the femtosecond laser pulse with cubic phase modulation. We show that the molecular alignment can be obtained adiabatically during the shaped pulse and can be revived at the full rotational periods with the same degree as that at the peak of the shaped pulse. The behavior of the molecular alignment by the shaped pulse is the same as that by the slow turn-on and rapid turn-off laser pulse. Furthermore, we show that the shaped pulse with cubic phase modulation has a slight advantage in enhancing the field-free molecular alignment by comparing it with the slow turn-on and rapid turn-off laser pulse under the same laser intensity.

We describe how rescaling experimental data obtained from cold atom density profiles can reveal signatures of quantum criticality. We identify a number of important questions which can be answered by analyzing experimental data in this manner. We show that such experiments can distinguish different universality classes and that the signatures are robust against temperature, noise, and finite system size.

We analyze the role of soliton solutions and Hamiltonian singularities in the dynamics of counterpropagating waves in a medium of finite spatial extension. The soliton solution can become unstable due to the finite extension of the system. We show that the spatiotemporal dynamics then relaxes toward a Hamiltonian singular state of a nature different than that of the soliton state. This phenomenon can be explained through a geometrical analysis of the singularities of the stationary Hamiltonian system.

The effect of the Magnus force in optical micromanipulation has been observed. An ad hoc experiment has been designed based on a one-dimensional optical trap that carries angular momentum. The observed particle dynamics reveals the occurrence of this hydrodynamic force, which is neglected in the common approach. Its measured value is larger than the one predicted by the existing theoretical models for micrometric particles and low Reynolds number, showing that the Magnus force can contribute to unconventional optohydrodynamic trapping and manipulation.

We study a spin-gas model, where $N_S$ system qubits are interacting with $N_B$ bath qubits via many-body interactions. We consider multipartite Ising interactions and show how the effect of decoherence depends on the specific coupling between the system and its environment. For instance, we analyze the influence of decoherence induced by $k$-body interactions for different values of $k$. Moreover, we study how the effect of decoherence depends on the correlation between bath qubits that are coupled to different individual system qubits and compare Markovian with non-Markovian scenarios. We derive a useful canonical form of a completely positive map that describes a class of system environment interactions with a finite size of environment correlations. As examples we consider specific quantum many-body states and investigate their evolution under different decoherence models. As a complementary investigation, we study how the coupling to the environment can be employed to generate a desired multipartite state.

We study nonclassicality in the product of the probabilities of noncommuting observables. We show that within the quantum theory, nonclassical states can provide larger probability product than classical states, so that nonclassical states approach the nonfluctuating states of the classical theory more closely than classical states. This is particularized to relevant complementary observables such as conjugate quadratures, phase and number, quadrature and number, and orthogonal angular momentum components.

We investigate quantum state transfer in $\mathit{XY}$ spin chains and propose a recursive procedure to construct the nonuniform couplings within these chains of arbitrary length in order to achieve perfect state transfer. We show that this method is capable of finding all possible coupling schemes for perfect state transfer. These schemes, without external control fields, involve analytically identified engineered couplings without the need for dynamical control. The analytical solutions provide all information for coupling design.

We study the influence of the interparticle and confining potentials on statistical correlation via the correlation coefficient and mutual information in ground and some excited states of the Moshinsky atom in position and momentum space. The magnitude of the correlation between positions and between momenta is equal in the ground state. In excited states, the correlation between the momenta of the particles is greater than between their positions when they interact through an attractive potential whereas for repulsive interparticle potentials the opposite is true. Shannon entropies, and their sums (entropic formulations of the uncertainty principle), are also analyzed, showing that the one-particle entropy sum is dependent on the interparticle potential and thus able to detect the correlation between particles.

We consider a nonlinear passive optical cavity filled with left-handed and right-handed materials and driven by a coherent injected beam. We assume that both left-handed and right-handed materials possess a Kerr focusing type of nonlinearity. We show that close to the zero-diffraction regime, high-order diffraction allows us to stabilize dark localized structures in this device. These structures consist of dips in the transverse profile of the intracavity field and do not exist without high-order diffraction. We analyze the snaking bifurcation diagram associated with these structures. Finally, a realistic estimation of the model parameters is provided.

A system of three coupled toroidal microresonators arranged in a loop configuration is studied. This setup allows light entering the resonator setup from a tapered fiber to evolve along a variety of different pathways before leaving again through the fiber. In particular, the loop configuration of the resonators allows for an evolution which we term round-trip process, in which the light evolves from one resonator sequentially through all others back to the initial one. This process renders the optical properties of the system sensitive to the phases of all coupling and scattering constants in the system. We analyze the transmission and reflection spectra, and interpret them in terms of interference between the various possible evolution pathways through the resonator system. In particular, we focus on the phase dependence of the optical properties. Finally, we discuss possible applications for this phase sensitivity induced by the round-trip process, such as the measurement of the position of a nanoparticle close to one of the resonators and the measurement of changes in the refractive index between two resonators. Our analytical results for the applications are supported by proof-of-principle calculations based on the finite-difference time-domain solution of Maxwell’s equations in two dimensions on a grid.

Authors of a recent paper [Y. K. Chembo and N. Yu, Phys. Rev. A 82, 033801 (2010)] claimed to have developed a general framework for description of nonlinear effects in whispering-gallery-mode resonators with particular focus on optical-frequency-comb generation. In this Comment we demonstrate that the author's approach contains mathematical errors affecting some of the results of the paper. Fortunately, analysis of this phenomenon using a mathematically more rigorous approach shows that the main conclusions of that paper remain intact.

In a Comment [Deych, Phys. Rev. A 84, 017801 (2011)] on our recent article [Chembo and Yu, Phys. Rev. A 82, 033801 (2010)] on Kerr comb generation in monolithic whispering-gallery-mode (WGM) resonators, the author claims that even though our main results “remain intact,” the framework of our analysis contains some mathematical errors. In this Reply, we demonstrate that the author’s criticisms and his alternative theory are incorrect, and that all the disagreeing claims come from the author’s misunderstanding of the physical system under investigation. In particular, the main conceptual error in the Comment is the confusion between evanescent and radiative coupling mechanisms for WGM resonators (in terms of $Q$ factor, this is in our case a confusion between $~$${10}^9$ and $~$${10}^{2000}$, respectively). This essential misconception leads for example the author to introduce a nonphysical $~$${10}^{2000}$ multiplicative correction factor for the laser pump power. We show in this Reply that our WGM resonators are radiatively closed (because of the quasi-infinite radiative $Q$ factor), so that the Mie scattering formalism proposed by Deych, which relies on radiative coupling, can only lead to erroneous results. We also show that the modal expansion approach in our original paper is appropriate, and all our approximations are physically well justified. We therefore stand by our modeling results, which are moreover in excellent agreement with the experiments reported in [Chembo, Strekalov, and Yu, Phys. Rev. Lett. 104, 103902 (2010)].

We study a hybrid quantum computing system using a nitrogen-vacancy center ensemble (NVE) as quantum memory, a current-biased Josephson junction (CBJJ) superconducting qubit fabricated in a transmission line resonator (TLR) as the quantum computing processor, and the microwave photons in TLR as the quantum data bus. The storage process is seriously treated by considering all kinds of decoherence mechanisms. Such a hybrid quantum device can also be used to create multiqubit $W$ states of NVEs through a common CBJJ. The experimental feasibility is achieved using currently available technology.

This paper presents a theoretical study of the DNA damage due to the effect of the composite electric fields of ${\mathrm{H}}_2$O${}^{+}$ ions produced from the irradiation of a heavy ion onto a cell. A model for atomic and molecular processes in strong electric fields is developed. It is found that the composite electric fields increase the number of events of electron-impact ionization processes. This may promote DNA damage.

The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

The high-barrier quantum tunneling regime of a Bose-Einstein condensate confined in a ring-shaped optical lattice is investigated. By means of a change of basis transformation, connecting the set of “vortex” Bloch states and a Wannier-like set of localized wave functions, we derive a generalized Bose-Hubbard Hamiltonian. In addition to the usual hopping rate terms, such a Hamiltonian takes into account interaction-driven tunneling processes, which are shown to play a principal role at high filling factors, when the standard hopping rate parameter turns out to be negative. By calculating the energy and atomic current of a Bloch state, we show that such a hopping rate must be replaced by an effective hopping rate parameter containing the additional contribution an interaction-driven hopping rate. Such a contribution turns out to be crucial at high filling factors, since it preserves the positivity of the effective hopping rate parameter. Level crossings between the energies per particle of a Wannier-like state and the superfluid ground state are interpreted as a signature of the transition to configurations with macroscopically occupied states at each lattice site.