We study the phase separation of a spin-polarized Fermi gas with spin-orbit coupling near a wide Feshbach resonance. As a result of the competition between spin-orbit coupling and population imbalance, the phase diagram for a uniform gas develops a rich structure of phase separation involving topologically nontrivial gapless superfluid states. We then demonstrate the phase separation induced by an external trapping potential and discuss the optimal parameter region for the experimental observation of the gapless superfluid phases.

We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

We propose a single observable to witness the nonzero quantum discord of an unknown quantum state provided that we have four copies of the state. The expectation value of this observable provides a necessary and sufficient condition for the nonzero quantum discord in $2\times N$ systems and a necessary condition in higher finite-dimensional bipartite systems. Furthermore, a nontrivial lower bound of the quantum discord can be obtained from this expectation value. The proposed observable can be experimentally measured in exactly the same way as the entanglement witness. Moreover, a quantum circuit is designed to determine the expectation value of our observable with four simultaneous local qubit measurements.

We study the autoresonant dynamics of a discrete level coupled to a continuum, and show that passing adiabatically through a linear resonance, above a well-defined threshold, yields a transition to nonlinear phase locking and linear non-Markovian decay to the continuum. This process results in broadening of the population of the continuum modes beyond its natural linewidth. This concept can be employed to alter spontaneous emission, where driving an atom into phase locking with continuum modes will yield the emission of short pulses.

We study the dynamics of a chain of interacting quantum particles affected by an individual or collective environment(s), focusing on the role played by the environmental quantum correlations over the evolution of the chain. The presence of entanglement in the state of the environment magnifies the non-Markovian nature of the chain’s dynamics, giving rise to structures in figures of merit such as spin entanglement and purity that are not observed under a separable environmental state. Our analysis can be relevant to problems tackling the open-system dynamics of biological complexes of strong current interest.

We use the numerical optimization techniques of Uskov et al. [Phys. Rev. A 81, 012303 (2010)] to investigate the behavior of the success rates for Knill-Laflamme-Milburn-style [Knill et al., Nature (London) 409, 46 (2001)] two- and three-qubit entangling gates. The methods are first demonstrated at perfect fidelity and then extended to imperfect gates. We find that as the perfect fidelity condition is relaxed, the maximum attainable success rates increase in a predictable fashion depending on the size of the system, and we compare that rate of increase for several gates.

Tampering of a sample with a layer of another material is a promising technique to slow down the expansion dynamics within laser irradiated samples, with sound implications for single-particle diffraction imaging. Ideally, if an imaged object is covered by a layer of another material, during the irradiation this layer will be primarily ionized and will expand fast due to Coulomb repulsion, whereas the object located within the net neutral core will expand more slowly (hydrodynamically). We investigate the details of the electronic damage within the tampered samples during their irradiation with an intense extreme ultraviolet (EUV) pulse. We study heterogeneous clusters composed of noble gas atoms, Xe and Ar, for which chemical-bond effects can be neglected. Using a fully nonequilibrium kinetic equation code, we demonstrate the influence of cluster composition on ionization dynamics; in particular, on the electronic damage. The results are obtained for the wavelength of 32 nm, which is available at the free-electron laser in Hamburg (FLASH) facility, but our conclusions can also have implications for samples with a more complex structure and irradiated at a much shorter wavelength.

The ionization dynamics of circular Rydberg states in strong circularly polarized infrared (800 nm) laser fields is studied by means of numerical simulations with the time-dependent Schrödinger equation. We find that at certain intensities, related to the radius of the Rydberg states, atomic stabilization sets in, and the ionization probability decreases as the intensity is further increased. Moreover, there is a strong dependence of the ionization probability on the rotational direction of the applied laser field, which can be understood from a simple classical analogy.

We investigate quantum beat oscillations in the photoionization continuum of Ne atoms that are photoionized by absorption of two photons via a group of excited bound states using ultrashort extreme ultraviolet and infrared laser pulses. The extreme ultraviolet pulse starts an excited-state wave packet that is photoionized by a high-intensity infrared pulse after a variable time delay. We analyze the continuum quantum beats from this two-step photoionization process and their dependence on the photoelectron kinetic energy. We find a pronounced dependence of the quantum beat amplitudes on the photoelectron kinetic energy. The dependence changes significantly with the applied infrared laser-pulse intensity. The experimental results are in good qualitative agreement with a model calculation that is adapted to the experimental situation. It accounts for the intensity dependence of the quantum beat structure through the coupling of the excited-state wave packet to other bound Ne states induced by the high-intensity infrared laser pulse.

We investigate the absorption of two identical photons from the ground state of hydrogen-like atoms over an energy range that extends beyond that explored up to now. Our approach is based on a hybrid formula, valid in second-order perturbation theory, in which the ${\mathbf{A}}^2$ contribution from the nonrelativistic Hamiltonian is treated exactly, while the $\mathbf{A}·\mathbf{P}$ contribution is calculated in dipole approximation. We find that, at least up to 50 keV, the nonrelativistic dipole approximation, based only on the $\mathbf{A}·\mathbf{P}$ contribution, determines the values of the total cross section. Our numerical results, covering photon energies from 90 nm (13.7 eV) to 0.0248 nm (50 keV) are in very good agreement with most previous theoretical works. Differences with recent results are discussed.

The strong coupling between two autoionizing states in helium is studied theoretically with the pump-probe scheme. An isolated 100-as XUV pulse is used to excite helium near the $2s2p{(}^{1}P)$ resonance state in the presence of an intense infrared (IR) laser. The laser field introduces strong coupling between $2s2p{(}^{1}P)$ and $2p^2{(}^{1}S)$ states. The IR also can ionize helium from both autoionizing states. By changing the time delay between the XUV and the IR pulses, we investigated the photoelectron spectra near the two resonances. The results are used to explain the recent experiment by Gilbertson et al. [Phys. Rev. Lett. 105, 263003 (2010)]. Using the same isolated attosecond pulse and a 540-nm laser, we also investigate the strong coupling between $2s2p{(}^{1}P)$ and $2s^2{(}^{1}S)$ by examining how the photoelectron spectra are modified versus the time delay and the possibility of observing Autler-Townes doublet in such experiments.

The effects of Doppler broadening on Autler-Townes (AT) splitting in six-wave mixing (SWM) are investigated by the dressed-state model. We analyze the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting and find that, depending on the wave-number ratio, there may be two resonant velocities which can originate from resonance with one of the dressed states or from resonance with two different dressed states. Based on this model, we discuss a novel type of AT doublet in the SWM spectrum, where macroscopic effects play an important role. Specifically, the existence of resonant peaks requires polarization interference between atoms of different velocities in addition to a change in the number of resonant atoms involved. Our model can also be employed to analyze electromagnetically induced transparency resonance and other types of Doppler-free high-resolution AT spectroscopy.

The most simple and seemingly straightforward application of the photon blockade effect, in which the transport of one photon prevents the transport of others, would be to separate two incoming indistinguishable photons to different output ports. We show that time-energy uncertainty relations inherently prevent this ideal situation when the blockade is implemented by a two-level system. The fundamental nature of this limit is revealed in the fact that photon blockade in the strong coupling regime of cavity QED, resulting from the nonlinearity of the Jaynes-Cummings energy level structure, exhibits efficiency and temporal behavior identical to those of photon blockade in the bad cavity regime, where the underlying nonlinearity is that of the atom itself. We demonstrate that this limit can be exceeded, yet not avoided, by exploiting time-energy entanglement between the incident photons. Finally, we show how this limit can be circumvented completely by using a three-level atom coupled to a single-sided cavity, enabling an ideal and robust photon routing mechanism.

We theoretically demonstrate a variety of multipole plasmonic lattice solitons, including dipoles, quadrupoles, and necklaces, in two-dimensional metallic nanowire arrays with Kerr-type nonlinearities. Such solitons feature complex internal structures with an ultracompact mode size approaching or smaller than one wavelength. Their mode sizes and the stability characteristics are studied in detail within the framework of coupled mode theory. The conditions to form and stabilize these highly confined solitons are within the experimentally achievable range.

The metastable $H{}^3{\Delta }_1$ state in the thorium monoxide (ThO) molecule is highly sensitive to the presence of a $CP$-violating permanent electric dipole moment of the electron (eEDM) [E. R. Meyer and J. L. Bohn, Phys. Rev. A 78, 010502 (2008)]. The magnetic dipole moment ${\mu }_H$ and the molecule-fixed electric dipole moment $D_H$ of this state are measured in preparation for a search for the eEDM. The small magnetic moment ${\mu }_H=8.5\left(5\right)\times {10}^{-3}{\mu }_B$ displays the predicted cancellation of spin and orbital contributions in a ${}^3{\Delta }_1$ paramagnetic molecular state, providing a significant advantage for the suppression of magnetic field noise and related systematic effects in the eEDM search. In addition, the induced electric dipole moment is shown to be fully saturated in very modest electric fields (<10 V/cm). This feature is favorable for the suppression of many other potential systematic errors in the ThO eEDM search experiment.

In this work, we perform a study on high-lying $S$-wave resonances in Ps-H scattering below the $e^{+}$-H${}^{-}$ threshold. The method of complex-coordinate rotation is applied together with highly correlated wave functions containing all six interparticle distances. Using such Hylleraas bases up to 6412 terms, the energy positions up to the 8$S$ state and the widths up to the 7$S$ state in the Rydberg series converging to the H${}^{-}$ threshold are determined. The energies of 4$S$ to 7$S$ states from the present calculations are fitted into the quantum defect formula, from which the energies of higher members in the Rydberg series can be deduced.

The (nonrelativistic) Abraham-Lorentz equation of motion for a point electron, while suffering from runaway solutions and an acausal response to external forces, is compatible with the optical theorem. We show that a nonrelativistic theory of radiative reaction that allows for a finite charge distribution is not only causal and free of runaway solutions but also consistent with the optical theorem and the standard formulas for the Rayleigh and Thomson scattering cross sections.

Seo et al. [Phys. Rev. A 81, 053824 (2010)] have studied the interaction of a TEM${}_{10}$ mode in a cavity-QED microlaser. They claim that this scheme represents an experimental realization of an atomic Šolc filter proposed by Hong et al. [Opt. Express 17, 15455 (2009)]. Even if the regime of interaction considered is nonperturbative, we point out that this statement is valid only for a small range of intensity and is misleading in the general case of an arbitrarily strong field where the effect is related to the nonadiabatic jump phenomenon [G. S. Vasilev and N. V. Vitanov, Phys. Rev. A 73, 023416 (2006)].

In this reply to the Comment by Bouchene et al. [Phys. Rev. A 84, 037801 (2011)], we show that our experiment [Phys. Rev. A 81, 053824 (2010)] was a legitimate demonstration of the atomic $\check{\text{S}}$olc filter for the range of parameters that we have studied. The more detailed theoretical framework presented in the Comment and the interpretation of its outcome in terms of nonadiabatic jump are only necessary for larger field intensities.