Under the framework of the semiclassical theory, we investigate the equilibrium-state properties of a spin polarized dipolar Fermi gas through full numerical calculation. We show that the Fermi surfaces in both real and momentum spaces are stretched along the attractive direction of dipolar interaction. We further verify that the deformed Fermi surfaces can be well approximated by ellipsoids. In addition, the deformation parameters slightly depend on the local real- and momentum-space densities. We also study the interaction strength dependence of the energy and real- and momentum-space densities. By comparing them with variational results, we find that the ellipsoidal ansatz usually generates accurate results for weak dipolar interaction, while under strong dipolar interaction limit, notable discrepancy can be observed. Finally, we map out the stability boundary of the system.

In this paper, the non-Markovian dissipative dynamics of the phase-damped Jaynes-Cummings model in the presence of a classical homogeneous gravitational field will be analyzed. The model consists of a moving two-level atom simultaneously exposed to the gravitational field and a single-mode traveling radiation field in the presence of a non-Markovian phase damping mechanism. First, the non-Markovian master equation for the reduced density operator of the system in terms of a Hamiltonian describing the atom-field interaction in the presence of a homogeneous gravitational field will be presented. Then, the superoperator technique will be generalized and an exact solution of the non-Markovian master equation will be obtained. Assuming that initially the radiation field is prepared in a Glauber coherent state and the two-level atom is in the excited state, the influence of gravity on the temporal evolution of collapses and revivals of the atomic population inversion, atomic dipole squeezing, and photon counting statistics of the radiation field in the presence of the non-Markovian phase damped will be investigated.

We consider here the situation of a Gaussian pulse that probes a medium exhibiting two close resonance lines. We study the spatial behavior of the light pulse and emphasize some overlooked features. Moreover, for long pulses and a fast-light medium, we show that the spatial distortion of the pulse due to residual gain at the central laser wavelength cannot be reduced without enhancing another distortion effect due to spectral wing amplification.

We demonstrate experimentally the efficient fusion neutron generation from Coulomb explosion (CE) of laser irradiated large-size heteronuclear deuterated methane clusters. A conversion efficiency of $2.1\times {10}^6\text{neutrons}/\text{J}$ of incident laser energy is obtained with a 120 mJ, 70 fs laser pulse. It is 50 times higher than that of homonuclear deuterium clusters of similar size. This enhancement is attributed to the significant increase in the deuteron kinetic energies by fourfold due to energetic boosting and overrun effects during CE of heteronuclear clusters. The yield of $5.5\times {10}^6$ neutrons per pulse is obtained with a 100 TW, 50 fs driving laser pulse at an intensity of $1.5\times {10}^{19}\text{W}/{\text{cm}}^2$. This work may facilitate the development of a high-flux table-top neutron source.

We present an approach to explore and control nonlinear interactions between two orthogonally polarized femtosecond filaments launched parallel in air. The self-phase and cross-phase modulations due to the Kerr effect and cross-(de)focusing induced by the plasma and molecular alignment were distinctly identified resulting in attraction and repulsion of parallel filaments with different spatiotemporal proximities. Their interaction ranges were analyzed by comparing the interaction-induced displacements of parallel filaments at different initial separations. As proved by field-free displacements of parallel filaments around the impulsive rotational Raman excitation of the diatomic molecules in air, the molecular alignment exhibited a relatively longer interaction range than that of the plasma defocusing and the Kerr effect.

Photoionization of the $2s$ inner shell of several atomic systems belonging to the Mg $\left(Z=12\right)$ and Ar $\left(Z=18\right)$ isonuclear sequences (Mg, ${\text{Mg}}^{2+}$, ${\text{Mg}}^{8+}$, Ar, ${\text{Ar}}^{6+}$, ${\text{Ar}}^{8+}$) is investigated using the relativistic random-phase approximation and also the relativistic random-phase approximation modified to include the relaxation of atomic core. Comparison of results obtained using these two approximations reveals an important effect of relaxation, namely, that inner-shell photoionization, particularly for neutral atoms and low-charge ions, can be quite sensitive to the removal of outer electrons, contrary to what is generally believed.

We present an approach to dynamic decoherence control of finite-temperature Bose-Einstein condensates in a double-well potential. Due to the many-body interactions the standard “echo” control method becomes less effective. The approach described here takes advantage of the interaction-induced change of the spectrum, to obtain the optimal rate of $\pi$ flips of the relative phase between maximally distinguishable collective states. This method is particularly useful for probing and diagnosing the decoherence dynamics.

We discuss analytic approximations to the ground-state phase diagram of the homogeneous Jaynes-Cummings-Hubbard (JCH) Hamiltonian with general short-range hopping. The JCH model describes, e.g., radial phonon excitations of a linear chain of ions coupled to an external laser field tuned to the red motional sideband with Coulomb-mediated hopping or an array of high-$Q$ coupled cavities containing a two-level atom and photons. Specifically, we consider the cases of a linear array of coupled cavities and a linear ion chain. We derive approximate analytic expressions for the boundaries between Mott-insulating and superfluid phases and give explicit expressions for the critical value of the hopping amplitude within the different approximation schemes. In the case of an array of cavities, which is represented by the standard JCH model, we compare both approximations to numerical data from density-matrix renormalization-group calculations.

We propose and investigate an optical scheme for probabilistic implementation of an arbitrary single-mode quantum operation that can be expressed as a function of photon number operator. The scheme coherently combines multiple photon addition and subtraction and is feasible with current technology. As concrete examples, we demonstrate that the device can perform approximate noiseless linear amplification of light and can emulate Kerr nonlinearity.

The dynamical symmetry algebra of the two-dimensional Dirac Hamiltonian with equal scalar and vector Smorodinsky-Winternitz potentials is constructed. It is the Higgs algebra, a cubic polynomial generalization of SU(2). With the help of the Casimir operators, the energy levels are derived algebraically.

Making use of the master equation and effective Hamiltonian approach, we investigate the steady-state entanglement in a three-qubit $XX$ model. Both symmetric and nonsymmetric qubit-qubit couplings are considered. The system (the three qubits) is coupled to two bosonic baths at different temperatures. We calculate the steady state by the effective Hamiltonian approach and discuss the dependence of the steady-state entanglement on the temperatures and couplings. The results show that for symmetric qubit-qubit couplings, the entanglements between the nearest neighbors are equal, independent of the temperatures of the two baths. The maximum of the entanglement arrives at $T_L=T_R$. For nonsymmetric qubit-qubit couplings, however, the situation is totally different. The baths at different temperatures would benefit the entanglement and the entanglements between the nearest neighbors are no longer equal. By examining the probability distribution of each eigenstate in the steady state, we present an explanation for these observations. These results suggest that the steady entanglement can be controlled by the temperature of the two baths.

Jaynes-Cummings model is a typical model in quantum optics and has been realized with various physical systems [e.g, cavity quantum electrodynamics (QED), trapped ions, circuit QED, etc.] of two-level atoms interacting with quantized bosonic fields. Here, we propose an implementation of this model by using a single classical laser beam to drive an electron floating on liquid helium. Two lowest levels of the vertical motion of the electron act as a two-level “atom” and the quantized vibration of the electron along one of the parallel directions, e.g., $x$ direction, serves as the bosonic mode. These two degrees of freedom of the trapped electron can be coupled together by using a classical laser field. If the frequencies of the applied laser fields are properly set, the desirable Jaynes-Cummings models could be effectively realized.

The interaction energy due to electromagnetic field fluctuations between two infinitely long straight parallel dielectric-diamagnetic cylinders immersed in a medium is considered. We make use of the mode summation method for the calculations. We investigate the energy dependence on the cylindrical radial curvature and dielectric response of the involved materials. It is shown that the sign of the interaction energy can be changed by a suitable choice of the dielectric properties of the involved objects. The condition for the relation of the material’s dielectric properties for repulsive interaction is obtained to be the same as the one for planar materials.

In this paper, we address the issue of the generation of nondegenerate cross-polarization-entangled photon pairs using type-II periodically poled lithium niobate. We show that, by an appropriate engineering of the quasi-phase-matching grating, it is possible to simultaneously satisfy the conditions for two spontaneous parametric down-conversion processes, namely, ordinary pump photon down conversion to either extraordinary signal and ordinary idler paired photons or to ordinary signal and extraordinary idler paired photons. In contrast to single type-II phase matching, these two processes, when enabled together, can lead to the direct production of cross-polarization-entangled states for nondegenerate signal and idler wavelengths. Such a scheme should be of great interest in applications requiring polarization-entangled nondegenerate paired photons with, for instance, one of the entangled photons at an appropriate wavelength being used for local operation or for quantum storage in an atomic ensemble and the other one at the typical wavelength of 1550 nm for propagation through an optical fiber.

A fully relativistic time-dependent close-coupling method is developed based on Dirac’s covariant formulation of quantum mechanics. The expansion of a one-electron wave function in spin-orbit eigenfunctions yields the well-known coupled Dirac equations in two radial wave functions, while the expansion of a two-electron wave function in coupled spin-orbit eigenfunctions yields close-coupled Dirac equations in four radial wave functions. The time-dependent Dirac equations are solved directly using numerical methods that avoid the Fermi doubling pathology. Test calculations are carried out using the one-electron coupled equations for $j=\frac{1}{2}$ elastic potential scattering from ${\text{Ne}}^{9+}$ at 2.00 keV and using the two-electron close-coupled equations for $J=0,1$ ionization of ${\text{Ne}}^{9+}$ at 4.15 keV.

Using a three-dimensional quasiclassical technique we explore molecular double ionization by a linearly polarized, infrared (800 nm), and ultrashort (6 fs) laser pulse. We first focus on intensities corresponding to the tunneling regime and identify the main ionization mechanisms in this regime. We devise a selection of observables, such as the correlated momenta and the sum of the momenta parallel to the laser field as a function of the interelectronic angle of escape, where all the main mechanisms have distinct traces. Second, we address intensities above but close to the over-the-barrier intensity regime. We find a surprising anticorrelation of electron momenta similar to the experimental observations reported in Phys. Rev. Lett. 101, 053001 (2008) There, however, the anticorrelation was observed in very low intensities corresponding to the multiphoton regime. We discuss the mechanism responsible for the antiparallel two-electron escape.

We analyze vortex nucleation in mesoscopic two-dimensional Bose superfluid in a rotating trap. We explicitly include a weakly anisotropic stirring potential, breaking thus explicitly the axial symmetry. As the rotation frequency passes the critical value ${\Omega }_c$, the system undergoes an extra symmetry change or breaking. Well below ${\Omega }_c$, the ground state is properly described by the mean-field theory with an even condensate wave function. Well above ${\Omega }_c$, the mean-field solution works also well, but the order parameter becomes odd. This phenomenon involves therefore a discrete parity symmetry breaking. In the critical region, the mean-field solutions exhibit dynamical instability. The true many-body state is a strongly correlated entangled state involving two macroscopically occupied modes (eigenstates of the single-particle density operator). We characterize this state in various aspects: (i) the eligibility for adiabatic evolution, (ii) its analytical approximation given by the maximally entangled combination of two single modes, and finally (iii) its appearance in particle detection measurements.

We present a fully quantum many-body treatment of dark solitons formed by ultracold bosonic atoms in one-dimensional optical lattices. Using time-evolving block decimation to simulate the single-band Bose-Hubbard Hamiltonian, we consider the quantum dynamics of density and phase engineered dark solitons as well as the quantum evolution of mean-field dark solitons injected into the quantum model. The former approach directly models how one may create quantum entangled dark solitons in experiment. While we have already presented results regarding the latter approach elsewhere [R. V. Mishmash and L. D. Carr, Phys. Rev. Lett. 103, 140403 (2009)], we expand upon those results in this work. In both cases, quantum fluctuations cause the dark soliton to fill in and may induce an inelasticity in soliton-soliton collisions. Comparisons are made to the Bogoliubov theory which predicts depletion into an anomalous mode that fills in the soliton. Our many-body treatment allows us to go beyond the Bogoliubov approximation and calculate explicitly the dynamics of the system’s natural orbitals.

In experiments with spontaneous parametric down conversion the near-field plane is usually defined as the output facet of the generating crystal. Experimentally, however, the spatial correlations are accessed via an imaging system and observed in a region around the image of the output facet. We show that the imaged two-photon field has a very rich transverse and longitudinal structure, which is determined by the phase-matching conditions. We observe many intriguing three-dimensional structures that demonstrate the presence of spatial antibunching, an extreme localization of twin photons, and spatial correlations that resemble Bessel beams in propagation. We link these observations with previous results in second harmonic generation and predict the presence of fourth-order phase singularities. Both experiments and theory are presented, yielding further insight into the nature of the two-photon field.

We present a numerical study of quantum turbulence within the three-dimensional Gross-Pitaevskii equation, concentrating on the direct energy cascade in the case of a forced-dissipated system. We show that the behavior of the system is very sensitive to the properties of the model at the scales greater than the forcing scale, and we identify three different regimes: (1) a nonstationary regime with condensation and transition from a four-wave to a three-wave interaction process when the largest scales are not dissipated, (2) a steady weak wave turbulence regime when largest scales are dissipated with a friction-type dissipation, and (3) a state with a scale-by-scale balance of the linear and the nonlinear time scales when the large-scale dissipation is a hypoviscosity.