Tripartite entanglement from interlinked χ(2)\chi^{(2)} parametric interactions

We examine the tripartite entanglement properties of an optical system using interlinked $\chi^{(2)}$ interactions, recently studied experimentally in terms of its phase-matching properties by Bondani et al [M. Bondani, A. Allevi, E. Gevinti, A. Agliati, and A. Andreoni, arXiv:quant-ph/0604002.]. We show that the system does produce output modes which are genuinely tripartite entangled and that detection of this entanglement depends crucially on the correlation functions which are measured, with a three-mode Einstein-Podolsky-Rosen inequality being the most sensitive.Comment: 15 pages, 5 figure

Photon signature analysis using template matching

We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ? photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNP TM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly

Ground-State Properties of a Rotating Bose-Einstein Condensate with Attractive Interaction

The ground state of a rotating Bose-Einstein condensate with attractive interaction in a quasi-one-dimensional torus is studied in terms of the ratio $\gamma$ of the mean-field interaction energy per particle to the single-particle energy-level spacing. The plateaus of quantized circulation are found to appear if and only if $\gamma<1$ with the lengths of the plateaus reduced due to hybridization of the condensate over different angular-momentum states.Comment: 4 pages, 2 figures, Accepted for publication in Physical Reveiw Letter

Structural distortions and model Hamiltonian parameters: from LSDA to a tight-binding description of LaMnO_3

The physics of manganites is often described within an effective two-band tight-binding (TB) model for the Mn e_g electrons, which apart from the kinetic energy includes also a local "Hund's rule" coupling to the t_{2g} core spin and a local coupling to the Jahn-Teller (JT) distortion of the oxygen octahedra. We test the validity of this model by comparing the energy dispersion calculated for the TB model with the full Kohn-Sham band-structure calculated within the local spin-density approximation (LSDA) to density functional theory. We analyze the effect of magnetic order, JT distortions, and "GdFeO_3-type" tilt-rotations of the oxygen octahedra. We show that the hopping amplitudes are independent of magnetic order and JT distortions, and that both effects can be described with a consistent set of model parameters if hopping between both nearest and next-nearest neighbors is taken into account. We determine a full set of model parameters from the density functional theory calculations, and we show that both JT distortions and Hund's rule coupling are required to obtain an insulating ground state within LSDA. Furthermore, our calculations show that the "GdFeO_3-type" rotations of the oxygen octahedra lead to a substantial reduction of the hopping amplitudes but to no significant deviation from the simple TB model.Comment: replaced with final (published) version with improved presentatio

Spin domain formation in spinor Bose-Einstein condensation

The spatial structure of the spinor Bose-Einstein condensates with the spin degrees of freedom is analyzed based on the generalized Gross-Pitaevskii equation (GP) in the light of the present spin domain experiment on m_F=\pm 1, and 0 of the hyperfine state F=1 of ^{23}Na atom gases. The GP solutions in three- and one-spatial dimensional cases reproduce the observed spin domain structures, revealing the length scale associated with the existence of the weak interaction of the spin-spin channel, other than the ordinary coherence length related to the density-density channel. The obtained domain structure in GP is compared with the result in Thomas-Fermi approximation. The former solution is found to better describe the observed features than the latter.Comment: 9 pages, 14 figure