Spin correlated interferometry for polarized and unpolarized photons on a beam splitter

Spin interferometry of the 4th order for independent polarized as well as unpolarized photons arriving simultaneously at a beam splitter and exhibiting spin correlation while leaving it, is formulated and discussed in the quantum approach. Beam splitter is recognized as a source of genuine singlet photon states. Also, typical nonclassical beating between photons taking part in the interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at http://m3k.grad.hr/pavici

Dispersion and fidelity in quantum interferometry

We consider Mach-Zehnder and Hong-Ou-Mandel interferometers with nonclassical states of light as input, and study the effect that dispersion inside the interferometer has on the sensitivity of phase measurements. We study in detail a number of different one- and two-photon input states, including Fock, dual Fock, N00N states, and photon pairs from parametric downconversion. Assuming there is a phase shift $\phi_0$ in one arm of the interferometer, we compute the probabilities of measurement outcomes as a function of $\phi_0$, and then compute the Shannon mutual information between $\phi_0$ and the measurements. This provides a means of quantitatively comparing the utility of various input states for determining the phase in the presence of dispersion. In addition, we consider a simplified model of parametric downconversion for which probabilities can be explicitly computed analytically, and which serves as a limiting case of the more realistic downconversion model.Comment: 12 pages, 14 figures. Submitted to Physical Review

Electrical phase change of CVD-grown Ge-Sb-Te thin film device

A prototype Ge-Sb-Te thin film phase-change memory device has been fabricated and reversible threshold and phase change switching demonstrated electrically, with a threshold voltage of 1.5 – 1.7 V. The Ge-Sb-Te thin film was fabricated by chemical vapour deposition (CVD) at atmospheric pressure using GeCl4, SbCl5, and Te precursors with reactive gas H2 at reaction temperature 780 °C and substrate temperature 250 °C. The surface morphology and composition of the CVD-grown Ge-Sb-Te thin film has been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The CVD-grown Ge-Sb-Te thin film shows promise for the phase change memory applications

Comparisons and Applications of Four Independent Numerical Approaches for Linear Gyrokinetic Drift Modes

To help reveal the complete picture of linear kinetic drift modes, four independent numerical approaches, based on integral equation, Euler initial value simulation, Euler matrix eigenvalue solution and Lagrangian particle simulation, respectively, are used to solve the linear gyrokinetic electrostatic drift modes equation in Z-pinch with slab simplification and in tokamak with ballooning space coordinate. We identify that these approaches can yield the same solution with the difference smaller than 1\%, and the discrepancies mainly come from the numerical convergence, which is the first detailed benchmark of four independent numerical approaches for gyrokinetic linear drift modes. Using these approaches, we find that the entropy mode and interchange mode are on the same branch in Z-pinch, and the entropy mode can have both electron and ion branches. And, at strong gradient, more than one eigenstate of the ion temperature gradient mode (ITG) can be unstable and the most unstable one can be on non-ground eigenstates. The propagation of ITGs from ion to electron diamagnetic direction at strong gradient is also observed, which implies that the propagation direction is not a decisive criterion for the experimental diagnosis of turbulent mode at the edge plasmas.Comment: 12 pages, 10 figures, accept by Physics of Plasma

Reversible Embedding to Covers Full of Boundaries

In reversible data embedding, to avoid overflow and underflow problem, before data embedding, boundary pixels are recorded as side information, which may be losslessly compressed. The existing algorithms often assume that a natural image has little boundary pixels so that the size of side information is small. Accordingly, a relatively high pure payload could be achieved. However, there actually may exist a lot of boundary pixels in a natural image, implying that, the size of side information could be very large. Therefore, when to directly use the existing algorithms, the pure embedding capacity may be not sufficient. In order to address this problem, in this paper, we present a new and efficient framework to reversible data embedding in images that have lots of boundary pixels. The core idea is to losslessly preprocess boundary pixels so that it can significantly reduce the side information. Experimental results have shown the superiority and applicability of our work

Magnetic Interaction between Surface Engineered Rare-earth Atomic Spins

We report the ab initio study of rare-earth adatoms (Gd) on an insulating surface. This surface is of interest because of previous studies by scanning tunneling microscopy showing spin excitations of transition metal adatoms. The present work is the first study of rare-earth spin-coupled adatoms, as well as the geometry effect of spin coupling, and the underlying mechanism of ferromagnetic coupling. The exchange coupling between Gd atoms on the surface is calculated to be antiferromagnetic in a linear geometry and ferromagnetic in a diagonal geometry, by considering their collinear spins and using the PBE+U exchange correlation. We also find the Gd dimers in these two geometries are similar to the nearest-neighbor (NN) and the next-NN Gd atoms in GdN bulk. We analyze how much direct exchange, superexchange, and RKKY interactions contribute to the exchange coupling for both geometries by additional first-principles calculations of related model systems