Characterizing the geometrical edges of nonlocal two-qubit gates

Nonlocal two-qubit gates are geometrically represented by tetrahedron known as Weyl chamber within which perfect entanglers form a polyhedron. We identify that all edges of the Weyl chamber and polyhedron are formed by single parametric gates. Nonlocal attributes of these edges are characterized using entangling power and local invariants. In particular, SWAP (power)alpha family of gates constitutes one edge of the Weyl chamber with SWAP-1/2 being the only perfect entangler. Finally, optimal constructions of controlled-NOT using SWAP-1/2 gate and gates belong to three edges of the polyhedron are presented.Comment: 11 pages, 4 figures, Phys. Rev. A 79, 052339 (2009

Ladder operators for isospectral oscillators

We present, for the isospectral family of oscillator Hamiltonians, a systematic procedure for constructing raising and lowering operators satisfying any prescribed `distorted' Heisenberg algebra (including the $q$-generalization). This is done by means of an operator transformation implemented by a shift operator. The latter is obtained by solving an appropriate partial isometry condition in the Hilbert space. Formal representations of the non-local operators concerned are given in terms of pseudo-differential operators. Using the new annihilation operators, new classes of coherent states are constructed for isospectral oscillator Hamiltonians. The corresponding Fock-Bargmann representations are also considered, with specific reference to the order of the entire function family in each case.Comment: 13 page

Novel magnetic phases in a Gd2Ti2O7 pyrochlore for a field applied along the [100] axis

We report on longitudinal and transverse magnetisation measurements performed on single crystal samples of Gd2Ti2O7 for a magnetic field applied along the [100] direction. The measurements reveal the presence of previously unreported phases in fields below 10 kOe in an addition to the higher-field-induced phases that are also seen for H//[111], [110], and [112]. The proposed H-T phase diagram for the [100] direction looks distinctly different from all the other directions studied previously.Comment: 4 pages, 5 figure

Rate coefficients for rovibrational transitions in H_2 due to collisions with He

We present quantum mechanical and quasiclassical trajectory calculations of cross sections for rovibrational transitions in ortho- and para-H_2 induced by collisions with He atoms. Cross sections were obtained for kinetic energies between 10^-4 and 3 eV, and the corresponding rate coefficients were calculated for the temperature range 100<T<4000 K. Comparisons are made with previous calculations.Comment: 21 pages, 2 figures, AAS, eps

Entangling characterization of (SWAP)1/m and Controlled unitary gates

We study the entangling power and perfect entangler nature of (SWAP)1/m, for m>=1, and controlled unitary (CU) gates. It is shown that (SWAP)1/2 is the only perfect entangler in the family. On the other hand, a subset of CU which is locally equivalent to CNOT is identified. It is shown that the subset, which is a perfect entangler, must necessarily possess the maximum entangling power.Comment: 12 pages, 1 figure, One more paragraph added in Introductio

FEM Analysis of Squirrel Cage Induction Motor Fed with Raised Sine Wave Supply

AC motors are used frequently for many industrial applications such as material handling, traction, electric vehicles etc. A novel non-sinusoidal modulation technique employing Raised Sine Wave (RSW) for the PWM inverter is proposed in this paper. Squared Sine Wave has a distinct advantage of reduced rate of change at zero crossing of each half cycle, and eliminates the need for dead band. An Finite Element Analysis (FEM) is carried out to study its suitability for AC Induction Motor. The results show that the operation has a constant startup torque for all load conditions, thus providing a smooth start from zero speed to full rated speed. This feature makes it most suitable for applications requiring frequent startup such as traction. The operation of the conventional Variable Frequency Drives using Conventional Sine Wave (CSW) is compared with the results obtained with RSW supply.DOI:http://dx.doi.org/10.11591/ijece.v3i2.170

A Numerical Study of Methods for Moist Atmospheric Flows: Compressible Equations

We investigate two common numerical techniques for integrating reversible moist processes in atmospheric flows in the context of solving the fully compressible Euler equations. The first is a one-step, coupled technique based on using appropriate invariant variables such that terms resulting from phase change are eliminated in the governing equations. In the second approach, which is a two-step scheme, separate transport equations for liquid water and vapor water are used, and no conversion between water vapor and liquid water is allowed in the first step, while in the second step a saturation adjustment procedure is performed that correctly allocates the water into its two phases based on the Clausius-Clapeyron formula. The numerical techniques we describe are first validated by comparing to a well-established benchmark problem. Particular attention is then paid to the effect of changing the time scale at which the moist variables are adjusted to the saturation requirements in two different variations of the two-step scheme. This study is motivated by the fact that when acoustic modes are integrated separately in time (neglecting phase change related phenomena), or when sound-proof equations are integrated, the time scale for imposing saturation adjustment is typically much larger than the numerical one related to the acoustics

A Scheme to Implement a Universal Two-Qubit Quantum Circuit using Cross-Resonance Hamiltonian

In this brief report, we propose a circuit which is locally equivalent to a recently proposed universal two-qubit quantum circuit involving two applications of special perfect entanglers (SPEs) and local y-rotations. Further, we discuss a scheme of implementation of the equivalent circuit using cross-resonance Hamiltonian. Finally, we implement the B-gate circuit using a CNOT gate and a $\sqrt{\text{CNOT}}$ gate. This requires the implementation time which is approximately 64.84% of the time required to implement the same gate using two CNOT gates.Comment: 6 pages, Research in progress, Comments are welcom

Studies on the distribution and standing crop of algae at Muthupet estuary, Tamilnadu

Studies were made on the occurrence and standing crop of algae from six localities in Muthupet estuary for a period of six months from March to August 1988. Totally 19 afgae belonging to the groups Chlorophyta, Phaeophyta, Rhodophyta and Cyanophyta were recorded. The green algae numbered more than other algae in all the stations. The biomass estimated for Gracilaria verruocsa, Hypnea valentiae and Enleromorpha spp. varied from 905 to 1220 gm/m2, 740 to 980. gm/m2 and 53 to 72 gm/m' respectively