4,777 research outputs found
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
-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 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
- …