Methods of labor economy increasing in educational organization

The urgency of problem under investigation due to fact that increasing demand of the information technology infrastructure development in current conditions of educational institutions functioning, including formation of the information-educational environment point of view. Offered organizational and economic model of constructing processes for software development is based on agile project management, regarded as an object-oriented tool for optimizing labor economics. The purpose of article is in model for labor economy processes optimization as a part of software development based on agile project management methodology in departments associated with development of information technologies in educational organization. The leading method to the problem study is in measurement of labor economics key indicators, including specific metrics of technical expert’s human capital growth. As an experimental base of research are considered educational organizations, at different times, using classical approach for software development and agile project management. The article presents research results of educational organizations departments engaged in project activities for development of information technologies, which are in the development of software products using classical approach for software development and agile project management. Article submissions may be useful to create a culture for constructing labor economics and human capital system based on sustainable growth in departments of educational institutions working in the field of information technology. © 2016 Dorozhkin et al

Quantum spin field effect transistor

We propose, theoretically, a new type of quantum field effect transistor that operates purely on the flow of spin current in the absence of charge current. This spin field effect transistor (SFET) is constructed without any magnetic material, but with the help of spin flip mechanism provided by a rotating external magnetic field of uniform strength. The SFET generates a constant instantaneous spin current that is sensitively controllable by a gate voltage as well as by the frequency and strength of the rotating field. The characteristics of a Carbon nanotube based SFET is provided as an example

Effective low-energy theory for correlated carbon nanotubes

The low-energy theory for single-wall carbon nanotubes including Coulomb interactions is derived and analyzed. It describes two fermion chains without interchain hopping but coupled in a specific way by the interaction. The strong-coupling properties are studied by bosonization, and consequences for experiments on single armchair nanotubes are discussed.Comment: 5 pages REVTeX, includes one figur

Predicting a Gapless Spin-1 Neutral Collective Mode branch for Graphite

Using the standard tight binding model of 2d graphite with short range electron repulsion, we find a gapless spin-1, neutral collective mode branch {\em below the particle-hole continuum} with energy vanishing linearly with momenta at the $\Gamma$ and $K$ points in the BZ. This spin-1 mode has a wide energy dispersion, 0 to $\sim 2 eV$ and is not Landau damped. The `Dirac cone spectrum' of electrons at the chemical potential of graphite generates our collective mode; so we call this `spin-1 zero sound' of the `Dirac sea'. Epithermal neutron scattering experiments, where graphite single crystals are often used as analyzers (an opportunity for `self-analysis'!), and spin polarized electron energy loss spectroscopy (SPEELS) can be used to confirm and study our collective mode.Comment: 4 pages of LaTex file, 3 eps figure file

Colloquium: Trapped ions as quantum bits -- essential numerical tools

Trapped, laser-cooled atoms and ions are quantum systems which can be experimentally controlled with an as yet unmatched degree of precision. Due to the control of the motion and the internal degrees of freedom, these quantum systems can be adequately described by a well known Hamiltonian. In this colloquium, we present powerful numerical tools for the optimization of the external control of the motional and internal states of trapped neutral atoms, explicitly applied to the case of trapped laser-cooled ions in a segmented ion-trap. We then delve into solving inverse problems, when optimizing trapping potentials for ions. Our presentation is complemented by a quantum mechanical treatment of the wavepacket dynamics of a trapped ion. Efficient numerical solvers for both time-independent and time-dependent problems are provided. Shaping the motional wavefunctions and optimizing a quantum gate is realized by the application of quantum optimal control techniques. The numerical methods presented can also be used to gain an intuitive understanding of quantum experiments with trapped ions by performing virtual simulated experiments on a personal computer. Code and executables are supplied as supplementary online material (http://kilian-singer.de/ent).Comment: accepted for publication in Review of Modern Physics 201

Correlation effects of carbon nanotubes at boundaries: Spin polarization induced by zero-energy boundary states

When a carbon nanotube is truncated with a certain type of edges, boundary states localized near the edges appear at the fermi level. Starting from lattice models, low energy effective theories are constructed which describe electron correlation effects on the boundary states. We then focus on a thin metallic carbon nanotube which supports one or two boundary states, and discuss physical consequences of the interaction between the boundary states and bulk collective excitations. By the renormalization group analyses together with the open boundary bosonization, we show that the repulsive bulk interactions suppress the charge fluctuations at boundaries, and assist the spin polarization.Comment: 8 pages, 1 figur

Carbon nanotube-based quantum pump in the presence of superconducting lead

Parametric electron pump through superconductor-carbon-nanotube based molecular devices was investigated. It is found that a dc current, which is assisted by resonant Andreev reflection, can be pumped out from such molecular device by a cyclic variation of two gate voltages near the nanotube. The pumped current can be either positive or negative under different system parameters. Due to the Andreev reflection, the pumped current has the double peak structure around the resonant point. The ratio of pumped current of N-SWNT-S system to that of N-SWNT-N system (I^{NS}/I^N) is found to approach four in the weak pumping regime near the resonance when there is exactly one resonant level at Fermi energy inside the energy gap. Numerical results confirm that in the weak pumping regime the pumped current is proportional to the square of the pumping amplitude V_p, but in the strong pumping regime the pumped current has the linear relation with V_p. Our numerical results also predict that pumped current can be obtained more easily by using zigzag tube than by using armchair tube

Supersymmetry in carbon nanotubes in a transverse magnetic field

Electron properties of Carbon nanotubes in a transverse magnetic field are studied using a model of a massless Dirac particle on a cylinder. The problem possesses supersymmetry which protects low energy states and ensures stability of the metallic behavior in arbitrarily large fields. In metallic tubes we find suppression of the Fermi velocity at half-filling and enhancement of the density of states. In semiconducting tubes the energy gap is suppressed. These features qualitatively persist (although to a smaller degree) in the presence of electron interactions. The possibilities of experimental observation of these effects are discussed.Comment: A new section on electron interaction effects added and explanation on roles of supersymmetry expanded. Revtex4, 6 EPS figure file

Conductance of carbon nanotubes with disorder: A numerical study

We study the conductance of carbon nanotube wires in the presence of disorder, in the limit of phase coherent transport. For this purpose, we have developed a simple numerical procedure to compute transmission through carbon nanotubes and related structures. Two models of disorder are considered, weak uniform disorder and isolated strong scatterers. In the case of weak uniform disorder, our simulations show that the conductance is not significantly affected by disorder when the Fermi energy is close to the band center. Further, the transmission around the band center depends on the diameter of these zero bandgap wires. We also find that the calculated small bias conductance as a function of the Fermi energy exhibits a dip when the Fermi energy is close to the second subband minima. In the presence of strong isolated disorder, our calculations show a transmission gap at the band center, and the corresponding conductance is very small

Quantum computing implementations with neutral particles

We review quantum information processing with cold neutral particles, that is, atoms or polar molecules. First, we analyze the best suited degrees of freedom of these particles for storing quantum information, and then we discuss both single- and two-qubit gate implementations. We focus our discussion mainly on collisional quantum gates, which are best suited for atom-chip-like devices, as well as on gate proposals conceived for optical lattices. Additionally, we analyze schemes both for cold atoms confined in optical cavities and hybrid approaches to entanglement generation, and we show how optimal control theory might be a powerful tool to enhance the speed up of the gate operations as well as to achieve high fidelities required for fault tolerant quantum computation.Comment: 19 pages, 12 figures; From the issue entitled "Special Issue on Neutral Particles