1,576 research outputs found
Measure of decoherence in quantum error correction for solid-state quantum computing
We considered the interaction of semiconductor quantum register with noisy
environment leading to various types of qubit errors. We analysed both phase
and amplitude decays during the process of electron-phonon interaction. The
performance of quantum error correction codes (QECC) which will be inevitably
used in full scale quantum information processors was studied in realistic
conditions in semiconductor nanostructures. As a hardware basis for quantum bit
we chose the quantum spatial states of single electron in semiconductor coupled
double quantum dot system. The modified 5- and 9-qubit quantum error correction
(QEC) algorithms by Shor and DiVincenzo without error syndrome extraction were
applied to quantum register. 5-qubit error correction procedures were
implemented for Si charge double dot qubits in the presence of acoustic phonon
environment. Chi-matrix, Choi-Jamiolkowski state and measure of decoherence
techniques were used to quantify qubit fault-tolerance. Our results showed that
the introduction of above quantum error correction techniques at small phonon
noise levels provided quadratic improvement of output error rates. The
efficiency of 5-qubits quantum error correction algorithm in semiconductor
quantum information processors was demonstrated
Half-Twisted Correlators from the Coulomb Branch
We compute correlators of chiral operators in half-twisted (0,2)
supersymmetric gauged linear sigma models. Our results give simple algebraic
formulas for a (0,2) generalization of genus zero Gromov-Witten invariants of
compact toric varieties. We derive compact expressions for deformed quantum
cohomology relations and apply our general method to several examples.Comment: 21 pages, LaTex; typos corrected; some discussion adde
Prospects for the development of advanced grain processing in Russia
Purpose: The article is devoted to the identifying and evaluating promising areas of advanced grain and legumes processing development as a strategically important area for import substitution and food security of the agribusiness complex. Methodology/Approach: To achieve this goal, it is necessary to solve the following tasks: the analysis of advanced grain and legumes processing products; the evaluation of the current Russian market for advanced grain processing products; the identification of promising products and directions of the advanced grain processing industry development. Findings: According to the analysis in this article, this industry is in its infancy, despite the fact that in most developed countries of the world, advanced grain processing is widely elaborated. The key reasons for the Russia's lag there involve the lack of domestic techniques and highly qualified specialists in this field. Processing grain into flour, starches, glucose syrups, biofuels and organic acids makes possible manufacturing plastic and other products. To realize the Russia's potential in manufacturing high-value-added agricultural products, it is necessary to provide state support for investment projects for wheat deep processing through preferential lending and taxation, and co-financing of projects. The strategic goal of the Russian agribusiness in the medium and long term should be changing the structure of manufacturing and export in order to export finished products, but not raw materials. Practical implications: The results of this research could be introduced in the process of strategic planning of the agribusiness development and import substitution policy in Russia. Originality/Value: The key contribution of this study lies in the findings of the advanced grain processing industries’ analysis in Russia with the regional aspects taken into account.peer-reviewe
A-Model Correlators from the Coulomb Branch
We compute the contribution of discrete Coulomb vacua to A-Model correlators
in toric Gauged Linear Sigma Models. For models corresponding to a compact
variety, this determines the correlators at arbitrary genus. For non-compact
examples, our results imply the surprising conclusion that the quantum
cohomology relations break down for a subset of the correlators.Comment: 27 pages, 1 xy-pic figur
High-resolution radio imaging of two luminous quasars beyond redshift 4.5
Context. Radio-loud active galactic nuclei in the early Universe are rare.
The quasars J0906+6930 at redshift z=5.47 and J2102+6015 at z=4.57 stand out
from the known sample with their compact emission on milliarcsecond (mas)
angular scale with high (0.1-Jy level) flux densities measured at GHz radio
frequencies. This makes them ideal targets for very long baseline
interferometry (VLBI) observations. Aims. By means of VLBI imaging we can
reveal the inner radio structure of quasars and model their brightness
distribution to better understand the geometry of the jet and the physics of
the sources. Methods. We present sensitive high-resolution VLBI images of
J0906+6930 and J2102+6015 at two observing frequencies, 2.3 and 8.6 GHz. The
data were taken in an astrometric observing programme involving a global
five-element radio telescope array. We combined the data from five different
epochs from 2017 February to August. Results. For one of the highest redshift
blazars known, J0906+6930, we present the first-ever VLBI image obtained at a
frequency below 8 GHz. Based on our images at 2.3 and 8.6 GHz, we confirm that
this source has a sharply bent helical inner jet structure within ~3 mas from
the core. The quasar J2102+6015 shows an elongated radio structure in the
east-west direction within the innermost ~2 mas that can be described with a
symmetric three-component brightness distribution model at 8.6 GHz. Because of
their non-pointlike mas-scale structure, these sources are not ideal as
astrometric reference objects. Our results demonstrate that VLBI observing
programmes conducted primarily with astrometric or geodetic goals can be
utilized for astrophysical purposes as well.Comment: 8 pages, 3 figures, accepted for publication in Astronomy &
Astrophysic
Models of G time variations in diverse dimensions
A review of different cosmological models in diverse dimensions leading to a
relatively small time variation of the effective gravitational constant G is
presented. Among them: 4-dimensional general scalar-tensor model,
multidimensional vacuum model with two curved Einstein spaces, multidimensional
model with multicomponent anisotropic "perfect fluid", S-brane model with
scalar fields and two form field etc. It is shown that there exist different
possible ways of explanation of relatively small time variation of the
effective gravitational constant G compatible with present cosmological data
(e.g. acceleration): 4-dimensional scalar-tensor theories or multidimensional
cosmological models with different matter sources. The experimental bounds on
G-dot may be satisfied ether in some restricted interval or for all allowed
values of the synchronous time variable.Comment: 27 pages, Late
Lidar investigations of M-zone
The creation of pulse dye lasers tuned to resonant line of meteor produced admixtures of atmospheric constituents has made it possible to begin lidar investigations of the vertical distribution of mesospheric sodium concentration and its dynamics in the upper atmosphere. The observed morning increase of sodium concentration in the vertical column is probably caused by diurnal variations of sporadic meteors. The study of the dynamics of the sodium column concentration in the period of meteor streams activity confirms the suggestion of cosmic origin of these atoms. The short lived increase of sodium concentration brought about by a meteor stream, however, exceeds by one order the level of the sporadic background
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