7,367 research outputs found
Enhanced Feedback Iterative Decoding of Sparse Quantum Codes
Decoding sparse quantum codes can be accomplished by syndrome-based decoding
using a belief propagation (BP) algorithm.We significantly improve this
decoding scheme by developing a new feedback adjustment strategy for the
standard BP algorithm. In our feedback procedure, we exploit much of the
information from stabilizers, not just the syndrome but also the values of the
frustrated checks on individual qubits of the code and the channel model.
Furthermore we show that our decoding algorithm is superior to belief
propagation algorithms using only the syndrome in the feedback procedure for
all cases of the depolarizing channel. Our algorithm does not increase the
measurement overhead compared to the previous method, as the extra information
comes for free from the requisite stabilizer measurements.Comment: 10 pages, 11 figures, Second version, To be appeared in IEEE
Transactions on Information Theor
Differential expansion for link polynomials
The differential expansion is one of the key structures reflecting group
theory properties of colored knot polynomials, which also becomes an important
tool for evaluation of non-trivial Racah matrices. This makes highly desirable
its extension from knots to links, which, however, requires knowledge of the
-symbols, at least, for the simplest triples of non-coincident
representations. Based on the recent achievements in this direction, we
conjecture a shape of the differential expansion for symmetrically-colored
links and provide a set of examples. Within this study, we use a special
framing that is an unusual extension of the topological framing from knots to
links. In the particular cases of Whitehead and Borromean rings links, the
differential expansions are different from the previously discovered.Comment: 11 page
Tensor coupling effects on spin symmetry in anti-Lambda spectrum of hypernuclei
The effects of -tensor coupling on the spin
symmetry of spectra in -nucleus systems have
been studied with the relativistic mean-field theory. Taking
C+ as an example, it is found that the tensor coupling
enlarges the spin-orbit splittings of by an order of magnitude
although its effects on the wave functions of are negligible.
Similar conclusions has been observed in -nucleus of different
mass regions, including O+, Ca+ and
Pb+. It indicates that the spin symmetry in
anti-lambda-nucleus systems is still good irrespective of the tensor coupling.Comment: 12 pages, 3 figures
Characterization of carbohydrate fractions and fermentation quality in ensiled alfalfa treated with different additives
This experiment was carried out to evaluate the effects of adding fast-sile (FS), previous fermented juice (PFJ), sucrose (S) or fast-sile + sucrose (FS + S) on the fermentation characteristics and carbohydrates fractions of alfalfa silages by the Cornell net carbohydrates and proteins systems (CNCPS). Silages quality were well preserved determined by pH, lactic acid (LA), acetic acid (AA), propionic acid (PA), butyric acid (BA) and (NH3-N, % of TN). Except for the silage with no addition of (CK), all other silages were well preserved. FS + S addition showed the lowest pH and contents of AA, PA, BA, and the highest contents of LA. The contents of WSC (Water soluble carbohydrate) in all alfalfa silages decreased with the extension of ensiling time, especially in the former 15 days and decreased sharply in the first 2 days. The content of sucrose in all alfalfa silages in the residual mono and disaccharides was highest, and the content of fructose was the least. The contents of all these sugars decreased sharply in the first 2 days. The content of hemicellulose decreased during ensiling, while no obvious change on content of cellulose. The content of ADL (acid detergent lignin) in alfalfa silages increased during ensiling. The content of starch in silages reduced rapidly in the former days, and then had not obvious change.Key words: Carbohydrate fractions, alfalfa silage, additives, water soluble carbohydrate (WSC)
Improvement of the Photoelectrochemical Stability of Cu2O Photocathode by Ph—CΞC—Cu Grafting
As one of the most efficient photocathodes, Cu2O has attracted substantial attention because of its theoretically high solar-to-hydrogen (STH) efficiency. However, its applications in photoelectrochemical (PEC) fields are severely restricted by the poor stability derived from serious photocorrosion. In this work, high-quality phenylethynyl copper (Ph—CΞC—Cu) are successfully self-assembled on the surface of Cu2O photocathode by a novel photothermal method to improve its photostability. With the protection of the Ph—CΞC—Cu layer, 85% of the initial photocurrent density can be remained, while only 28% of initial photocurrent density is left on bare Cu2O photocathode prepared on a copper foam (CF) substrate. The significantly improved photostability of Cu2O photocathode by the Ph—CΞC—Cu protective layer is attributed to its strong hydrophobicity, which can efficiently inhibit the corrosion of Cu2O by the aqueous electrolyte solution due to its special crystal structure. Based on the obtained Ph—CΞC—Cu/Cu2O photocathode, a two-photoelectrode cell with excellent stability (>5 h) has also been successfully constructed for water splitting without the need of an electric bias
The 13N(d,n)14O Reaction and the Astrophysical 13N(p,g)14O Reaction Rate
N()O is one of the key reactions in the hot CNO cycle
which occurs at stellar temperatures around 0.1. Up to now, some
uncertainties still exist for the direct capture component in this reaction,
thus an independent measurement is of importance. In present work, the angular
distribution of the N()O reaction at = 8.9
MeV has been measured in inverse kinematics, for the first time. Based on the
distorted wave Born approximation (DWBA) analysis, the nuclear asymptotic
normalization coefficient (ANC), , for the ground state of
O N + is derived to be fm. The
N()O reaction is analyzed with the R-matrix approach,
its astrophysical S-factors and reaction rates at energies of astrophysical
relevance are then determined with the ANC. The implications of the present
reaction rates on the evolution of novae are then discussed with the reaction
network calculations.Comment: 17 pages and 8 figure
Thermalisation of self-interacting solar flare fast electrons
Most theoretical descriptions of the production of solar flare bremsstrahlung
radiation assume the collision of dilute accelerated particles with a cold,
dense target plasma, neglecting interactions of the fast particles with each
other. This is inadequate for situations where collisions with this background
plasma are not completely dominant, as may be the case in, for example,
low-density coronal sources. We aim to formulate a model of a self-interacting,
entirely fast electron population in the absence of a dense background plasma,
to investigate its implications for observed bremsstrahlung spectra and the
flare energy budget. We derive approximate expressions for the time-dependent
distribution function of the fast electrons using a Fokker-Planck approach. We
use these expressions to generate synthetic bremsstrahlung X-ray spectra as
would be seen from a corresponding coronal source. We find that our model
qualitatively reproduces the observed behaviour of some flares. As the flare
progresses, the model's initial power-law spectrum is joined by a lower energy,
thermal component. The power-law component diminishes, and the growing thermal
component proceeds to dominate the total emission over timescales consistent
with flare observations. The power-law exhibits progressive spectral hardening,
as is seen in some flare coronal sources. We also find that our model requires
a factor of 7 - 10 fewer accelerated electrons than the cold, thick target
model to generate an equivalent hard X-ray flux. This model forms the basis of
a treatment of self-interactions among flare fast electrons, a process which
affords a more efficient means to produce bremsstrahlung photons and so may
reduce the efficiency requirements placed on the particle acceleration
mechanism. It also provides a useful description of the thermalisation of fast
electrons in coronal sources.Comment: 9 pages, 7 figures, accepted for Astronomy & Astrophysics; this
version clarifies arguments around Eqs. (11) and (20
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