455 research outputs found
Hyperfine-induced decoherence in triangular spin-cluster qubits
We investigate hyperfine-induced decoherence in a triangular spin-cluster for
different qubit encodings. Electrically controllable eigenstates of spin
chirality (C_z) show decoherence times that approach milliseconds, two orders
of magnitude longer than those estimated for the eigenstates of the total spin
projection (S_z) and of the partial spin sum (S_{12}). The robustness of
chirality is due to its decoupling from both the total- and individual-spin
components in the cluster. This results in a suppression of the effective
interaction between C_z and the nuclear spin bath
Kohn anomalies in momentum dependence of magnetic susceptibility of some three-dimensional systems
We study a question of presence of Kohn points, yielding at low temperatures
non-analytic momentum dependence of magnetic susceptibility near its maximum,
in electronic spectum of some three-dimensional systems. In particular, we
consider one-band model on face centered cubic lattice with hopping between
nearest and next-nearest neighbors, which models some aspects of the dispersion
of ZrZn, and the two-band model on body centered cubic lattice, modeling
the dispersion of chromium. For the former model it is shown that Kohn points
yielding maxima of susceptibility exist in a certain (sufficiently wide) region
of electronic concentrations; the dependence of the wave vectors, corresponding
to the maxima, on the chemical potential is investigated. For the two-band
model we show existence of the lines of Kohn points, yielding maximum of the
susceptibility, which position agrees with the results of band structure
calculations and experimental data on the wave vector of antiferromagnetism of
chromium.Comment: 13 pages, 9 figures. JETP, in press (2017
Spin-Electric Coupling in Molecular Magnets
We study the triangular antiferromagnet Cu in external electric fields,
using symmetry group arguments and a Hubbard model approach. We identify a
spin-electric coupling caused by an interplay between spin exchange, spin-orbit
interaction, and the chirality of the underlying spin texture of the molecular
magnet. This coupling allows for the electric control of the spin (qubit)
states, e.g. by using an STM tip or a microwave cavity. We propose an
experimental test for identifying molecular magnets exhibiting spin-electric
effects.Comment: 5 pages, 3 figure
Development of fruit diseases of microbial origin during storage at treatment with antioxidant compositions
Встановлено, що досліджувані антиоксидантні композиції пригнічували розвиток епіфітних мікроорганізмів на поверхні плодів протягом зберігання. Було зафіксовано підвищення їх стрес-толерантності. Результати експерименту доводять зменшення рівня щодобових втрат від мікробіологічних захворювань у 2…3,5 разів. Найбільший позитивний ефект при зберіганні усіх видів плодів
був отриманий при обробці композицією на основі дистинолу і лецитину
Modeling of dynamic stability of flexible ultrasonic waveguides
The article considers mathematical model intended for study of dynamic stability and parametric resonance of flexible ultrasonic waveguides for applications in technology and medicine. Considered problem is reduced to the well-known Mathieu equation applied in the theory of dynamic stability of elastic systems. Parameters of the Mathieu equation defining stability of the waveguide are determined by means of finite elements method using ANSYS software and APDL programming languag
EXPERIMENTAL MODAL ANALYSIS OF ULTRASONIC SURGICAL WAVEGUIDES USING EFFECT OF INVERSE MAGNETOSTRICTION
Experimental modal analysis (EMA) of ultrasonic waveguides is important for many applications including design of ultrasonic surgical tools. However, most of the known sensors and instruments for measuring parameters of ultrasonic vibrations are limited to the measurements on the face surface of the ultrasonic waveguide and therefore unable to determine the spatial distribution of the parameters along its length, which in turn makes it difficult to identify natural modes and shapes. The article describes EMA of ultrasonic surgical waveguides based on the effect of inverse magnetostriction. During vibration of an ultrasonic waveguide the inverse magnetostriction generates alternating magnetic field which can be detected by means of an induction coil. Spatial resolution of the measurements can be achieved by application of the sensors with flat (spiral) induction coils. The sensors used in the study have simple design and low cost making them affordable for wide circle of scientists and engineers. The results of experimental studies implemented on exemplary waveguide for ultrasonic angioplasty made of AISI 321 steel are presented and discussed. The article also discusses the methods for theoretical and experimental determination of the sensitivity of the sensors used in the study. Experimental data are validated by comparing them to the results of computer-aided modal analysis using the finite element method (FEM) and found to be in good agreement with the results of FEM modeling (relative deviation of the vibratory displacements amplitude is about 4.7 %). As it follows from the experimental data and their comparison to the results of FEM modeling, the effect of inverse magnetostriction can be efficiently used for EMA of ultrasonic waveguides
Temporal Correlations of Local Network Losses
We introduce a continuum model describing data losses in a single node of a
packet-switched network (like the Internet) which preserves the discrete nature
of the data loss process. {\em By construction}, the model has critical
behavior with a sharp transition from exponentially small to finite losses with
increasing data arrival rate. We show that such a model exhibits strong
fluctuations in the loss rate at the critical point and non-Markovian power-law
correlations in time, in spite of the Markovian character of the data arrival
process. The continuum model allows for rather general incoming data packet
distributions and can be naturally generalized to consider the buffer server
idleness statistics
Criminal and Legal Tax System Protection of the Russian Federation and the Ukraine
The comparative law analysis of criminal law protection of the tax system of the Russian Federation and the Ukraine is presented in the article; some recommendations for improvement of the Russian and Ukrainian criminal legislations have been formulated on this basis as well
Universal Quantum Computation through Control of Spin-Orbit Coupling
We propose a method for quantum computation which uses control of spin-orbit
coupling in a linear array of single electron quantum dots. Quantum gates are
carried out by pulsing the exchange interaction between neighboring electron
spins, including the anisotropic corrections due to spin-orbit coupling.
Control over these corrections, even if limited, is sufficient for universal
quantum computation over qubits encoded into pairs of electron spins. The
number of voltage pulses required to carry out either single qubit rotations or
controlled-Not gates scales as the inverse of a dimensionless measure of the
degree of control of spin-orbit coupling.Comment: 4 pages, 3 figures (minor revision, references added
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