965 research outputs found
Homogeneous spaces with symmetries
We give a brief survey of main recent results about invariant pseudo-Riemannian metrics and classical affinor structures on homogeneous spaces with symmetries obtained by the participants of the joint BRFFI-RFFI project “Homogeneous spaces with symmetries”
Charge relaxation resistance in the Coulomb blockade problem
We study the dissipation in a system consisting of a small metallic island
coupled to a gate electrode and to a massive reservoir via single tunneling
junction. The dissipation of energy is caused by a slowly oscillating gate
voltage. We compute it in the regimes of weak and strong Coulomb blockade. We
focus on the regime of not very low temperatures when electron coherence can be
neglected but quantum fluctuations of charge are strong due to Coulomb
interaction. The answers assume a particularly transparent form while expressed
in terms of specially chosen physical observables. We discovered that the
dissipation rate is given by a universal expression in both limiting cases.Comment: 21 pages, 12 figure
2,4,6-trinitrotoluene as a trigger of oxidative stress in Fagopyrum tataricum callus cells
Effect of 2,4,6-trinitrotoluene (TNT) on callus cells of Tartar buckwheat (Fagopyrum tataricum (L.) Gaertn.) was accompanied by six-electron reduction of ortho- or para-nitro groups of the xenobiotic with the production of 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT). It was discovered that the xenobiotic TNT impairs integrity of cell membrane, which apparently results from its one-electron reduction coupled with production of nitro radical-anion and superoxide anion. © 2013 Pleiades Publishing, Ltd
Improving Josephson junction reproducibility for superconducting quantum circuits: junction area fluctuation
Josephson superconducting qubits and parametric amplifiers are prominent
examples of superconducting quantum circuits that have shown rapid progress in
recent years. With the growing complexity of such devices, the requirements for
reproducibility of their electrical properties across a chip have become
stricter. Thus, the critical current variation of the Josephson junction,
as the most important electrical parameter, needs to be minimized. Critical
current, in turn, is related to normal-state resistance the Ambegaokar-Baratoff
formula, which can be measured at room temperature. Here, we focus on the
dominant source of Josephson junction critical current non-uniformity junction
area variation. We optimized Josephson junctions fabrication process and
demonstrate resistance variation of and across
and chip areas, respectively. For a
wide range of junction areas from to we
ensure a small linewidth standard deviation of measured over 4500
junctions with linear dimensions from to . The developed process
was tested on superconducting highly coherent transmon qubits and a nonlinear asymmetric inductive element parametric
amplifier
High-Q trenched aluminum coplanar resonators with an ultrasonic edge microcutting for superconducting quantum devices
Dielectric losses are one of the key factors limiting the coherence of
superconducting qubits. The impact of materials and fabrication steps on
dielectric losses can be evaluated using coplanar waveguide (CPW) microwave
resonators. Here, we report on superconducting CPW microwave resonators with
internal quality factors systematically exceeding 5x106 at high powers and
2x106 (with the best value of 4.4x106) at low power. Such performance is
demonstrated for 100-nm-thick aluminum resonators with 7-10.5 um center trace
on high-resistivity silicon substrates commonly used in quantum Josephson
junction circuits. We investigate internal quality factors of the resonators
with both dry and wet aluminum etching, as well as deep and isotropic reactive
ion etching of silicon substrate. Josephson junction compatible CPW resonators
fabrication process with both airbridges and silicon substrate etching is
proposed. Finally, we demonstrate the effect of airbridges positions and extra
process steps on the overall dielectric losses. The best quality fa ctors are
obtained for the wet etched aluminum resonators and isotropically removed
substrate with the proposed ultrasonic metal edge microcutting.Comment: 6 pages, 2 figure
The Energy Level Shifts, Wave Functions and the Probability Current Distributions for the Bound Scalar and Spinor Particles Moving in a Uniform Magnetic Field
We discuss the equations for the bound one-active electron states based on
the analytic solutions of the Schrodinger and Pauli equations for a uniform
magnetic field and a single attractive -potential. It is vary
important that ground electron states in the magnetic field differ essentially
from the analogous state of spin-0 particles, whose binding energy was
intensively studied more than forty years ago. We show that binding energy
equations for spin-1/2 particles can be obtained without using the language of
boundary conditions in the -potential model developed in pioneering
works. We use the obtained equations to calculate the energy level
displacements analytically and demonstrate nonlinear dependencies on field
intensity. We show that the magnetic field indeed plays a stabilizing role in
considered systems in a case of the weak intensity, but the opposite occurs in
the case of strong intensity. These properties may be important for real
quantum mechanical fermionic systems in two and three dimensions. We also
analyze the exact solution of the Pauli equation for an electron moving in the
potential field determined by the three-dimensional -well in the
presence of a strong magnetic field. We obtain asymptotic expressions for this
solution for different values of the problem parameters. In addition, we
consider electron probability currents and their dependence on the magnetic
field. We show that including the spin in the framework of the nonrelativistic
approach allows correctly taking the effect of the magnetic field on the
electric current into account. The obtained dependencies of the current
distribution, which is an experimentally observable quantity, can be manifested
directly in scattering processes, for example.Comment: 31 pages, 10 figure
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