310 research outputs found
Experimental state control by fast non-Abelian holonomic gates with a superconducting qutrit
Quantum state manipulation with gates based on geometric phases acquired
during cyclic operations promises inherent fault-tolerance and resilience to
local fluctuations in the control parameters. Here we create a general
non-Abelian and non-adiabatic holonomic gate acting in the
subspace of a three-level transmon fabricated in a fully coplanar design.
Experimentally, this is realized by simultaneously coupling the first two
transitions by microwave pulses with amplitudes and phases defined such that
the condition of parallel transport is fulfilled. We demonstrate the creation
of arbitrary superpositions in this subspace by changing the amplitudes of the
pulses and the relative phase between them. We use two-photon pulses acting in
the holonomic subspace to reveal the coherence of the state created by the
geometric gate pulses and to prepare different superposition states. We also
test the action of holonomic NOT and Hadamard gates on superpositions in the
subspace
Comment on "New modes of halo excitations in the 6He nucleus"
We try to explain the differences in the 6He dipole strength function in
refs. [1] and [2]. We perform the full basis calculation of the strength
function with the same renormalized interaction as in [1] and show that the
size of the basis, needed for converged calculations of the 6He continuum
spectrum, is much larger than that for the discrete spectrum. The renormalized
interaction of [1] therefore cannot be used for the continuum spectrum
calculations with the same basis as for the ground state.Comment: 2 pages, 3 figure
Two-proton radioactivity and three-body decay. III. Integral formulae for decay widths in a simplified semianalytical approach
Three-body decays of resonant states are studied using integral formulae for
decay widths. Theoretical approach with a simplified Hamiltonian allows
semianalytical treatment of the problem. The model is applied to decays of the
first excited state of Ne and the ground state of
Fe. The convergence of three-body hyperspherical model calculations to
the exact result for widths and energy distributions are studied. The
theoretical results for Ne and Fe decays are updated and
uncertainties of the derived values are discussed in detail. Correlations for
the decay of Ne state are also studied.Comment: 19 pages, 20 figure
Halo Excitation of He in Inelastic and Charge-Exchange Reactions
Four-body distorted wave theory appropriate for nucleon-nucleus reactions
leading to 3-body continuum excitations of two-neutron Borromean halo nuclei is
developed. The peculiarities of the halo bound state and 3-body continuum are
fully taken into account by using the method of hyperspherical harmonics. The
procedure is applied for A=6 test-bench nuclei; thus we report detailed studies
of inclusive cross sections for inelastic He(p,p')He and
charge-exchange Li(n,p)He reactions at nucleon energy 50 MeV. The
theoretical low-energy spectra exhibit two resonance-like structures. The first
(narrow) is the excitation of the well-known three-body resonance. The
second (broad) bump is a composition of overlapping soft modes of
multipolarities whose relative weights depend on
transferred momentum and reaction type. Inelastic scattering is the most
selective tool for studying the soft dipole excitation mode.Comment: Submitted to Phys. Rev. C., 11 figures using eps
Aboveground biomass of mongolian larch (Larix sibiricledeb.) forests in the eurasian region
We used our database of tree biomass with a number of 433 sample trees of Larix from different ecoregions of Eurasia, involving 61 trees from Mongolia for developing an additive model of biomass tree components. Our approach solved the combined problem of additivity and regionality of the model. Our additive model of tree aboveground biomass was harmonized in two ways: first, it eliminated the internal contradictions of the component and of the total biomass equations, secondly, it took into account regional (and correspondingly species-specific) differences of trees in its component structure. A significant excess of larch biomass in the forest-tundra is found that may be explained by permafrost conditions, by tree growth in low-yielding stands with a high basic density of stem wood and relatively high developed tree crown in open stands. The aboveground biomass of larch trees in Mongolia does not stand out against the background of the most ecoregions of Eurasia. Based on our results, we conclude that the growing conditions of larch in Mongolia are not as tough as it was suggested earlier by other scientists. Biomass relations between regions may be explained by unknown and unaccounted factors and errors of measurements in all their phases (assessment of age, diameter, height of a tree, the selection of supposedly representative samples of component biomass, their drying, weighing, etc.). The question what explains the regional differences in the structure of biomass of trees with the same linear dimensions of their stems, remains open. Undoubtedly, the differences in tree age here play an important role. Also, important factor is the variation in the morphological structure of stands, which, in turn, is determined by both climatic and edaphic factors. The obtained models allow the determination of larch forest biomass in different ecoregions of Eurasia with the help of height and diameter data. © 2019, Lomonosov Moscow State University. All rights reserved
Algebraic Model for scattering of three-s-cluster systems. II. Resonances in the three-cluster continuum of 6He and 6Be
The resonance states embedded in the three-cluster continuum of 6He and 6Be
are obtained in the Algebraic Version of the Resonating Group Method. The model
accounts for a correct treatment of the Pauli principle. It also provides the
correct three-cluster continuum boundary conditions by using a Hyperspherical
Harmonics basis. The model reproduces the observed resonances well and achieves
good agreement with other models. A better understanding for the process of
formation and decay of the resonance states in six-nucleon systems is obtained.Comment: 8 pages, 10 postscript figures, submitted to Phys. Rev.
Quantum-enhanced magnetometry by phase estimation algorithms with a single artificial atom
Phase estimation algorithms are key protocols in quantum information processing. Besides applications in quantum computing, they can also be employed in metrology as they allow for fast extraction of information stored in the quantum state of a system. Here, we implement two suitably modified phase estimation procedures, the Kitaev and the semiclassical Fourier-transform algorithms, using an artificial atom realized with a superconducting transmon circuit. We demonstrate that both algorithms yield a flux sensitivity exceeding the classical shot-noise limit of the device, allowing one to approach the Heisenberg limit. Our experiment paves the way for the use of superconducting qubits as metrological devices which are potentially able to outperform the best existing flux sensors with a sensitivity enhanced by few orders of magnitude
Three-body halos. V. Computations of continuum spectra for Borromean nuclei
We solve the coordinate space Faddeev equations in the continuum. We employ
hyperspherical coordinates and provide analytical expressions allowing easy
computation of the effective potentials at distances much larger than the
ranges of the interactions where only s-waves in the different Jacobi
coordinates couple. Realistic computations are carried out for the Borromean
halo nuclei 6He (n+n+\alpha) for J\pi = 0+-, 1+-, 2+- and 11Li (n+n+9Li) for
(1/2)+-, (3/2)+-, (5/2)+-. Ground state properties, strength functions, Coulomb
dissociation cross sections, phase shifts, complex S-matrix poles are computed
and compared to available experimental data. We find enhancements of the
strength functions at low energies and a number of low-lying S-matrix poles.Comment: 35 pages, 14 figure
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