767 research outputs found
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
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
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
Analytical E1 strength functions of two-neutron halo nuclei: the 6-He example
An analytical model is developed to study the spectra of electromagnetic
dissociation of two-neutron halo nuclei without precise knowledge about initial
and final states. Phenomenological three-cluster bound state wave functions,
reproducing the most relevant features of these nuclei, are used along with no
interaction final states. The 6-He nucleus is considered as a test case, and a
good agreement with experimental data concerning the shape of the spectrum and
the magnitude of the strength function is found.Comment: 19 pages, 4 figures Accepted for publishing in Nuclear Physics
Quantum sensing with tunable superconducting qubits: optimization and speed-up
Sensing and metrology play an important role in fundamental science and
applications by fulfilling the ever-present need for more precise data sets and
by allowing researchers to make more reliable conclusions on the validity of
theoretical models. Sensors are ubiquitous. They are used in applications
across a diverse range of fields including gravity imaging, geology,
navigation, security, timekeeping, spectroscopy, chemistry, magnetometry,
healthcare, and medicine. Current progress in quantum technologies has
inevitably triggered the exploration of the use of quantum systems as sensors
with new and improved capabilities. This article describes the optimization of
the quantum-enhanced sensing of external magnetic fluxes with a Kitaev phase
estimation algorithm based on a sensor with tunable transmon qubits. It
provides the optimal flux biasing point for sensors with different maximal
qubit transition frequencies. An estimation of decoherence rates is made for a
given design. The use of and qubit entangled states for sensing are
compared in simulation with the single qubit case. The flux sensing accuracy
reaches and scales with time as which proves
the speed-up of sensing with high ultimate accuracy.Comment: 13 pages, 7 figures, 1 table. arXiv admin note: substantial text
overlap with arXiv:2103.1102
Asymptotic representation of a solution to a singular perturbation linear time-optimal problem
A time-optimal control problem is considered for a linear system with fast and slow variables and smooth geometric constraints on the control. An asymptotic expansion of the optimal time up to the second order of smallness is constructed and validated. © 2013 Pleiades Publishing, Ltd
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