8,278 research outputs found
Optimal quantum state reconstruction for cold trapped ions
We study the physical implementation of an optimal tomographic reconstruction
scheme for the case of determining the state of a multi-qubit system, where
trapped ions are used for defining qubits. The protocol is based on the use of
mutually unbiased measurements and on the physical information described in H.
H\"{a}ffner \emph{et. al} [Nature \textbf{438}, 643-646 (2005)]. We introduce
the concept of physical complexity for different types of unbiased measurements
and analyze their generation in terms of one and two qubit gates for trapped
ions.Comment: Accepted for publication in Phys. Rev. A as Rap. Com
Single top polarisation as a window to new physics
We discuss the effect of heavy new physics, parameterised in terms of
four-fermion operators, in the polarisation of single top (anti-)quarks in the
-channel process at the LHC. It is found that for operators involving a
right-handed top quark field the relative effect on the longitudinal
polarisation is twice larger than the relative effect on the total cross
section. This enhanced dependence on possible four-fermion contributions makes
the polarisation measurements specially interesting, in particular at high
momenta.Comment: LaTeX 10 pages. v2: comments and references added, journal versio
FCNCs in supersymmetric multi-Higgs doublet models
We conduct a general discussion of supersymmetric models with three families
in the Higgs sector. We analyse the scalar potential, and investigate the
minima conditions, deriving the mass matrices for the scalar, pseudoscalar and
charged states. Depending on the Yukawa couplings and the Higgs spectrum, the
model might allow the occurrence of potentially dangerous flavour changing
neutral currents at the tree-level. We compute model-independent contributions
for several observables, and as an example we apply this general analysis to a
specific model of quark-Higgs interactions, discussing how compatibility with
current experimental data constrains the Higgs sector.Comment: 30 pages, 9 figures. Comments and references added. Final version
published in Physical Review
Ground state of medium-heavy doubly-closed shell nuclei in correlated basis function theory
The correlated basis function theory is applied to the study of medium-heavy
doubly closed shell nuclei with different wave functions for protons and
neutrons and in the jj coupling scheme. State dependent correlations including
tensor correlations are used. Realistic two-body interactions of Argonne and
Urbana type, together with three-body interactions have been used to calculate
ground state energies and density distributions of the 12C, 16O, 40Ca, 48Ca and
208Pb nuclei.Comment: Latex 10 pages, 3 Tables, 10 Figure
Renormalized Fermi hypernetted chain approach in medium-heavy nuclei
The application of the Correlated basis function theory and of the Fermi
hypernetted chain technique, to the description of the ground state of
medium-heavy nuclei is reviewed. We discuss how the formalism, originally
developed for symmetric nuclear matter, should be changed in order to describe
finite nuclear systems, with different number of protons and neutrons. This
approach allows us to describe doubly closed shell nuclei by using microscopic
nucleon-nucleon interactions. We presents results of numerical calculations
done with two-nucleon interactions of Argonne type,implemented with three-body
forces of Urbana type. Our results regard ground-state energies, matter, charge
and momentum distributions, natural orbits, occupation numbers, quasi-hole wave
functions and spectroscopic factors of 12C, 16O, 40Ca, 48Ca and 208Pb nuclei.Comment: 127 Pages, 37 figures, Accepted for publication in Physics Report
Experimental scheme for unambiguous discrimination of linearly independent symmetric states
We propose an optimal discrimination scheme for a case of four linearly
independent nonorthogonal symmetric quantum states, based on linear optics
only. The probability of discrimination is in agreement with the optimal
probability for unambiguous discrimination among N symmetric states [Phys.
Lett. A \textbf{250}, 223 (1998)]. The experimental setup can be extended for
the case of discrimination among nonorthogonal symmetric quantum states
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