4,446 research outputs found
Rank properties of exposed positive maps
Let \cK and \cH be finite dimensional Hilbert spaces and let \fP denote
the cone of all positive linear maps acting from \fB(\cK) into \fB(\cH). We
show that each map of the form or is an
exposed point of \fP. We also show that if a map is an exposed point
of \fP then either is rank 1 non-increasing or \rank\phi(P)>1 for
any one-dimensional projection P\in\fB(\cK).Comment: 6 pages, last section removed - it will be a part of another pape
Monogamy of Bell's inequality violations in non-signaling theories
We derive monogamy relations (tradeoffs) between strengths of violations of
Bell's inequalities from the non-signaling condition. Our result applies to
general Bell inequalities with an arbitrary large number of partners, outcomes
and measurement settings. The method is simple, efficient and does not require
linear programming. The results are used to derive optimal fidelity for
asymmetric cloning in nonsignaling theories.Comment: 4 pages, 2 figures, published versio
Efficient bounds on quantum communication rates via their reduced variants
We investigate one-way communication scenarios where Bob manipulating on his
parts can transfer some sub-system to the environment. We define reduced
versions of quantum communication rates and further, prove new upper bounds on
one-way quantum secret key, distillable entanglement and quantum channel
capacity by means of their reduced versions. It is shown that in some cases
they drastically improve their estimation.Comment: 6 pages, RevTe
-Deformed Statistics and Classical Fourmomentum Addition Law
We consider -deformed relativistic symmetries described algebraically
by modified Majid-Ruegg bicrossproduct basis and investigate the quantization
of field oscillators for the -deformed free scalar fields on
-Minkowski space. By modification of standard multiplication rule, we
postulate the -deformed algebra of bosonic creation and annihilation
operators. Our algebra permits to define the n-particle states with classical
addition law for the fourmomenta in a way which is not in contradiction with
the nonsymmetric quantum fourmomentum coproduct. We introduce -deformed
Fock space generated by our -deformed oscillators which satisfy the
standard algebraic relations with modified -multiplication rule. We
show that such a -deformed bosonic Fock space is endowed with the
conventional bosonic symmetry properties. Finally we discuss the role of
-deformed algebra of oscillators in field-theoretic noncommutative
framework.Comment: LaTeX, 12 pages. V2: second part of chapter 4 changed, new references
and comments added. V3: formula (14) corrected. Some additional explanations
added. V4: further comments about algebraic structure are adde
N-enlarged Galilei Hopf algebra and its twist deformations
The N-enlarged Galilei Hopf algebra is constructed. Its twist deformations
are considered and the corresponding twisted space-times are derived.Comment: 8 pages, no figure
Quantum-mechanical machinery for rational decision-making in classical guessing game
In quantum game theory, one of the most intriguing and important questions
is, "Is it possible to get quantum advantages without any modification of the
classical game?" The answer to this question so far has largely been negative.
So far, it has usually been thought that a change of the classical game setting
appears to be unavoidable for getting the quantum advantages. However, we give
an affirmative answer here, focusing on the decision-making process (we call
'reasoning') to generate the best strategy, which may occur internally, e.g.,
in the player's brain. To show this, we consider a classical guessing game. We
then define a one-player reasoning problem in the context of the
decision-making theory, where the machinery processes are designed to simulate
classical and quantum reasoning. In such settings, we present a scenario where
a rational player is able to make better use of his/her weak preferences due to
quantum reasoning, without any altering or resetting of the classically defined
game. We also argue in further analysis that the quantum reasoning may make the
player fail, and even make the situation worse, due to any inappropriate
preferences.Comment: 9 pages, 10 figures, The scenario is more improve
Matter-wave analog of an optical random laser
The accumulation of atoms in the lowest energy level of a trap and the
subsequent out-coupling of these atoms is a realization of a matter-wave analog
of a conventional optical laser. Optical random lasers require materials that
provide optical gain but, contrary to conventional lasers, the modes are
determined by multiple scattering and not a cavity. We show that a
Bose-Einstein condensate can be loaded in a spatially correlated disorder
potential prepared in such a way that the Anderson localization phenomenon
operates as a band-pass filter. A multiple scattering process selects atoms
with certain momenta and determines laser modes which represents a matter-wave
analog of an optical random laser.Comment: 4 pages, 3 figures version accepted for publication in Phys. Rev. A;
minor changes, the present title substituted for "Atom Random Laser
N-particle nonclassicality without N-particle correlations
Most of known multipartite Bell inequalities involve correlation functions
for all subsystems. They are useless for entangled states without such
correlations. We give a method of derivation of families of Bell inequalities
for N parties, which involve, e.g., only (N-1)-partite correlations, but still
are able to detect proper N-partite entanglement. We present an inequality
which reveals five-partite entanglement despite only four-partite correlations.
Classes of inequalities introduced here can be put into a handy form of a
single non-linear inequality. An example is given of an N qubit state, which
strongly violates such an inequality, despite having no N-qubit correlations.
This surprising property might be of potential value for quantum information
tasks.Comment: 5 page
A simplified implementation of the least squares solution for pairwise comparisons matrices
This is a follow up to "Solution of the least squares method problem of pairwise comparisons matrix" by Bozóki published by this journal in 2008. Familiarity with this paper is essential and assumed. For lower inconsistency and decreased accuracy, our proposed solutions run in seconds instead of days. As such, they may be useful for researchers willing to use the least squares method (LSM) instead of the geometric means (GM) method
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