168 research outputs found
Quantum information as a non-Kolmogorovian generalization of Shannon's theory
In this article we discuss the formal structure of a generalized information
theory based on the extension of the probability calculus of Kolmogorov to a
(possibly) non-commutative setting. By studying this framework, we argue that
quantum information can be considered as a particular case of a huge family of
non-commutative extensions of its classical counterpart. In any conceivable
information theory, the possibility of dealing with different kinds of
information measures plays a key role. Here, we generalize a notion of state
spectrum, allowing us to introduce a majorization relation and a new family of
generalized entropic measures
Generalized probabilities in statistical theories
In this review article we present different formal frameworks for the
description of generalized probabilities in statistical theories. We discuss
the particular cases of probabilities appearing in classical and quantum
mechanics, possible generalizations of the approaches of A. N. Kolmogorov and
R. T. Cox to non-commutative models, and the approach to generalized
probabilities based on convex sets
Evolution of quantum observables: from non-commutativity to commutativity
A fundamental aspect of the quantum-to-classical limit is the transition from a non-
commutative algebra of observables to commutative one.However, this transition is not possible if we only consider unitary evolutions. One way to describe this transition is to consider the Gamow vectors, which introduce exponential decays in the evolution. In this paper, we give two mathematical models in which this transition happens in the infinite time limit. In the first one, we consider operators acting on the space of the Gamow vectors, which represent quantum resonances. In the second one, we use an algebraic formalism from scattering theory. We construct a non-commuting algebra which commutes in the infinite time limit.MINECO Grant MTM2014- 57129-C2-1-P. Junta de Castilla y Leon Grants BU229P18, VA137G18
Approximate transformations of bipartite pure-state entanglement from the majorization lattice
We study the problem of deterministic transformations of an \textit{initial}
pure entangled quantum state, , into a \textit{target} pure
entangled quantum state, , by using \textit{local operations and
classical communication} (LOCC). A celebrated result of Nielsen [Phys. Rev.
Lett. \textbf{83}, 436 (1999)] gives the necessary and sufficient condition
that makes this entanglement transformation process possible. Indeed, this
process can be achieved if and only if the majorization relation holds, where and are probability vectors obtained by taking
the squares of the Schmidt coefficients of the initial and target states,
respectively. In general, this condition is not fulfilled. However, one can
look for an \textit{approximate} entanglement transformation. Vidal \textit{et.
al} [Phys. Rev. A \textbf{62}, 012304 (2000)] have proposed a deterministic
transformation using LOCC in order to obtain a target state
most approximate to in terms of
maximal fidelity between them. Here, we show a strategy to deal with
approximate entanglement transformations based on the properties of the
\textit{majorization lattice}. More precisely, we propose as approximate target
state one whose Schmidt coefficients are given by the supremum between
and . Our proposal is inspired on the observation that fidelity does not
respect the majorization relation in general. Remarkably enough, we find that
for some particular interesting cases, like two-qubit pure states or the
entanglement concentration protocol, both proposals are coincident.Comment: Revised manuscript close to the accepted version in Physica A (10
pages, 1 figure
A family of generalized quantum entropies: definition and properties
We present a quantum version of the generalized -entropies,
introduced by Salicr\'u \textit{et al.} for the study of classical probability
distributions. We establish their basic properties, and show that already known
quantum entropies such as von Neumann, and quantum versions of R\'enyi,
Tsallis, and unified entropies, constitute particular classes of the present
general quantum Salicr\'u form. We exhibit that majorization plays a key role
in explaining most of their common features. We give a characterization of the
quantum -entropies under the action of quantum operations, and study
their properties for composite systems. We apply these generalized entropies to
the problem of detection of quantum entanglement, and introduce a discussion on
possible generalized conditional entropies as well.Comment: 26 pages, 1 figure. Close to published versio
Generalizing entanglement via informational invariance for arbitrary statistical theories
Given an arbitrary statistical theory, different from quantum mechanics, how
to decide which are the nonclassical correlations? We present a formal
framework which allows for a definition of nonclassical correlations in such
theories, alternative to the current one. This enables one to formulate
extrapolations of some important quantum mechanical features via adequate
extensions of reciprocal maps relating states of a system with states of its
subsystems. These extended maps permit one to generalize i) separability
measures to any arbitrary statistical model as well as ii) previous
entanglement criteria. The standard definition of entanglement becomes just a
particular case of the ensuing, more general notion.Comment: Improved versio
Indistinguishability right from the start in standard quantum mechanics
We discuss a reconstruction of standard quantum mechanics assuming
indistinguishability right from the start, by appealing to quasi-set theory.
After recalling the fundamental aspects of the construction and introducing
some improvements in the original formulation, we extract some conclusions for
the interpretation of quantum theory
Convex politopes and quantum separability
We advance a novel perspective of the entanglement issue that appeals to the
Schlienz-Mahler measure [Phys. Rev. A 52, 4396 (1995)]. Related to it, we
propose an criterium based on the consideration of convex subsets of quantum
states. This criterium generalizes a property of product states to convex
subsets (of the set of quantum-states) that is able to uncover a new
geometrical property of the separability property
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