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## Electrostatic potentials and polarization effects in proton-molecule interactions by means of multipoles from the quantum theory of atoms in molecules

Fonte: WILEY-BLACKWELL; HOBOKEN
Publicador: WILEY-BLACKWELL; HOBOKEN

Tipo: Artigo de Revista Científica

ENG

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#QUANTUM THEORY OF ATOMS IN MOLECULES#CHELPG#POLARIZATION#ELECTROSTATIC POTENTIALS#ZERO-FLUX SURFACES#NUMERICAL-INTEGRATION#TOPOLOGICAL ATOMS#ENERGIES#CONVERGENCE#DENSITY#MOMENTS

Some atomic multipoles (charges, dipoles and quadrupoles) from the Quantum Theory of Atoms in Molecules (QTAIM) and CHELPG charges are used to investigate interactions between a proton and a molecule (F2, Cl2, BF, AlF, BeO, MgO, LiH, H2CO, NH3, PH3, BF3, and CO2). Calculations were done at the B3LYP/6-311G(3d,3p) level. The main aspect of this work is the investigation of polarization effects over electrostatic potentials and atomic multipoles along a medium to long range of interaction distances. Large electronic charge fluxes and polarization changes are induced by a proton mainly when this positive particle approaches the least electronegative atom of diatomic heteronuclear molecules. The search for simple equations to describe polarization on electrostatic potentials from QTAIM quantities resulted in linear relations with r-4 (r is the interaction distance) for many cases. Moreover, the contribution from atomic dipoles to these potentials is usually the most affected contribution by polarization what reinforces the need for these dipoles to a minimal description of purely electrostatic interactions. Finally, CHELPG charges provide a description of polarization effects on electrostatic potentials that is in disagreement with physical arguments for certain of these molecules. (c) 2012 Wiley Periodicals...

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## On the individuation of physical systems in quantum theory.

Fonte: Universidade de Adelaide
Publicador: Universidade de Adelaide

Tipo: Tese de Doutorado

Publicado em //2014

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What theoretical structures characterise our notions of what it means for a whole physical system to be the sum of its parts? We explore various aspects of this question, with emphasise on quantum theory, from the following perspective: A physical theory constitutes the definition of a set of propositions with logical relationships between them such that probabilities can be used to judge the merits of the theory, given empirical evidence. The logical relationships between the propositions characterise our semantic notions such as individuation. We distinguish between the ontological and epistemological notions of individuation. We introduce the notion of ontological individuation within the context of ontological models. A subsystem is defined as a proposition that provides necessary and sufficient information for making useful predictions. This definition to some extent generalises the notions of separability and local causality to define systems that may not be local. It highlights the unified motivations for many assumptions in the literature, such as measurement independence, and points to hidden assumptions of causality and mutual exclusivity that occur when defining systems. An epistemic no-signalling criterion gives rise to a tensor product structure for epistemic systems in quantum theory. We utilise a symmetry emergent from this structure to derive a bound on the observability of a large class of operations...

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## The black hole information problem beyond quantum theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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#High Energy Physics - Theory#General Relativity and Quantum Cosmology#Mathematical Physics#Quantum Physics

The origin of black hole entropy and the black hole information problem
provide important clues for trying to piece together a quantum theory of
gravity. Thus far, discussions on this topic have mostly assumed that in a
consistent theory of gravity and quantum mechanics, quantum theory will be
unmodified. Here, we examine the black hole information problem in the context
of generalisations of quantum theory. In particular, we examine black holes in
the setting of generalised probabilistic theories, in which quantum theory and
classical probability theory are special cases. We compute the time it takes
information to escape a black hole, assuming that information is preserved. We
find that under some very general assumptions, the arguments of Page (that
information should escape the black hole after half the Hawking photons have
been emitted), and the black-hole mirror result of Hayden and Preskill (that
information can escape quickly) need to be modified. The modification is
determined entirely by what we call the Wootters-Hardy parameter associated
with a theory. We find that although the information leaves the black hole
after enough photons have been emitted, it is fairly generic that it fails to
appear outside the black hole at this point -- something impossible in quantum
theory due to the no-hiding theorem. The information is neither inside the
black hole...

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## Quantum Theory as emergent from an undulatory translocal Sub-Quantum Level

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 08/05/2012

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We argue that quantum theory is a low-energy effective theory which emerges
from some sub-quantum level theory which is of an undulatory and translocal
character. We show the close connection of quantum theory with both gravity and
the holographic principle which are different phenomena of one and the same
theory on this primordial level. An important role in our analysis is played by
the concept of a generalized renormalization group connecting this primordial
level and e.g. quantum theory plus a continuous space-time. We show that
characteristic phenomena like the seemingly instantaneous state reduction, the
EPR-paradox or the problem of polydimensions can be understood in our
undulatory translocal theory in a realistic way. Most importantly, we give a
realistic interpretation of the phasefunction as a collective action variable
in the spirit of Bohm and explain the emergence of a macroscopic notion of
time.; Comment: 32 pages, Latex

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## Some Reflections on the Status of Conventional Quantum Theory when Applied to Quantum Gravity

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 13/06/2002

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All current approaches to quantum gravity employ essentially standard quantum
theory including, in particular, continuum quantities such as the real or
complex numbers. However, I wish to argue that this may be fundamentally wrong
in so far as the use of these continuum quantities in standard quantum theory
can be traced back to certain {\em a priori} assumptions about the nature of
space and time: assumptions that may be incompatible with the view of space and
time adopted by a quantum gravity theory. My conjecture is that in, some yet to
be determined sense, to each type of space-time there is associated a
corresponding type of quantum theory in which continuum quantities do not
necessarily appear, being replaced with structures that are appropriate to the
specific space-time.
Topos theory then arises as a possible tool for `gluing' together these
different theories associated with the different space-times. As a concrete
example of the use of topos ideas, I summarise recent work applying presheaf
theory to the Kochen-Specher theorem and the assignment of values to physical
quantities in a quantum theory.; Comment: Latex2e

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## Higher-order interference in extensions of quantum theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 13/10/2015

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Quantum interference lies at the heart of several quantum computational
speed-ups and provides a striking example of a phenomenon with no classical
counterpart. An intriguing feature of quantum interference arises in a three
slit experiment. In this set-up, the interference pattern can be written in
terms of the two and one slit patterns obtained by blocking some of the slits.
This is in stark contrast with the standard two slit experiment, where the
interference pattern is irreducible. This was first noted by Rafael Sorkin, who
asked why quantum theory only exhibits irreducible interference in the two slit
experiment. One approach to this problem is to compare the predictions of
quantum theory to those of operationally-defined `foil' theories, in the hope
of determining whether theories exhibiting higher-order interference suffer
from pathological -- or at least undesirable -- features. In this paper two
proposed extensions of quantum theory are considered: the theory of Density
Cubes proposed by Dakic, Paterek and Brukner, which has been shown to exhibit
irreducible interference in the three slit set-up, and the Quartic Quantum
Theory of Zyczkowski. The theory of Density Cubes will be shown to provide an
advantage over quantum theory in a certain computational task and to posses a
well-defined mechanism which leads to the emergence of quantum theory --
analogous to the emergence of classical physics from quantum theory via
decoherence. Despite this...

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## Causal Quantum Theory and the Collapse Locality Loophole

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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Causal quantum theory is an umbrella term for ordinary quantum theory
modified by two hypotheses: state vector reduction is a well-defined process,
and strict local causality applies. The first of these holds in some versions
of Copenhagen quantum theory and need not necessarily imply practically
testable deviations from ordinary quantum theory. The second implies that
measurement events which are spacelike separated have no non-local
correlations. To test this prediction, which sharply differs from standard
quantum theory, requires a precise theory of state vector reduction.
Formally speaking, any precise version of causal quantum theory defines a
local hidden variable theory. However, causal quantum theory is most naturally
seen as a variant of standard quantum theory. For that reason it seems a more
serious rival to standard quantum theory than local hidden variable models
relying on the locality or detector efficiency loopholes.
Some plausible versions of causal quantum theory are not refuted by any Bell
experiments to date, nor is it obvious that they are inconsistent with other
experiments. They evade refutation via a neglected loophole in Bell experiments
-- the {\it collapse locality loophole} -- which exists because of the possible
time lag between a particle entering a measuring device and a collapse taking
place. Fairly definitive tests of causal versus standard quantum theory could
be made by observing entangled particles separated by $\approx 0.1$ light
seconds.; Comment: Discussion expanded; typos corrected; references added

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## A Realistic Deterministic Quantum Theory Using Borelian-Normal Numbers

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 10/05/2002

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The elements of a deterministic quantum theory are developed, which
reformulates and extends standard quantum theory. The proposed theory is
`realistic' in the sense that in it, a general M-level quantum state is
represented by a single real number r. Surprising as it may seem, this real
number is shown to contain the same probabilistic information as the standard
Hilbert-space state, plus additional information from which measurement outcome
is determined. A crucial concept in achieving this is that of Borelian
(number-theoretic) normality. The essential role of complex numbers in standard
quantum theory is subsumed by the action of a set of self-similar permutation
operators on the digits and places of the base-M expansion of a base-M
Borelian-normal r; these permutation operators are shown to have complex
structure and leave invariant the normality of the underlying real number. The
set of real numbers generated by these permutations defines not only the
Hilbert space of standard quantum theory, but also, in addition, the sample
space from which quantum measurement outcomes can be objectively determined.
Dynamical real-number state reduction is precisely described by deterministic
number-theoretic operators that reduce the degree of normality of r; from the
degree of normality one can infer the standard quantum-theoretic trace rule for
measurement probability. All the foundational difficulties of standard quantum
theory are described in terms of the proposed theory. It is shown that the
real-number states of the proposed theory are precisely its beables.; Comment: 38 pages...

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## The trouble with orbits: the Stark effect in the old and the new quantum theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 21/04/2014

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The old quantum theory and Schr\"odinger's wave mechanics (and other forms of
quantum mechanics) give the same results for the line splittings in the
first-order Stark effect in hydrogen, the leading terms in the splitting of the
spectral lines emitted by a hydrogen atom in an external electric field. We
examine the account of the effect in the old quantum theory, which was hailed
as a major success of that theory, from the point of view of wave mechanics.
First, we show how the new quantum mechanics solves a fundamental problem one
runs into in the old quantum theory with the Stark effect. It turns out that,
even without an external field, it depends on the coordinates in which the
quantum conditions are imposed which electron orbits are allowed in a hydrogen
atom. The allowed energy levels and hence the line splittings are independent
of the coordinates used but the size and eccentricity of the orbits are not. In
the new quantum theory, this worrisome non-uniqueness of orbits turns into the
perfectly innocuous non-uniqueness of bases in Hilbert space. Second, we review
how the so-called WKB (Wentzel-Kramers-Brillouin) approximation method for
solving the Schr\"odinger equation reproduces the quantum conditions of the old
quantum theory amended by some additional half-integer terms. These extra terms
remove the need for some arbitrary extra restrictions on the allowed orbits
that the old quantum theory required over and above the basic quantum
conditions

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## Generalized Galilean Transformations and the Measurement Problem in the Entropic Dynamics Approach to Quantum Theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/05/2011

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Quantum mechanics is an extremely successful and accurate physical theory,
yet since its inception, it has been afflicted with numerous conceptual
difficulties. The primary subject of this thesis is the theory of entropic
quantum dynamics (EQD), which seeks to avoid these conceptual problems by
interpreting quantum theory from an informational perspective.
We begin by reviewing probability theory as a means of rationally quantifying
uncertainties. We then discuss how probabilities can be updated with the method
of maximum entropy (ME). We then review some motivating difficulties in quantum
mechanics before discussing Caticha's work in deriving quantum theory from the
approach of entropic dynamics.
After entropic dynamics is introduced, we develop the concepts of symmetries
and transformations from an informational perspective. The primary result is
the formulation of a symmetry condition that any transformation must satisfy in
order to qualify as a symmetry in EQD. We then proceed to apply this condition
to the extended Galilean transformation. This transformation is of interest as
it exhibits features of both special and general relativity. The transformation
yields a gravitational potential that arises from an equivalence of
information.
We conclude the thesis with a discussion of the measurement problem in
quantum mechanics. We discuss the difficulties that arise in the standard
quantum mechanical approach to measurement before developing our theory of
entropic measurement. In entropic dynamics...

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## Topos Quantum Theory Reduced by Context-Selection Functors

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/07/2015

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In this paper, we deal with quantum theories on presheaves and sheaves on
context categories consisting of commutative von Neumann algebras of bounded
operators on a Hilbert space, from two viewpoints. One is to reduce
presheaf-based topos quantum theory via sheafification, and the other is to
import quantum probabilities to the reduced sheaf quantum theory. The first is
done by means of a functor that selects some expedient contexts. It defines a
Grothendieck topology on the category consisting of all contexts, hence,
induces a sheaf topos on which we construct a downsized quantum theory. Also,
we show that the sheaf quantum theory can be replaced by an equivalent, more
manageable presheaf quantum theory. Quantum probabilities are imported by means
of a Grothendieck topology that is defined on a category consisting of
probabilities and enables to regard them as intuitionistic truth-values. From
these topologies, we construct another Grothendieck topology that is defined on
the product of the context category and the probability category and reflects
the selection of contexts and the identification of probabilities with
truth-values. We construct a quantum theory equipped with quantum probabilities
as truth-values on the sheaf topos induced by the Grothendieck topology.; Comment: 38pages

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## Quantum theory and the role of mind in nature

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/03/2001

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Orthodox Copenhagen quantum theory renounces the quest to understand the
reality in which we are imbedded, and settles for practical rules describing
connections between our observations. Many physicist have regarded this
renunciation of our effort to describe nature herself as premature, and John
von Neumann reformulated quantum theory as a theory of an evolving objective
universe interacting with human consciousness. This interaction is associated
both in Copenhagen quantum theory and in von Neumann quantum theory with a
sudden change that brings the objective physical state of a system in line with
a subjectively felt psychical reality. The objective physical state is thereby
converted from a material substrate to an informational and dispositional
substrate that carries both the information incorporated into it by the
psychical realities, and certain dispositions for the occurrence of future
psychical realities. The present work examines and proposes solutions to two
problems that have appeared to block the development of this conception of
nature. The first problem is how to reconcile this theory with the principles
of relativistic quantum field theory; the second problem is to understand
whether, strictly within quantum theory...

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## Quantum theory without Hilbert spaces

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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Quantum theory does not only predict probabilities, but also relative phases
for any experiment, that involves measurements of an ensemble of systems at
different moments of time. We argue, that any operational formulation of
quantum theory needs an algebra of observables and an object that incorporates
the information about relative phases and probabilities. The latter is the
(de)coherence functional, introduced by the consistent histories approach to
quantum theory. The acceptance of relative phases as a primitive ingredient of
any quantum theory, liberates us from the need to use a Hilbert space and
non-commutative observables. It is shown, that quantum phenomena are adequately
described by a theory of relative phases and non-additive probabilities on the
classical phase space. The only difference lies on the type of observables that
correspond to sharp measurements. This class of theories does not suffer from
the consequences of Bell's theorem (it is not a theory of Kolmogorov
probabilities) and Kochen- Specker's theorem (it has distributive "logic"). We
discuss its predictability properties, the meaning of the classical limit and
attempt to see if it can be experimentally distinguished from standard quantum
theory. Our construction is operational and statistical...

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## Toy Model for a Relational Formulation of Quantum Theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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In the absence of an external frame of reference physical degrees of freedom
must describe relations between systems. Using a simple model, we investigate
how such a relational quantum theory naturally arises by promoting reference
systems to the status of dynamical entities. Our goal is to demonstrate using
elementary quantum theory how any quantum mechanical experiment admits a purely
relational description at a fundamental level, from which the original
"non-relational" theory emerges in a semi-classical limit. According to this
thesis, the non-relational theory is therefore an approximation of the
fundamental relational theory. We propose four simple rules that can be used to
translate an "orthodox" quantum mechanical description into a relational
description, independent of an external spacial reference frame or clock. The
techniques used to construct these relational theories are motivated by a
Bayesian approach to quantum mechanics, and rely on the noiseless subsystem
method of quantum information science used to protect quantum states against
undesired noise. The relational theory naturally predicts a fundamental
decoherence mechanism, so an arrow of time emerges from a time-symmetric
theory. Moreover, there is no need for a "collapse of the wave packet" in our
model: the probability interpretation is only applied to diagonal density
operators. Finally...

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## The de Broglie-Bohm pilot-wave interpretation of quantum theory

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/06/2005

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In this thesis we study the de Broglie-Bohm pilot-wave interpretation of
quantum theory. We consider the domain of non-relativistic quantum theory,
relativistic quantum theory and quantum field theory, and in each domain we
consider the possibility of formulating a pilot-wave interpretation. For
non-relativistic quantum theory a pilot-wave interpretation in terms of
particle beables can readily be formulated. But this interpretation can in
general not straightforwardly be generalized to relativistic wave equations.
The problems which prevent us from devising a pilot-wave interpretation for
relativistic wave equations also plague the standard quantum mechanical
interpretation, where these problems led to the conception of quantum field
theory. Therefore most of our attention is focussed on the construction of a
pilot-wave interpretation for quantum field theory. We thereby favour the field
beable approach, developed amongst others by Bohm, Hiley, Holland, Kaloyerou
and Valentini. Although the field beable approach can be successfully applied
to bosonic quantum field theory, it seems not straightforward to do so for
fermionic quantum field theory.; Comment: Ph.D. thesis, Ghent University, October 2004, 171 pages, 3 figures,
LaTex (revised...

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## Formalism Locality in Quantum Theory and Quantum Gravity

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 31/03/2008

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We expect a theory of Quantum Gravity to be both probabilistic and have
indefinite causal structure. Indefinite causal structure poses particular
problems for theory formulation since many of the core ideas used in the usual
approaches to theory construction depend on having definite causal structure.
For example, the notion of a state across space evolving in time requires that
we have some definite causal structure so we can define a state on a space-like
hypersurface. We will see that many of these problems are mitigated if we are
able to formulate the theory in a "formalism local" (or F-local) fashion. A
formulation of a physical theory is said to be F-local if, in making
predictions for any given arbitrary space-time region, we need only refer to
mathematical objects pertaining to that region. This is a desirable property
both on the grounds of efficiency and since, if we have indefinite causal
structure, it is not clear how to select some other space-time region on which
our calculations may depend. The usual ways of formulating physical theories
(the time evolving state picture, the histories approach, and the local
equations approach) are not F-local.
We set up a framework for probabilistic theories with indefinite causal
structure. This...

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## Toward a Quantum theory of Gravity and a Resolution of the Time paradox

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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One of the major issues confronting theoretical physics is finding a quantum
theory of gravity and a resolution to the cosmological constant problem. It is
believed that a true quantum theory of gravity will lead to a solution to the
this problem. Finding a quantum theory of gravity has been a difficult issue
mainly because of the high energy scale required for testing quantum gravity
which is far the reach of current accelerators. Also general relativity does
not possess a natural time variable thus the nature of time is not clear in
quantum gravity, a problem called the time paradox. The two main approaches are
string theory and loop quantum gravity. String theory unifies all interaction
but provides a perturbative background dependent formulation which violates
general covariance. Loop quantum gravity provides a non-perturbative approach
but does not provide a unified theory of interactions, which most physicist
believe should be the case at Planck scale energies. It doesn't also seem to
connect with low energy phenomena.
In this note I look at how quantum cosmology provides useful inference toward
a quantum gravity theory by merging inputs from the perturbative and the
non-perturbative approaches, and resolving the time paradox issue.; Comment: 6 pages no figure. Minor corrections

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## Interpretations of quantum theory: A map of madness

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 15/09/2015

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Motivated by some recent news, a journalist asks a group of physicists:
"What's the meaning of the violation of Bell's inequality?" One physicist
answers: "It means that non-locality is an established fact". Another says:
"There is no non-locality; the message is that measurement outcomes are
irreducibly random". A third one says: "It cannot be answered simply on purely
physical grounds, the answer requires an act of metaphysical judgement".
Puzzled by the answers, the journalist keeps asking questions about quantum
theory: "What is teleported in quantum teleportation?" "How does a quantum
computer really work?" Shockingly, for each of these questions, the journalist
obtains a variety of answers which, in many cases, are mutually exclusive. At
the end of the day, the journalist asks: "How do you plan to make progress if,
after 90 years of quantum theory, you still don't know what it means? How can
you possibly identify the physical principles of quantum theory or expand
quantum theory into gravity if you don't agree on what quantum theory is
about?" Here we argue that it is becoming urgent to solve this too long lasting
problem. For that, we point out that the interpretations of quantum theory are,
essentially, of two types and that these two types are so radically different
that there must be experiments that...

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## Quantum Theory and Beyond: Is Entanglement Special?

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 03/11/2009

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Quantum theory makes the most accurate empirical predictions and yet it lacks
simple, comprehensible physical principles from which the theory can be
uniquely derived. A broad class of probabilistic theories exist which all share
some features with quantum theory, such as probabilistic predictions for
individual outcomes (indeterminism), the impossibility of information transfer
faster than speed of light (no-signaling) or the impossibility of copying of
unknown states (no-cloning). A vast majority of attempts to find physical
principles behind quantum theory either fall short of deriving the theory
uniquely from the principles or are based on abstract mathematical assumptions
that require themselves a more conclusive physical motivation. Here, we show
that classical probability theory and quantum theory can be reconstructed from
three reasonable axioms: (1) (Information capacity) All systems with
information carrying capacity of one bit are equivalent. (2) (Locality) The
state of a composite system is completely determined by measurements on its
subsystems. (3) (Reversibility) Between any two pure states there exists a
reversible transformation. If one requires the transformation from the last
axiom to be continuous, one separates quantum theory from the classical
probabilistic one. A remarkable result following from our reconstruction is
that no probability theory other than quantum theory can exhibit entanglement
without contradicting one or more axioms.; Comment: 14 pages...

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## Quantum theory from the perspective of general probabilistic theories

Fonte: University of Cambridge; Department of Applied Mathematics and Theoretical Physics
Publicador: University of Cambridge; Department of Applied Mathematics and Theoretical Physics

Tipo: Thesis; doctoral; PhD

EN

Relevância na Pesquisa

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#Quantum theory#quantum foundations#non-locality#quantum non-locality#information causality#general probabilistic theories

This thesis explores various perspectives on quantum phenomena, and how our understanding of these phenomena is informed by the study of general probabilistic theories. Particular attention is given to quantum nonlocality, and its interaction with areas of physical and mathematical interest such as entropy, reversible dynamics, information-based games and the idea of negative probability. We begin with a review of non-signaling distributions and convex operational theories, including ?black box? descriptions of experiments and the mathematics of convex vector spaces.
In Chapter 3 we derive various classical and quantum-like quasiprobabilistic representations of arbitrary non-signaling distributions. Previously, results in which the density operator is allowed to become non-positive [1] have proved useful in derivations of quantum theory from physical requirements [2]; we derive a dual result in which the measurement operators instead are allowed to become non-positive, and show that the generation of any non-signaling distribution is possible using a fixed separable state with negligible correlation. We also derive two distinct ?quasi-local? models of non-signaling correlations.
Chapter 4 investigates non-local games, in particular the game known as Information Causality. By analysing the probability of success in this game...

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