656 research outputs found
Remote preparation of arbitrary ensembles and quantum bit commitment
The Hughston-Jozsa-Wootters theorem shows that any finite ensemble of quantum
states can be prepared "at a distance", and it has been used to demonstrate the
insecurity of all bit commitment protocols based on finite quantum systems
without superselection rules. In this paper, we prove a generalized HJW theorem
for arbitrary ensembles of states on a C*-algebra. We then use this result to
demonstrate the insecurity of bit commitment protocols based on infinite
quantum systems, and quantum systems with Abelian superselection rules.Comment: 21 pages, LaTeX. Version 2: Proofs expanded and made more
self-contained; added an example of a bit commitment protocol with continuous
ensemble
Is the decoherence of a system the result of its interaction with the environment?
According to a usual reading, decoherence is a process resulting from the
interaction between a small system and its large environment where information
and energy are dissipated. The particular models treated in the literature on
the subject reinforce this idea since, in general, the behavior of a particle
immersed in a large "bath" composed by many particles is studied. The aim of
this letter is to warn against this usual simplified reading. By means of the
analysis of a well-known model, we will show that decoherence may occur in a
system interacting with an environment consisting of only one particle.Comment: 4 Pages, 5 Figure
Topos-Theoretic Extension of a Modal Interpretation of Quantum Mechanics
This paper deals with topos-theoretic truth-value valuations of quantum
propositions. Concretely, a mathematical framework of a specific type of modal
approach is extended to the topos theory, and further, structures of the
obtained truth-value valuations are investigated. What is taken up is the modal
approach based on a determinate lattice \Dcal(e,R), which is a sublattice of
the lattice \Lcal of all quantum propositions and is determined by a quantum
state and a preferred determinate observable . Topos-theoretic extension
is made in the functor category \Sets^{\CcalR} of which base category
\CcalR is determined by . Each true atom, which determines truth values,
true or false, of all propositions in \Dcal(e,R), generates also a
multi-valued valuation function of which domain and range are \Lcal and a
Heyting algebra given by the subobject classifier in \Sets^{\CcalR},
respectively. All true propositions in \Dcal(e,R) are assigned the top
element of the Heyting algebra by the valuation function. False propositions
including the null proposition are, however, assigned values larger than the
bottom element. This defect can be removed by use of a subobject
semi-classifier. Furthermore, in order to treat all possible determinate
observables in a unified framework, another valuations are constructed in the
functor category \Sets^{\Ccal}. Here, the base category \Ccal includes all
\CcalR's as subcategories. Although \Sets^{\Ccal} has a structure
apparently different from \Sets^{\CcalR}, a subobject semi-classifier of
\Sets^{\Ccal} gives valuations completely equivalent to those in
\Sets^{\CcalR}'s.Comment: LaTeX2
The role of guilt in Posttraumatic Stress Disorder
Background: A growing body of evidence supports the notion that the emotional profile of Posttraumatic Stress Disorder (PTSD) may be more diverse than traditional accounts presume. PTSDâs image as an anxiety-based disorder is undergoing change as the significance of other emotions in its development becomes more evident. Experimental research is needed in order to expand the understanding of underlying processes driving the development of PTSD. Objective: Experimentally test the influence of stressor-related guilt on the occurrence of PTSD symptomatology. Method: A non-clinical student sample faced an analogue trauma, a stressor in the form of a computer crash and related loss of data. We either personally blamed participants for causing the incident (blame group) or told them that it was a technical failure and therefore not their fault (no-blame group). Levels of guilt before and after the incident as well as number and associated distress of incident-related intrusions were assessed using a one-day diary and compared between groups. Results: The guilt manipulation was successful: feelings of guilt significantly increased in the blame group but not in the no-blame group. Furthermore, the blame group showed a significantly higher number of intrusions and associated distress compared to the no-blame group at one-day follow-up. Conclusions: These laboratory findings indicate that feelings of guilt may lead to increased PTSD symptomatology, supporting the view that guilt experienced in reaction to a traumatic event may be part of a causal mechanism driving the development of PTSD
Explaining the unobserved: why quantum mechanics is not only about information
A remarkable theorem by Clifton, Bub and Halvorson (2003)(CBH) characterizes
quantum theory in terms of information--theoretic principles. According to Bub
(2004, 2005) the philosophical significance of the theorem is that quantum
theory should be regarded as a ``principle'' theory about (quantum) information
rather than a ``constructive'' theory about the dynamics of quantum systems.
Here we criticize Bub's principle approach arguing that if the mathematical
formalism of quantum mechanics remains intact then there is no escape route
from solving the measurement problem by constructive theories. We further
propose a (Wigner--type) thought experiment that we argue demonstrates that
quantum mechanics on the information--theoretic approach is incomplete.Comment: 34 Page
The non-relativistic limit of (central-extended) Poincare group and some consequences for quantum actualization
The nonrelativistic limit of the centrally extended Poincar\'e group is
considered and their consequences in the modal Hamiltonian interpretation of
quantum mechanics are discussed [ O. Lombardi and M. Castagnino, Stud. Hist.
Philos. Mod. Phys 39, 380 (2008) ; J. Phys, Conf. Ser. 128, 012014 (2008) ].
Through the assumption that in quantum field theory the Casimir operators of
the Poincar\'e group actualize, the nonrelativistic limit of the latter group
yields to the actualization of the Casimir operators of the Galilei group,
which is in agreement with the actualization rule of previous versions of modal
Hamiltonian interpretation [ Ardenghi et al., Found. Phys. (submitted)
An obstruction based approach to the Kochen-Specker theorem
In [1] it was shown that the Kochen Specker theorem can be written in terms
of the non-existence of global elements of a certain varying set over the
partially ordered set of boolean subalgebras of projection operators on some
Hilbert space. In this paper, we show how obstructions to the construction of
such global elements arise, and how this provides a new way of looking at
proofs of the theorem.Comment: 14 pages, 6 figure
Quantum mechanics is about quantum information
I argue that quantum mechanics is fundamentally a theory about the
representation and manipulation of information, not a theory about the
mechanics of nonclassical waves or particles. The notion of quantum information
is to be understood as a new physical primitive -- just as, following
Einstein's special theory of relativity, a field is no longer regarded as the
physical manifestation of vibrations in a mechanical medium, but recognized as
a new physical primitive in its own right.Comment: 17 pages, forthcoming in Foundations of Physics Festschrift issue for
James Cushing. Revised version: some paragraphs have been added to the final
section clarifying the argument, and various minor clarifying remarks have
been added throughout the tex
Von Neumann's 'No Hidden Variables' Proof: A Re-Appraisal
Since the analysis by John Bell in 1965, the consensus in the literature is
that von Neumann's 'no hidden variables' proof fails to exclude any significant
class of hidden variables. Bell raised the question whether it could be shown
that any hidden variable theory would have to be nonlocal, and in this sense
'like Bohm's theory.' His seminal result provides a positive answer to the
question. I argue that Bell's analysis misconstrues von Neumann's argument.
What von Neumann proved was the impossibility of recovering the quantum
probabilities from a hidden variable theory of dispersion free (deterministic)
states in which the quantum observables are represented as the 'beables' of the
theory, to use Bell's term. That is, the quantum probabilities could not
reflect the distribution of pre-measurement values of beables, but would have
to be derived in some other way, e.g., as in Bohm's theory, where the
probabilities are an artefact of a dynamical process that is not in fact a
measurement of any beable of the system.Comment: 8 pages, no figures; for Peter Mittelstaedt Festschrift issue of
Foundations of Physic
Geometry of quantum correlations
Consider the set Q of quantum correlation vectors for two observers, each
with two possible binary measurements. Quadric (hyperbolic) inequalities which
are satisfied by every vector in Q are proved, and equality holds on a two
dimensional manifold consisting of the local boxes, and all the quantum
correlation vectors that maximally violate the Clauser, Horne, Shimony, and
Holt (CHSH) inequality. The quadric inequalities are tightly related to CHSH,
they are their iterated versions (equation 20). Consequently, it is proved that
Q is contained in a hyperbolic cube whose axes lie along the non-local
(Popescu, Rohrlich) boxes. As an application, a tight constraint on the rate of
local boxes that must be present in every quantum correlation is derived. The
inequalities allow testing the validity of quantum mechanics on the basis of
data available from experiments which test the violation of CHSH. It is noted
how these results can be generalized to the case of n sites, each with two
possible binary measurements.Comment: Published version, slight change in titl
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