295 research outputs found
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 impact of confirmed coronavirus disease 2019 (COVID-19) infection on ambulatory procedures and associated delays in care for asymptomatic patients
© 2021 Elsevier Inc. Background: Since the reopening of ambulatory centers, minimal data has been reported regarding positive tests among patients undergoing ambulatory procedures, associated delays in care, and outcomes of patients previously positive for coronavirus disease 2019. Methods: A retrospective observational case series of ambulatory procedures was performed. Records since the reopening of ambulatory centers in New York were searched for patients with positive coronavirus disease 2019 nasal swab results who underwent ambulatory procedures. Chart reviews were conducted to determine coronavirus disease history and hospitalizations, demographic information, procedure details, and 30-day admissions. Results: A total of 3,762 patients underwent ambulatory procedures. Of those, 53 were previously diagnosed with coronavirus disease 2019 but recovered and tested negative at preprocedural testing. Of the 3,709 asymptomatic patients, 37 (1.00%) tested positive during preprocedural testing; 21 patients had their procedures delayed on average 28.6 days until testing negative, while 16 had their procedures performed before testing negative owing to the time sensitivity of the procedure. There were no major complications or 30-day admissions in any of these asymptomatic patients. Three patients tested positive for coronavirus disease after having an ambulatory procedure. Conclusion: Positive tests in asymptomatic patients led to procedure delays of 28.6 days. No patients who underwent ambulatory procedures after a positive coronavirus disease 2019 test had any coronavirus disease-related complications, regardless of whether or not the procedure was delayed until testing negative. Three patients tested positive for coronavirus disease 2019 after having an ambulatory procedure; however, at an average of 19.7 days after, these cases were likely community acquired making the rate of nosocomial infection negligible
Real-time optical manipulation of cardiac conduction in intact hearts
Optogenetics has provided new insights in cardiovascular research, leading to new methods for cardiac pacing, resynchronization therapy and cardioversion. Although these interventions have clearly demonstrated the feasibility of cardiac manipulation, current optical stimulation strategies do not take into account cardiac wave dynamics in real time. Here, we developed an allâoptical platform complemented by integrated, newly developed software to monitor and control electrical activity in intact mouse hearts. The system combined a wideâfield mesoscope with a digital projector for optogenetic activation. Cardiac functionality could be manipulated either in freeârun mode with submillisecond temporal resolution or in a closedâloop fashion: a tailored hardware and software platform allowed realâtime intervention capable of reacting within 2 ms. The methodology was applied to restore normal electrical activity after atrioventricular block, by triggering the ventricle in response to optically mapped atrial activity with appropriate timing. Realâtime intraventricular manipulation of the propagating electrical wavefront was also demonstrated, opening the prospect for realâtime resynchronization therapy and cardiac defibrillation. Furthermore, the closedâloop approach was applied to simulate a reâentrant circuit across the ventricle demonstrating the capability of our system to manipulate heart conduction with high versatility even in arrhythmogenic conditions. The development of this innovative optical methodology provides the first proofâofâconcept that a realâtime optically based stimulation can control cardiac rhythm in normal and abnormal conditions, promising a new approach for the investigation of the (patho)physiology of the heart
Effects and Propositions
The quantum logical and quantum information-theoretic traditions have exerted
an especially powerful influence on Bub's thinking about the conceptual
foundations of quantum mechanics. This paper discusses both the quantum logical
and information-theoretic traditions from the point of view of their
representational frameworks. I argue that it is at this level, at the level of
its framework, that the quantum logical tradition has retained its centrality
to Bub's thought. It is further argued that there is implicit in the quantum
information-theoretic tradition a set of ideas that mark a genuinely new
alternative to the framework of quantum logic. These ideas are of considerable
interest for the philosophy of quantum mechanics, a claim which I defend with
an extended discussion of their application to our understanding of the
philosophical significance of the no hidden variable theorem of Kochen and
Specker.Comment: Presented to the 2007 conference, New Directions in the Foundations
of Physic
Jump-like unravelings for non-Markovian open quantum systems
Non-Markovian evolution of an open quantum system can be `unraveled' into
pure state trajectories generated by a non-Markovian stochastic (diffusive)
Schr\"odinger equation, as introduced by Di\'osi, Gisin, and Strunz. Recently
we have shown that such equations can be derived using the modal (hidden
variable) interpretation of quantum mechanics. In this paper we generalize this
theory to treat jump-like unravelings. To illustrate the jump-like behavior we
consider a simple system: A classically driven (at Rabi frequency )
two-level atom coupled linearly to a three mode optical bath, with a central
frequency equal to the frequency of the atom, , and the two side
bands have frequencies . In the large limit we
observed that the jump-like behavior is similar to that observed in this system
with a Markovian (broad band) bath. This is expected as in the Markovian limit
the fluorescence spectrum for a strongly driven two level atom takes the form
of a Mollow triplet. However the length of time for which the Markovian-like
behaviour persists depends upon {\em which} jump-like unraveling is used.Comment: 11 pages, 5 figure
Solving the measurement problem: de Broglie-Bohm loses out to Everett
The quantum theory of de Broglie and Bohm solves the measurement problem, but
the hypothetical corpuscles play no role in the argument. The solution finds a
more natural home in the Everett interpretation.Comment: 20 pages; submitted to special issue of Foundations of Physics, in
honour of James T. Cushin
Modality, Potentiality and Contradiction in Quantum Mechanics
In [11], Newton da Costa together with the author of this paper argued in
favor of the possibility to consider quantum superpositions in terms of a
paraconsistent approach. We claimed that, even though most interpretations of
quantum mechanics (QM) attempt to escape contradictions, there are many hints
that indicate it could be worth while to engage in a research of this kind.
Recently, Arenhart and Krause [1, 2, 3] have raised several arguments against
this approach and claimed that, taking into account the square of opposition,
quantum superpositions are better understood in terms of contrariety
propositions rather than contradictory propositions. In [17] we defended the
Paraconsistent Approach to Quantum Superpositions (PAQS) and provided arguments
in favor of its development. In the present paper we attempt to analyze the
meanings of modality, potentiality and contradiction in QM, and provide further
arguments of why the PAQS is better suited, than the Contrariety Approach to
Quantum Superpositions (CAQS) proposed by Arenhart and Krause, to face the
interpretational questions that quantum technology is forcing us to consider.Comment: Published in: New Directions in Paraconsistent Logic, J-Y B\'eziau M.
Chakraborty & S. Dutta (Eds.), Springer, in press. arXiv admin note: text
overlap with arXiv:1404.518
Quantum and classical descriptions of a measuring apparatus
A measuring apparatus is described by quantum mechanics while it interacts
with the quantum system under observation, and then it must be given a
classical description so that the result of the measurement appears as
objective reality. Alternatively, the apparatus may always be treated by
quantum mechanics, and be measured by a second apparatus which has such a dual
description. This article examines whether these two different descriptions are
mutually consistent. It is shown that if the dynamical variable used in the
first apparatus is represented by an operator of the Weyl-Wigner type (for
example, if it is a linear coordinate), then the conversion from quantum to
classical terminology does not affect the final result. However, if the first
apparatus encodes the measurement in a different type of operator (e.g., the
phase operator), the two methods of calculation may give different results.Comment: 18 pages LaTeX (including one encapsulated PostScript figure
Grounding Bohmian Mechanics in Weak Values and Bayesianism
Bohmian mechanics (BM) is a popular interpretation of quantum mechanics in
which particles have real positions. The velocity of a point x in configuration
space is defined as the standard probability current j(x) divided by the
probability density P(x). However, this ``standard'' j is in fact only one of
infinitely many that transform correctly and satisfy \dot P + \del . j=0. In
this article I show that there is a unique j that can be determined
experimentally as a weak value using techniques that would make sense to a
classical physicist. Moreover, this operationally defined j equals the standard
j, so, assuming \dot x = j/P, the possible Bohmian paths can also be determined
experimentally from a large enough ensemble. Furthermore, this approach to
deriving BM singles out x as the hidden variable, because (for example) the
operationally defined momentum current is in general incompatible with the
evolution of the momentum distribution. Finally I discuss how, in this setting,
the usual quantum probabilities can be derived from a Bayesian standpoint, via
the principle of indifference.Comment: 11 page
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