32,433 research outputs found
On the measure of nonclassicality of field states
The degree of nonclassicality of states of a field mode is analysed
considering both phase-space and distance-type measures of nonclassicality. By
working out some general examples, it is shown explicitly that the phase-space
measure is rather sensitive to superposition of states, with finite
superpositions possessing maximum nonclassical depth (the highest degree of
nonclassicality) irrespective to the nature of the component states. Mixed
states are also discussed and examples with nonclassical depth varying between
the minimum and the maximum allowed values are exhibited. For pure Gaussian
states, it is demonstrated that distance-type measures based on the
Hilbert-Schmidt metric are equivalent to the phase-space measure. Analyzing
some examples, it is shown that distance-type measures are efficient to
quantify the degree of nonclassicality of non-Gaussian pure states.Comment: Latex, 21 pages, 1 figur
A Potential Foundation for Emergent Space-Time
We present a novel derivation of both the Minkowski metric and Lorentz
transformations from the consistent quantification of a causally ordered set of
events with respect to an embedded observer. Unlike past derivations, which
have relied on assumptions such as the existence of a 4-dimensional manifold,
symmetries of space-time, or the constant speed of light, we demonstrate that
these now familiar mathematics can be derived as the unique means to
consistently quantify a network of events. This suggests that space-time need
not be physical, but instead the mathematics of space and time emerges as the
unique way in which an observer can consistently quantify events and their
relationships to one another. The result is a potential foundation for emergent
space-time.Comment: The paper was originally titled "The Physics of Events: A Potential
Foundation for Emergent Space-Time". We changed the title (and abstract) to
be more direct when the paper was accepted for publication at the Journal of
Mathematical Physics. 24 pages, 15 figure
Exact and Asymptotic Measures of Multipartite Pure State Entanglement
In an effort to simplify the classification of pure entangled states of multi
(m) -partite quantum systems, we study exactly and asymptotically (in n)
reversible transformations among n'th tensor powers of such states (ie n copies
of the state shared among the same m parties) under local quantum operations
and classical communication (LOCC). With regard to exact transformations, we
show that two states whose 1-party entropies agree are either locally-unitarily
(LU) equivalent or else LOCC-incomparable. In particular we show that two
tripartite Greenberger-Horne-Zeilinger (GHZ) states are LOCC-incomparable to
three bipartite Einstein-Podolsky-Rosen (EPR) states symmetrically shared among
the three parties. Asymptotic transformations result in a simpler
classification than exact transformations. We show that m-partite pure states
having an m-way Schmidt decomposition are simply parameterizable, with the
partial entropy across any nontrivial partition representing the number of
standard ``Cat'' states (|0^m>+|1^m>) asymptotically interconvertible to the
state in question. For general m-partite states, partial entropies across
different partitions need not be equal, and since partial entropies are
conserved by asymptotically reversible LOCC operations, a multicomponent
entanglement measure is needed, with each scalar component representing a
different kind of entanglement, not asymptotically interconvertible to the
other kinds. In particular the m=4 Cat state is not isentropic to, and
therefore not asymptotically interconvertible to, any combination of bipartite
and tripartite states shared among the four parties. Thus, although the m=4 cat
state can be prepared from bipartite EPR states, the preparation process is
necessarily irreversible, and remains so even asymptotically.Comment: 13 pages including 3 PostScript figures. v3 has updated references
and discussion, to appear Phys. Rev.
A Case Study on Logical Relations using Contextual Types
Proofs by logical relations play a key role to establish rich properties such
as normalization or contextual equivalence. They are also challenging to
mechanize. In this paper, we describe the completeness proof of algorithmic
equality for simply typed lambda-terms by Crary where we reason about logically
equivalent terms in the proof environment Beluga. There are three key aspects
we rely upon: 1) we encode lambda-terms together with their operational
semantics and algorithmic equality using higher-order abstract syntax 2) we
directly encode the corresponding logical equivalence of well-typed
lambda-terms using recursive types and higher-order functions 3) we exploit
Beluga's support for contexts and the equational theory of simultaneous
substitutions. This leads to a direct and compact mechanization, demonstrating
Beluga's strength at formalizing logical relations proofs.Comment: In Proceedings LFMTP 2015, arXiv:1507.0759
A Control-Oriented Notion of Finite State Approximation
We consider the problem of approximating discrete-time plants with
finite-valued sensors and actu- ators by deterministic finite memory systems
for the purpose of certified-by-design controller synthesis. Building on ideas
from robust control, we propose a control-oriented notion of finite state
approximation for these systems, demonstrate its relevance to the control
synthesis problem, and discuss its key features.Comment: IEEE Transactions on Automatic Control, to appea
Non-equivalence of antibiotic generic drugs and risk for intensive care patients
Background: The underlying axiom in applying generic drugs is the equivalence of their active ingredient with the (usually more expensive) innovator product, an all-embracing statement with the insidious result that physicians assume that the generic products have been subjected to the same rigorous testing regimens as the brand-name products. The present paper presents novel experimental data on an investigator-blinded comparison between the innovator imipenem antibiotic, and a number of its generics.
Methods: Particulate matter contamination of each group was visualized by means of a membrane filter method. Functional studies in an animal modelâthe dorsal skinfold chamber technique in mice-designed to simulate the state of microcirculatory dysfunction in intensive care patients was performed, in order to assess the influence of the particulate matter of each group on the functional capillary density of the striated skin muscle, after their intravenous injection.
Results: The results showed massive particulate contamination of the generics, in a size range relevant for impacting the microcirculation. The particulate contamination contributed in some generic groups to a significant shutdown of tissue perfusion.
Conclusion: The presented data underscore the need to raise the regulatory barriers for the entry of generics to the market, well beyond the simplistic proof of âbioequivalenceâ, which in no measure deals with the essential questions of quality and patient safety. If generics are used, they should be tested by a filter technique and optical microscopy, to ensure the absence especially of small particulate contaminants and their purity
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