1,629 research outputs found
Separability in the Ambient Logic
The \it{Ambient Logic} (AL) has been proposed for expressing properties of
process mobility in the calculus of Mobile Ambients (MA), and as a basis for
query languages on semistructured data. We study some basic questions
concerning the discriminating power of AL, focusing on the equivalence on
processes induced by the logic . As underlying calculi besides MA we
consider a subcalculus in which an image-finiteness condition holds and that we
prove to be Turing complete. Synchronous variants of these calculi are studied
as well. In these calculi, we provide two operational characterisations of
: a coinductive one (as a form of bisimilarity) and an inductive one
(based on structual properties of processes). After showing to be stricly
finer than barbed congruence, we establish axiomatisations of on the
subcalculus of MA (both the asynchronous and the synchronous version), enabling
us to relate to structural congruence. We also present some
(un)decidability results that are related to the above separation properties
for AL: the undecidability of on MA and its decidability on the
subcalculus.Comment: logical methods in computer science, 44 page
When champions meet: Rethinking the Bohr--Einstein debate
Einstein's philosophy of physics (as clarified by Fine, Howard, and Held) was
predicated on his Trennungsprinzip, a combination of separability and locality,
without which he believed objectification, and thereby "physical thought" and
"physical laws", to be impossible. Bohr's philosophy (as elucidated by Hooker,
Scheibe, Folse, Howard, Held, and others), on the other hand, was grounded in a
seemingly different doctrine about the possibility of objective knowledge,
namely the necessity of classical concepts. In fact, it follows from Raggio's
Theorem in algebraic quantum theory that - within an appropriate class of
physical theories - suitable mathematical translations of the doctrines of Bohr
and Einstein are equivalent. Thus - upon our specific formalization - quantum
mechanics accommodates Einstein's Trennungsprinzip if and only if it is
interpreted a la Bohr through classical physics. Unfortunately, the
protagonists themselves failed to discuss their differences in this
constructive way, since their debate was dominated by Einstein's ingenious but
ultimately flawed attempts to establish the "incompleteness" of quantum
mechanics.
This aspect of their debate may still be understood and appreciated, however,
as reflecting a much deeper and insurmountable disagreement between Bohr and
Einstein on the knowability of Nature. Using the theological controversy on the
knowability of God as a analogy, Einstein was a Spinozist, whereas Bohr could
be said to be on the side of Maimonides. Thus Einstein's off-the-cuff
characterization of Bohr as a 'Talmudic philosopher' was spot-on.Comment: 22 pages. Argument sharpened and references update
The SOS Platform: Designing, Tuning and Statistically Benchmarking Optimisation Algorithms
open access articleWe present Stochastic Optimisation Software (SOS), a Java platform facilitating the algorithmic design process and the evaluation of metaheuristic optimisation algorithms. SOS reduces the burden of coding miscellaneous methods for dealing with several bothersome and time-demanding tasks such as parameter tuning, implementation of comparison algorithms and testbed problems, collecting and processing data to display results, measuring algorithmic overhead, etc. SOS provides numerous off-the-shelf methods including: (1) customised implementations of statistical tests, such as the Wilcoxon rank-sum test and the HolmâBonferroni procedure, for comparing the performances of optimisation algorithms and automatically generating result tables in PDF and formats; (2) the implementation of an original advanced statistical routine for accurately comparing couples of stochastic optimisation algorithms; (3) the implementation of a novel testbed suite for continuous optimisation, derived from the IEEE CEC 2014 benchmark, allowing for controlled activation of the rotation on each testbed function. Moreover, we briefly comment on the current state of the literature in stochastic optimisation and highlight similarities shared by modern metaheuristics inspired by nature. We argue that the vast majority of these algorithms are simply a reformulation of the same methods and that metaheuristics for optimisation should be simply treated as stochastic processes with less emphasis on the inspiring metaphor behind them
Overcoming Noise in Entanglement Distribution
Noise can be considered the natural enemy of quantum information. An often
implied benefit of high-dimensional entanglement is its increased resilience to
noise. However, manifesting this potential in an experimentally meaningful
fashion is challenging and has never been done before. In infinite dimensional
spaces, discretisation is inevitable and renders the effective dimension of
quantum states a tunable parameter. Owing to advances in experimental
techniques and theoretical tools, we demonstrate an increased resistance to
noise by identifying two pathways to exploit high-dimensional entangled states.
Our study is based on two separate experiments utilising canonical
spatio-temporal properties of entangled photon pairs. Following these different
pathways to noise resilience, we are able to certify entanglement in the
photonic orbital-angular-momentum and energy-time degrees of freedom up to
noise conditions corresponding to a noise fraction of 72 % and 92 %
respectively. Our work paves the way towards practical quantum communication
systems that are able to surpass current noise and distance limitations, while
not compromising on potential device-independence.Comment: 12 pages main text, 7 pages supplementary information, 6 figure
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