356,239 research outputs found
Maltese educational broadcasting : education through the media and the media in education
Educational broadcasting has formed part of the broadcasting scene in Malta since 1948. Over the years it has passed, as far as responsibility is concerned, from the hands of one to another, including the Department of Information, the Malta Broadcasting Authority, Xandir Malta (Malta's state broadcasting system), and, as it is at present, the Department of Education, which falls under the Ministry of Education and the Environment.peer-reviewe
Asymmetric broadcasting of quantum correlations
In this work, we exhaustively investigate local and
nonlocal broadcasting of entanglement as well as correlations beyond
entanglement (geometric discord) using asymmetric Pauli cloners with most
general two qubit state as the resource. We exemplify asymmetric broadcasting
of entanglement using Maximally Entangled Mixed States. We demonstrate the
variation of broadcasting range with the amount of entanglement present in the
resource state as well as with the asymmetry in the cloner. We show that it is
impossible to optimally broadcast geometric discord with the help of these
asymmetric Pauli cloning machines. We also study the problem of broadcasting of entanglement using non-maximally entangled state (NME) as
the resource. For this task, we introduce a method we call successive
broadcasting which involves application of optimal cloning
machines multiple times. We compare and contrast the performance of this method
with the application of direct optimal cloning machines. We
show that optimal cloner does a better job at broadcasting
than the successive application of cloners and the successive
method can be beneficial in the absence of cloners. We also
bring out the fundamental difference between the tasks of cloning and
broadcasting in the final part of the manuscript. We create examples to show
that there exist local unitaries which can be employed to give a better range
for broadcasting. Such unitary operations are not only economical, but also
surpass the best possible range obtained using existing cloning machines
enabling broadcasting of lesser entangled states. This result opens up a new
direction in exploration of methods to facilitate broadcasting which may
outperform the standard strategies implemented through cloning transformations.Comment: Edited sections, changed figures, to be published in Physical Review
Exploiting spontaneous transmissions for broadcasting and leader election in radio networks
We study two fundamental communication primitives: broadcasting and leader election in the classical model of multi-hop radio networks with unknown topology and without collision detection mechanisms. It has been known for almost 20 years that in undirected networks with n nodes and diameter D, randomized broadcasting requires Ω(D log n/D + log2 n) rounds, assuming that uninformed nodes are not allowed to communicate (until they are informed). Only very recently, Haeupler and Wajc (PODC'2016) showed that this bound can be improved for the model with spontaneous transmissions, providing an O(D log n log log n/log D + logO(1) n)-time broadcasting algorithm. In this article, we give a new and faster algorithm that completes broadcasting in O(D log n/log D + logO(1) n) time, succeeding with high probability. This yields the first optimal O(D)-time broadcasting algorithm whenever n is polynomial in D.
Furthermore, our approach can be applied to design a new leader election algorithm that matches the performance of our broadcasting algorithm. Previously, all fast randomized leader election algorithms have used broadcasting as a subroutine and their complexity has been asymptotically strictly larger than the complexity of broadcasting. In particular, the fastest previously known randomized leader election algorithm of Ghaffari and Haeupler (SODA'2013) requires O(D log n/D min {log log n, log n/D} + logO(1) n)-time, succeeding with high probability. Our new algorithm again requires O(D log n/log D + logO(1) n) time, also succeeding with high probability
A generalized no-broadcasting theorem
We prove a generalized version of the no-broadcasting theorem, applicable to
essentially \emph{any} nonclassical finite-dimensional probabilistic model
satisfying a no-signaling criterion, including ones with ``super-quantum''
correlations. A strengthened version of the quantum no-broadcasting theorem
follows, and its proof is significantly simpler than existing proofs of the
no-broadcasting theorem.Comment: 4 page
Satellite Broadcasting Enabled Blockchain Protocol: A Preliminary Study
Low throughput has been the biggest obstacle of large-scale blockchain
applications. During the past few years, researchers have proposed various
schemes to improve the systems' throughput. However, due to the inherent
inefficiency and defects of the Internet, especially in data broadcasting
tasks, these efforts all rendered unsatisfactory. In this paper, we propose a
novel blockchain protocol which utilizes the satellite broadcasting network
instead of the traditional Internet for data broadcasting and consensus tasks.
An automatic resumption mechanism is also proposed to solve the unique
communication problems of satellite broadcasting. Simulation results show that
the proposed algorithm has a lower communication cost and can greatly improve
the throughput of the blockchain system. Theoretical estimation of a satellite
broadcasting enabled blockchain system's throughput is 6,000,000 TPS with a 20
gbps satellite bandwidth.Comment: Accepted by 2020 Information Communication Technologies Conference
(ICTC 2020
Superbroadcasting of mixed states
We derive the optimal universal broadcasting for mixed states of qubits. We
show that the nobroadcasting theorem cannot be generalized to more than a
single input copy. Moreover, for four or more input copies it is even possible
to purify the input states while broadcasting. We name such purifying
broadcasting superbroadcasting.Comment: 4 pages, 4 figures, to appear on Phys. Rev. Let
No-local-broadcasting theorem for quantum correlations
We prove that the correlations present in a multipartite quantum state have
an \emph{operational} quantum character as soon as the state does not simply
encode a multipartite classical probability distribution, i.e. does not
describe the joint state of many classical registers. Even unentangled states
may exhibit such \emph{quantumness}, that is pointed out by the new task of
\emph{local broadcasting}, i.e. of locally sharing pre-established
correlations: this task is feasible if and only if correlations are classical
and derive a no-local-broadcasting theorem for quantum correlations. Thus,
local broadcasting is able to point out the quantumness of correlations, as
standard broadcasting points out the quantum character of single system states.
Further, we argue that our theorem implies the standard no-broadcasting theorem
for single systems, and that our operative approach leads in a natural way to
the definition of measures for quantumness of correlations.Comment: 5 pages, various changes (title, shortened, references added,
corrected typos,...), submitte
Superbroadcasting of conjugate quantum variables
We consider the problem of broadcasting arbitrary states of radiation modes
from N to M>N copies by a map that preserves the average value of the field and
optimally reduces the total noise in conjugate variables. For N>=2 the
broadcasting can be achieved perfectly, and for sufficiently noisy input states
one can even purify the state while broadcasting--the so-called
superbroadcasting. For purification (i.e. M<=N), the reduction of noise is
independent of M. Similar results are proved for broadcasting with
phase-conjugation. All the optimal maps can be implemented by linear optics and
linear amplification.Comment: 7 pages, 1 eps figures. Accepted for publication on Europhysics
Letter
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