2,934 research outputs found
Generation of graph-state streams
We propose a protocol to generate a stream of mobile qubits in a graph state
through a single stationary parent qubit and discuss two types of its physical
implementation, namely, the generation of photonic graph states through an
atom-like qubit and those of flying atoms through a cavity-mode photonic qubit.
The generated graph states fall into an important class that can hugely reduce
the resource requirement of fault-tolerant linear optics quantum computation,
which was previously known to be far from realistic. In regard to the flying
atoms, we also propose a heralded generation scheme, which allows for
high-fidelity graph states even under the photon loss.Comment: Accepted for publication at PRA Rapid Communication
Quantum Simulations of Relativistic Quantum Physics in Circuit QED
We present a scheme for simulating relativistic quantum physics in circuit
quantum electrodynamics. By using three classical microwave drives, we show
that a superconducting qubit strongly-coupled to a resonator field mode can be
used to simulate the dynamics of the Dirac equation and Klein paradox in all
regimes. Using the same setup we also propose the implementation of the
Foldy-Wouthuysen canonical transformation, after which the time derivative of
the position operator becomes a constant of the motion.Comment: 13 pages, 3 figure
Who Contributes to the Knowledge Sharing Economy?
Information sharing dynamics of social networks rely on a small set of
influencers to effectively reach a large audience. Our recent results and
observations demonstrate that the shape and identity of this elite, especially
those contributing \emph{original} content, is difficult to predict.
Information acquisition is often cited as an example of a public good. However,
this emerging and powerful theory has yet to provably offer qualitative
insights on how specialization of users into active and passive participants
occurs.
This paper bridges, for the first time, the theory of public goods and the
analysis of diffusion in social media. We introduce a non-linear model of
\emph{perishable} public goods, leveraging new observations about sharing of
media sources. The primary contribution of this work is to show that
\emph{shelf time}, which characterizes the rate at which content get renewed,
is a critical factor in audience participation. Our model proves a fundamental
\emph{dichotomy} in information diffusion: While short-lived content has simple
and predictable diffusion, long-lived content has complex specialization. This
occurs even when all information seekers are \emph{ex ante} identical and could
be a contributing factor to the difficulty of predicting social network
participation and evolution.Comment: 15 pages in ACM Conference on Online Social Networks 201
Amphibians and squamate reptiles from the latest early Pleistocene of Cueva Victoria (Murcia, southeastern Spain, SW Mediterranean): Paleobiogeographic and paleoclimatic implications
The karstic filling of Cueva Victoria in southeastern Spain, dated from the latest early Pleistocene (ca. 1.1 Ma), is famous for providing primate fossil remains (Theropithecus) of typical African origin, in the general controversy on the antiquity of the first hominid settlements in Western Europe and their possible entrance into Europe through the Strait of Gibraltar. Cueva Victoria has also furnished the following fauna of anurans and squamate reptiles: cf. Pelodytes sp. (Pelodytidae), Bufo cf. B. bufo (Bufonidae), Blanus cinereus (Blanidae), Tarentola sp. (Geckonidae), Chalcides cf. Ch. bedriagai (Scincidae), Timon cf. T. lepidus and indeterminate small lacertids (Lacertidae), Natrix maura, Coronella girondica, Rhinechis scalaris and Malpolon cf. M. monspessulanus (Colubridae). This faunal association seems to suggest a mean annual temperature slightly fresher than nowadays (approximately 1°C less than at present in the area), with cooler winters but warmer summers and above all higher mean annual precipitations (+ 400 mm). The landscape may correspond to an open forest environment of a Mediterranean type, with some still water points
Automated data reduction workflows for astronomy
Data from complex modern astronomical instruments often consist of a large
number of different science and calibration files, and their reduction requires
a variety of software tools. The execution chain of the tools represents a
complex workflow that needs to be tuned and supervised, often by individual
researchers that are not necessarily experts for any specific instrument. The
efficiency of data reduction can be improved by using automatic workflows to
organise data and execute the sequence of data reduction steps. To realize such
efficiency gains, we designed a system that allows intuitive representation,
execution and modification of the data reduction workflow, and has facilities
for inspection and interaction with the data. The European Southern Observatory
(ESO) has developed Reflex, an environment to automate data reduction
workflows. Reflex is implemented as a package of customized components for the
Kepler workflow engine. Kepler provides the graphical user interface to create
an executable flowchart-like representation of the data reduction process. Key
features of Reflex are a rule-based data organiser, infrastructure to re-use
results, thorough book-keeping, data progeny tracking, interactive user
interfaces, and a novel concept to exploit information created during data
organisation for the workflow execution. Reflex includes novel concepts to
increase the efficiency of astronomical data processing. While Reflex is a
specific implementation of astronomical scientific workflows within the Kepler
workflow engine, the overall design choices and methods can also be applied to
other environments for running automated science workflows.Comment: 12 pages, 7 figure
On the p-length of some finite p-soluble groups
The main aim of this paper is to give structural information of a finite group of minimal order belonging to a subgroup-closed class of finite groups and whose p-length is greater than 1, p a prime number. Alternative proofs and improvements of recent results about the influence of minimal p-subgroups on the p-nilpotence and p-length of a finite group arise as consequences of our study
Long-range surface plasmon polariton excitation at the quantum level
We provide the quantum mechanical description of the excitation of long-range
surface plasmon polaritons (LRSPPs) on thin metallic strips. The excitation
process consists of an attenuated-reflection setup, where efficient
photon-to-LRSPP wavepacket-transfer is shown to be achievable. For calculating
the coupling, we derive the first quantization of LRSPPs in the polaritonic
regime. We study quantum statistics during propagation and characterize the
performance of photon-to-LRSPP quantum state transfer for single-photons,
photon-number states and photonic coherent superposition states.Comment: 9 pages, 6 figures, RevTeX4; Accepted versio
Precise Complexity of the Core in Dichotomous and Additive Hedonic Games
Hedonic games provide a general model of coalition formation, in which a set
of agents is partitioned into coalitions, with each agent having preferences
over which other players are in her coalition. We prove that with additively
separable preferences, it is -complete to decide whether a core- or
strict-core-stable partition exists, extending a result of Woeginger (2013).
Our result holds even if valuations are symmetric and non-zero only for a
constant number of other agents. We also establish -completeness of
deciding non-emptiness of the strict core for hedonic games with dichotomous
preferences. Such results establish that the core is much less tractable than
solution concepts such as individual stability.Comment: ADT-2017, 15 pages in LNCS styl
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