15,368 research outputs found
Entanglement production by quantum error correction in the presence of correlated environment
We analyze the effect of a quantum error correcting code on the entanglement
of encoded logical qubits in the presence of a dephasing interaction with a
correlated environment. Such correlated reservoir introduces entanglement
between physical qubits. We show that for short times the quantum error
correction interprets such entanglement as errors and suppresses it. However
for longer time, although quantum error correction is no longer able to correct
errors, it enhances the rate of entanglement production due to the interaction
with the environment.Comment: 7 pages, 3 figures, published versio
Obfuscation-based malware update: A comparison of manual and automated methods
Indexación: Scopus; Web of Science.This research presents a proposal of malware classification and its update based on capacity and obfuscation. This article is an extension of [4]a, and describes the procedure for malware updating, that is, to take obsolete malware that is already detectable by antiviruses, update it through obfuscation techniques and thus making it undetectable again. As the updating of malware is generally performed manually, an automatic solution is presented together with a comparison from the standpoint of cost and processing time. The automated method proved to be more reliable, fast and less intensive in the use of resources, specially in terms of antivirus analysis and malware functionality checking times.http://univagora.ro/jour/index.php/ijccc/article/view/2961/112
Extraction of Singlet States from Noninteracting High-Dimensional Spins
We present a scheme for the extraction of singlet states of two remote
particles of arbitrary quantum spin number. The goal is achieved through
post-selection of the state of interaction mediators sent in succession. A
small number of iterations is sufficient to make the scheme effective. We
propose two suitable experimental setups where the protocol can be implemented.Comment: 4 pages, 2 figure
An efficient flamelet progress-variable method for modeling non-premixed flames in weak electric fields
Combustion stabilization and enhancement of the flammability limits are
mandatory objectives to improve nowadays combustion chambers. At this purpose,
the use of an electric field in the flame region provides a solution which is,
at the same time, easy to implement and effective to modify the flame
structure. The present work describes an efficient flamelet progress-variable
approach developed to model the fluid dynamics of flames immersed in an
electric field. The main feature of this model is that it can use complex
ionization mechanisms without increasing the computational cost of the
simulation. The model is based on the assumption that the combustion process is
not directly influenced by the electric field and has been tested using two
chemi-ionization mechanisms of different complexity in order to examine its
behavior with and without the presence of heavy anions in the mixture. Using a
one- and two-dimensional numerical test cases, the present approach has been
able to reproduce all the major aspects encountered when a flame is subject to
an imposed electric field and the main effects of the different chemical
mechanisms. Moreover, the proposed model is shown to produce a large reduction
in the computational cost, being able to shorten the time needed to perform a
simulation up to 40 times.Comment: 26 pages, 13 figures, paper accepted for publication on Computers and
Fluid
Physical model for the generation of ideal resources in multipartite quantum networking
We propose a physical model for generating multipartite entangled states of
spin- particles that have important applications in distributed quantum
information processing. Our protocol is based on a process where mobile spins
induce the interaction among remote scattering centers. As such, a major
advantage lies on the management of stationary and well separated spins. Among
the generable states, there is a class of -qubit singlets allowing for
optimal quantum telecloning in a scalable and controllable way. We also show
how to prepare Aharonov, W and Greenberger-Horne-Zeilinger states.Comment: 5 pages, 2 figures. Format revise
Risk factor disclosures in the US Airline Industry following the COVID-19 pandemic
This study examines how airlines in the United States report risk at a difficult and uncertain time as a result of the COVID-19 pandemic. The fundamental differences between the years 2019 and 2020 are identified using Leximancer, which is used to locate the key ideas and themes addressed in the risk reporting sections. Following the pandemic, the themes that addressed generic and recurring hazards were afforded less weight than themes that highlighted risks particular to day-to-day business and the stock market. The findings also point to the need for corporations to disclose future-oriented risks more fully in post-COVID-19 reporting, with an emphasis on unpredictability, stock volatility, and operational disruption. This study adds to the body of knowledge on risk profiling, particularly as it relates to the airline business, and it offers stakeholders and investors a glimpse into the general concerns of airlines. The inherent information imbalance between management and investors is lessened and transparency is increased because of this improved understanding of the market.info:eu-repo/semantics/publishedVersio
Entanglement-induced electron coherence in a mesoscopic ring with two magnetic impurities
We investigate the Aharonov-Bohm (AB) interference pattern in the electron
transmission through a mesoscopic ring in which two identical non-interacting
magnetic impurities are embedded. Adopting a quantum waveguide theory, we
derive the exact transmission probability amplitudes and study the influence of
maximally entangled states of the impurity spins on the electron transmittivity
interference pattern. For suitable electron wave vectors, we show that the
amplitude of AB oscillations in the absence of impurities is in fact not
reduced within a wide range of the electron-impurity coupling constant when the
maximally entangled singlet state is prepared. Such state is thus able to
inhibit the usual electron decoherence due to scattering by magnetic
impurities. We also show how this maximally entangled state of the impurity
spins can be generated via electron scattering.Comment: 8 page
A method to find quantum noiseless subsystems
We develop a structure theory for decoherence-free subspaces and noiseless
subsystems that applies to arbitrary (not necessarily unital) quantum
operations. The theory can be alternatively phrased in terms of the
superoperator perspective, or the algebraic noise commutant formalism. As an
application, we propose a method for finding all such subspaces and subsystems
for arbitrary quantum operations. We suggest that this work brings the
fundamental passive technique for error correction in quantum computing an
important step closer to practical realization.Comment: 5 pages, to appear in Physical Review Letter
Combining historical and geological data for the assessment of the landslide hazard: a case study from Campania, Italy
International audiencePast slope instabilities at Quindici (one of the five towns of Campania that was hit by catastrophic landslides on 5 May 1998) and in the Lauro Valley are investigated to improve the understanding of the landslide history in the area, as a mandatory step for the evaluation of the landslide hazard. The research was performed by combining information on past slope instabilities from both historical and geological data. From numerous historical sources an archive consisting of 45 landsliding and flooding events for the period 1632?1998 was compiled. Landslide activity was also investigated by means of interpretation of multi-year sets of aerial photos, production of Landslide Activity Maps, and excavation of trenches on the alluvial fans at the mountain foothills. Detailed stratigraphic analysis of the sections exposed in the trenches identified landslide events as the main geomorphic process responsible for building up the fans in the study area. Integration of historical and geological approaches provides significant insight into past and recent instability at Quindici. This is particularly valuable in view of the limitations of individual sources of information. Application of such an approach offers potential for improved hazard assessment and risk mitigation
Berry phase for a spin 1/2 in a classical fluctuating field
The effect of fluctuations in the classical control parameters on the Berry
phase of a spin 1/2 interacting with a adiabatically cyclically varying
magnetic field is analyzed. It is explicitly shown that in the adiabatic limit
dephasing is due to fluctuations of the dynamical phase.Comment: 4 pages, 1 figure, published versio
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