18,463 research outputs found
Exact Results on Dynamical Decoupling by -Pulses in Quantum Information Processes
The aim of dynamical decoupling consists in the suppression of decoherence by
appropriate coherent control of a quantum register. Effectively, the
interaction with the environment is reduced. In particular, a sequence of
pulses is considered. Here we present exact results on the suppression of the
coupling of a quantum bit to its environment by optimized sequences of
pulses. The effect of various cutoffs of the spectral density of the
environment is investigated. As a result we show that the harder the cutoff is
the better an optimized pulse sequence can deal with it. For cutoffs which are
neither completely hard nor very soft we advocate iterated optimized sequences.Comment: 12 pages and 3 figure
Constraining a bulk viscous matter-dominated cosmological model using SNe Ia, CMB and LSS
We present and constrain a cosmological model which component is a
pressureless fluid with bulk viscosity as an explanation for the present
accelerated expansion of the universe. We study the particular model of a
constant bulk viscosity coefficient \zeta_m. The possible values of \zeta_m are
constrained using the cosmological tests of SNe Ia Gold 2006 sample, the CMB
shift parameter R from the three-year WMAP observations, the Baryon Acoustic
Oscillation (BAO) peak A from the Sloan Digital Sky Survey (SDSS) and the
Second Law of Thermodynamics (SLT). It was found that this model is in
agreement with the SLT using only the SNe Ia test. However when the model is
submitted to the three cosmological tests together (SNe+CMB+BAO) the results
are: 1.- the model violates the SLT, 2.- predicts a value of H_0 \approx 53 km
sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- we obtain a bad fit to data
with a \chi^2_{min} \approx 400 (\chi^2_{d.o.f.} \approx 2.2). These results
indicate that this model is ruled out by the observations.Comment: 4 pages, 1 figure. Work presented in the XI Mexican Workshop on
Particles and Fields, Tuxtla Gutierrez, Mexico, nov 7-12, 2007. Submitted to
AIP Conference Proceedings of this conferenc
Android Malware Clustering through Malicious Payload Mining
Clustering has been well studied for desktop malware analysis as an effective
triage method. Conventional similarity-based clustering techniques, however,
cannot be immediately applied to Android malware analysis due to the excessive
use of third-party libraries in Android application development and the
widespread use of repackaging in malware development. We design and implement
an Android malware clustering system through iterative mining of malicious
payload and checking whether malware samples share the same version of
malicious payload. Our system utilizes a hierarchical clustering technique and
an efficient bit-vector format to represent Android apps. Experimental results
demonstrate that our clustering approach achieves precision of 0.90 and recall
of 0.75 for Android Genome malware dataset, and average precision of 0.98 and
recall of 0.96 with respect to manually verified ground-truth.Comment: Proceedings of the 20th International Symposium on Research in
Attacks, Intrusions and Defenses (RAID 2017
Estimativas das probabilidades de reconcepção em matrizes no Pantanal da Nhecolândia.
O objetivo deste estudo foi estimar a probabilidade de reconcepção em matrizes criadas na sub-região da Nhecolândia em função do mês de parição e condições climáticas no período de fecundação. The aim of this study was to estimate the probability of reconception in cows reared in the Nhecolândia sub-region, according to the month of calving and the weather conditions during the period of fertilization
Seleção e descarte de matrizes no Pantanal.
bitstream/CPAP/56312/1/ADM101.pdfFormato eletrônico
Manipulation of the dynamics of many-body systems via quantum control methods
We investigate how dynamical decoupling methods may be used to manipulate the
time evolution of quantum many-body systems. These methods consist of sequences
of external control operations designed to induce a desired dynamics. The
systems considered for the analysis are one-dimensional spin-1/2 models, which,
according to the parameters of the Hamiltonian, may be in the integrable or
non-integrable limits, and in the gapped or gapless phases. We show that an
appropriate control sequence may lead a chaotic chain to evolve as an
integrable chain and a system in the gapless phase to behave as a system in the
gapped phase. A key ingredient for the control schemes developed here is the
possibility to use, in the same sequence, different time intervals between
control operations.Comment: 10 pages, 3 figure
Atomic Fermi gas in the trimerized Kagom\'e lattice at the filling 2/3
We study low temperature properties of an atomic spinless interacting Fermi
gas in the trimerized Kagom\'e lattice for the case of two fermions per trimer.
The system is described by a quantum spin 1/2 model on the triangular lattice
with couplings depending on bonds directions. Using exact diagonalizations we
show that the system exhibits non-standard properties of a {\it quantum
spin-liquid crystal}, combining a planar antiferromagnetic order with an
exceptionally large number of low energy excitations.Comment: 4 pages & 4 figures + 2 tables, better version of Fig.
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