6,007 research outputs found
Intermediate quantum maps for quantum computation
We study quantum maps displaying spectral statistics intermediate between
Poisson and Wigner-Dyson. It is shown that they can be simulated on a quantum
computer with a small number of gates, and efficiently yield information about
fidelity decay or spectral statistics. We study their matrix elements and
entanglement production, and show that they converge with time to distributions
which differ from random matrix predictions. A randomized version of these maps
can be implemented even more economically, and yields pseudorandom operators
with original properties, enabling for example to produce fractal random
vectors. These algorithms are within reach of present-day quantum computers.Comment: 4 pages, 4 figures, research done at
http://www.quantware.ups-tlse.fr
Survival of current in a periodically driven hard-core bosonic system
We study the survival of the current induced initially by applying a twist at
the boundary of a chain of hard-core bosons (HCBs), subject to a periodic
double -function kicks in the staggered on-site potential. We study the
current flow and the work-done on the system at the long-time limit as a
function of the driving frequency. Like a recent observation in the HCB chain
with single -function kick in the staggered on-site potential, here we
also observe many dips in the current flow and concurrently many peaks in the
work-done on the system at some specific values of the driving frequency.
However, unlike the single kicked case, here we do not observe a complete
disappearance of the current in the limit of a high driving frequency, which
shows the absence of any dynamical localization in the double
-functions kicked HCB chain. Our analytical estimations of the
saturated current and the saturated work-done, defined at the limit of a large
time together with a high driving frequency, match very well with the exact
numerics. In the case of the very small initial current, induced by a very
small twist , we observe that the saturated current is proportional to
. Finally, we study the time-evolution of the half-filled HCB chain where
the particles are localized in the central part of the chain. We observe that
the particles spread linearly in a light-cone like region at the rate
determined by the maximum value of the group velocity. Except for a very
trivial case, the maximum group velocity never vanishes, and therefore we do
not observe any dynamical localization in the system.Comment: 11 pages, 9 figure
Multi-agent system for dynamic manufacturing system optimization
This paper deals with the application of multi-agent system concept for optimization of dynamic uncertain process. These problems are known to have a computationally demanding objective function, which could turn to be infeasible when large problems are considered. Therefore, fast approximations to the objective function are required. This paper employs bundle of intelligent systems algorithms tied together in a multi-agent system. In order to demonstrate the system, a metal reheat furnace scheduling problem is adopted for highly demanded optimization problem. The proposed multi-agent approach has been evaluated for different settings of the reheat furnace scheduling problem. Particle Swarm Optimization, Genetic Algorithm with different classic and advanced versions: GA with chromosome differentiation, Age GA, and Sexual GA, and finally a Mimetic GA, which is based on combining the GA as a global optimizer and the PSO as a local optimizer. Experimentation has been performed to validate the multi-agent system on the reheat furnace scheduling problem
Testing statistical bounds on entanglement using quantum chaos
Previous results indicate that while chaos can lead to substantial entropy
production, thereby maximizing dynamical entanglement, this still falls short
of maximality. Random Matrix Theory (RMT) modeling of composite quantum
systems, investigated recently, entails an universal distribution of the
eigenvalues of the reduced density matrices. We demonstrate that these
distributions are realized in quantized chaotic systems by using a model of two
coupled and kicked tops. We derive an explicit statistical universal bound on
entanglement, that is also valid for the case of unequal dimensionality of the
Hilbert spaces involved, and show that this describes well the bounds observed
using composite quantized chaotic systems such as coupled tops.Comment: 5 pages, 3 figures, to appear in PRL. New title. Revised abstract and
some changes in the body of the pape
Solar neutrinos: global analysis with day and night spectra from SNO
We perform global analysis of the solar neutrino data including the day and
night spectra of events at SNO. In the context of two active neutrino mixing,
the best fit of the data is provided by the LMA MSW solution with Delta m^2 =
6.15 10^{-5} eV^2, tan^2\theta = 0.41, f_B = 1.05, where f_B is the boron
neutrino flux in units of the corresponding flux in the Standard Solar Model
(SSM). At 3 sigma level we find the following upper bounds: tan^2\theta < 0.84
and Delta m^2 < 3.6 10^{-4} eV^2. From 1 sigma-interval we expect the day-night
asymmetries of the charged current and electron scattering events to be:
A_{DN}^{CC} = 3.9 +3.6-2.9 and A_{DN}^{ES} = 2.1 +2.1-1.4. The only other
solution which appears at 3 sigma-level is the VAC solution with Delta m^2 =
4.5 10^{-10} eV^2, tan^2\theta = 2.1 and f_B=0.75. The best fit point in the
LOW region, with Delta m^2 = 0.93 10^{-7} eV^2 and tan^2\theta = 0.64, is
accepted at 99.95% (3.5 sigma) C.L. . The least chi^2 point from the SMA
solution region, with Delta m^2 = 4.6 10^{-6} eV^2 and tan^2\theta = 5 10^{-4},
could be accepted at 5.5 sigma-level only. In the three neutrino context the
influence of theta_{13} is studied. We find that with increase of theta_{13}
the LMA best fit point shifts to larger Delta m^2, mixing angle is practically
unchanged, and the quality of the fit becomes worse. The fits of LOW and SMA
slightly improve. Predictions for KamLAND experiment (total rates, spectrum
distortion) have been calculated.Comment: Typos corrected, reference adde
Entanglement production in Quantized Chaotic Systems
Quantum chaos is a subject whose major goal is to identify and to investigate
different quantum signatures of classical chaos. Here we study entanglement
production in coupled chaotic systems as a possible quantum indicator of
classical chaos. We use coupled kicked tops as a model for our extensive
numerical studies. We find that, in general, presence of chaos in the system
produces more entanglement. However, coupling strength between two subsystems
is also very important parameter for the entanglement production. Here we show
how chaos can lead to large entanglement which is universal and describable by
random matrix theory (RMT). We also explain entanglement production in coupled
strongly chaotic systems by deriving a formula based on RMT. This formula is
valid for arbitrary coupling strengths, as well as for sufficiently long time.
Here we investigate also the effect of chaos on the entanglement production for
the mixed initial state. We find that many properties of the mixed state
entanglement production are qualitatively similar to the pure state
entanglement production. We however still lack an analytical understanding of
the mixed state entanglement production in chaotic systems.Comment: 16 pages, 5 figures. To appear in Pramana:Journal of Physic
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