[Todos] Coloquios Extraordinarios DF de la próxima semana

[Augusto Roncaglia]

COLOQUIOS EXTRAORDINARIOS DEL DEPARTAMENTO DE FÍSICA EXACTAS - UBA


         En el AULA SEMINARIO, 2do piso, Pab. I,

          1- Lunes 3/12 - 14hs
              RAJARSHI ROY (University of Maryland)
              *Random Numbers from Light:  Photons, Time delays, Chaos and
Entropy*

          2- Martes 4/12 - 11hs
              YELENA GURYANOVA (IQOQI Vienna)
              *Ideal Projective Measurements Have Infinite Resource Costs*

          3- Martes 4/12 - 14hs
              ALBERT DIAZ-GUILERA (Universitat de Barcelona)
              *Nonlinear dynamics in multiplex networks*

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Rajarshi Roy
University of Maryland

*Random Numbers from Light:  Photons, Time delays, Chaos and Entropy*

Many physical processes, including the intensity fluctuations of a chaotic
laser, the detection of single photons, and the Brownian motion of a
microscopic particle in a fluid are unpredictable, at least on long
timescales. This unpredictability can be due to a  variety of physical
mechanisms, but it is quantified by an entropy rate. This rate, which
describes how quickly a system produces new and random information, is
fundamentally important in statistical mechanics and practically important
for random number generation. We experimentally study entropy generation
and the emergence of deterministic chaotic dynamics from discrete noise in
a system that applies feedback to a weak optical signal at the
single-photon level. We show that in this system the dynamics transition
from shot noise to chaos as the photon rate increases and that the entropy
rate can reflect either the deterministic or noisy aspects of the system
depending on the sampling rate and resolution of the measurements.
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Yelena Guryanova
IQOQI Vienna

*Ideal Projective Measurements Have Infinite Resource Costs*

We show that it is impossible to perform ideal projective measurements on
quantum systems using finite resources. We identify three fundamental
features of an ideal projective measurement and show that when limited by
finite resources only one of these features can be salvaged. Using an
explicit model of an N-particle detector perfectly reproducing the
statistics of the system, we provide tight analytic expressions for the
energy cost of performing a measurement. This cost may be broken down into
two parts. First, the cost of preparing the pointer in a suitable state,
and second, the cost of a global interaction between the system and pointer
in order to correlate them. Our results show that, even under the
assumption that the interaction can be controlled perfectly, achieving
perfect correlation is infinitely expensive. We provide protocols for
achieving optimal correlation given finite resources.

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Albert Diaz-Guilera
Universitat de Barcelona.

*Nonlinear dynamics in multiplex networks*

We will show some of the recent result in our group concerning dynamics in
multiplex networks. On the one hand we consider multiplex networks as set
of nodes in different
layers. At each layer the set of nodes is the same but the connections
among the nodes can be different in the layers.Furthermore the connections
among the layers is described by a ”network of layers”. We have studied
different processes across the layers (diffusion) and between the layers
(reaction) [1]. In this case Turing patterns appear as an ef-
fect of different average connectivities in different layers [2].
We also show that a multiplex construction where the layers correspond to
contexts in which agents make different sets of connections can make a
model of opinion formation to show stationary states of coexistence that
are not observed in simple layers [3]. Finally, as a particular case of
multiplex network, one can also analyze networks that change in time, since
in this case each layer of the multiplex corresponds to a snapshot of the
interaction pattern. For this situation, we have shown that there are
different mechanisms that dominate the diffusion of information in the
system depending on the relative effect of mobility and diffusion among the
nodes

[1] Replicator dynamics with diffusion on multiplex networks. RJ Requejo,
A. Diaz-Guilera. Physical Review E 94, 022301 (2016)
[2] Pattern formation in multiplex networks. NE Kouvaris, S Hata, A.
Diaz-Guilera. Scientific Reports 5, Article number: 10840 (2015)
[3] Opinion competition dynamics on multiplex networks. R Amato, N E
Kouvaris, M San Miguel and Albert Diaz-Guilera. New J Phys 19, 123019
(2017).
[4] Tuning Synchronization of Integrate-and-Fire Oscillators through
Mobility. L. Prignano, O. Sagarra, and A. DAaz-Guilera  ̃Phys. Rev. Lett.
110, 114101 (2013)
[5] Synchronization in dynamical networks of locally coupled self-propelled
oscillators. D. Levis, I. Pagonabarraga,
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