1,981 research outputs found
Observing different quantum trajectories in cavity QED
The experimental observation of quantum jumps is an example of single open
quantum systems that, when monitored, evolve in terms of stochastic
trajectories conditioned on measurements results. Here we present a proposal
that allows the experimental observation of a much larger class of quantum
trajectories in cavity QED systems. In particular, our scheme allows for the
monitoring of engineered thermal baths that are crucial for recent proposals
for probing entanglement decay and also for entanglement protection. The scheme
relies on the interaction of a three-level atom and a cavity mode that
interchangeably play the roles of system and probe. If the atom is detected the
evolution of the cavity fields follows quantum trajectories and vice-versa.Comment: 5 pages, 2 figure
Random walk on random walks: low densities
We consider a random walker in a dynamic random environment given by a system
of independent simple symmetric random walks. We obtain ballisticity results
under two types of perturbations: low particle density, and strong local drift
on particles. Surprisingly, the random walker may behave very differently
depending on whether the underlying environment particles perform lazy or
non-lazy random walks, which is related to a notion of permeability of the
system. We also provide a strong law of large numbers, a functional central
limit theorem and large deviation bounds under an ellipticity condition.Comment: 28 page
Distant entanglement protected through artificially increased local temperature
In composed quantum systems, the presence of local dissipative channels
causes loss of coherence and entanglement at a rate that grows with the
temperature of the reservoirs. However, here we show that if temperature is
artificially added to the system, entanglement decay can be significantly
slowed down or even suppressed conditioned on suitable local monitoring of the
reservoirs. We propose a scheme to implement the joint reservoir monitoring
applicable in different experimental setups like trapped ions, circuit and
cavity QED or quantum dots coupled to nanowires and we analyze its general
robustness against detection inefficiencies and non-zero temperature of the
natural reservoir
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Random walk on random walks: Low densities
We consider a random walker in a dynamic random environment given by a
system of independent simple symmetric random walks. We obtain ballisticity
results under two types of perturbations: low particle density, and strong
local drift on particles. Surprisingly, the random walker may behave very
differently depending on whether the underlying environment particles perform
lazy or non-lazy random walks, which is related to a notion of permeability
of the system. We also provide a strong law of large numbers, a functional
central limit theorem and large deviation bounds under an ellipticity
condition
Random walk on random walks: Higher dimensions
We study the evolution of a random walker on a conservative dynamic
random environment composed of independent particles performing simple
symmetric random walks, generalizing results of [16] to higher dimensions and
more general transition kernels without the assumption of uniform ellipticity
or nearest-neighbour jumps. Specifically, we obtain a strong law of large
numbers, a functional central limit theorem and large deviation estimates for
the position of the random walker under the annealed law in a high density
regime. The main obstacle is the intrinsic lack of monotonicity in
higher-dimensional, non-nearest neighbour settings. Here we develop more
general renormalization and renewal schemes that allow us to overcome this
issue. As a second application of our methods, we provide an alternative
proof of the ballistic behaviour of the front of (the discrete-time version
of) the infection model introduced in [23]
Accessibility of physical states and non-uniqueness of entanglement measure
Ordering physical states is the key to quantifying some physical property of
the states uniquely. Bipartite pure entangled states are totally ordered under
local operations and classical communication (LOCC) in the asymptotic limit and
uniquely quantified by the well-known entropy of entanglement. However, we show
that mixed entangled states are partially ordered under LOCC even in the
asymptotic limit. Therefore, non-uniqueness of entanglement measure is
understood on the basis of an operational notion of asymptotic convertibility.Comment: 8 pages, 1 figure. v2: main result unchanged but presentation
extensively changed. v3: figure added, minor correction
Purification and Preliminary Crystallographic Analysis of a New Lys49-PLA2 from B. Jararacussu
BjVIII is a new myotoxic Lys49-PLA2 isolated from Bothrops jararacussu venom that exhibits atypical effects on human platelet aggregation. To better understand the mode of action of BjVIII, crystallographic studies were initiated. Two crystal forms were obtained, both containing two molecules in the asymmetric unit (ASU). Synchrotron radiation diffraction data were collected to 2.0 Å resolution and 1.9 Å resolution for crystals belonging to the space group P212121 (a = 48.4 Å, b = 65.3 Å, c = 84.3 Å) and space group P3121 (a = b = 55.7 Å, c = 127.9 Å), respectively. Refinement is currently in progress and the refined structures are expected to shed light on the unusual platelet aggregation activity observed for BjVIII
Belief Dynamics in Complex Social Networks
People are becoming increasingly more connected to each other in social media networks. These networks are complex because in general there can be many di fferent types of relations, as well as di fferent degrees of strength for each one; moreover, these relations are dynamic because they can change over time. In this context, users' knowledge flows over the network, and modeling how this occurs - or can possibly occur - is therefore of great interest from a knowledge representation and reasoning perspective. In this paper, we focus on the problem of how a single user's knowledge base changes when exposed to a stream of news items coming from other members in the network. As a first step towards solving this problem, we identify possible solutions leveraging preexisting belief merging operators, and conclude that there is a gap that needs to be bridged between the application of such operators and a principled solution to the proposed problem.Sociedad Argentina de Informática e Investigación Operativa (SADIO
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