23,899 research outputs found
Double-Edge Factor Graphs: Definition, Properties, and Examples
Some of the most interesting quantities associated with a factor graph are
its marginals and its partition sum. For factor graphs \emph{without cycles}
and moderate message update complexities, the sum-product algorithm (SPA) can
be used to efficiently compute these quantities exactly. Moreover, for various
classes of factor graphs \emph{with cycles}, the SPA has been successfully
applied to efficiently compute good approximations to these quantities. Note
that in the case of factor graphs with cycles, the local functions are usually
non-negative real-valued functions. In this paper we introduce a class of
factor graphs, called double-edge factor graphs (DE-FGs), which allow local
functions to be complex-valued and only require them, in some suitable sense,
to be positive semi-definite. We discuss various properties of the SPA when
running it on DE-FGs and we show promising numerical results for various
example DE-FGs, some of which have connections to quantum information
processing.Comment: Submitte
Estimating the Information Rate of a Channel with Classical Input and Output and a Quantum State (Extended Version)
We consider the problem of transmitting classical information over a
time-invariant channel with memory. A popular class of time-invariant channels
with memory are finite-state-machine channels, where a \emph{classical} state
evolves over time and governs the relationship between the classical input and
the classical output of the channel. For such channels, various techniques have
been developed for estimating and bounding the information rate. In this paper
we consider a class of time-invariant channels where a \emph{quantum} state
evolves over time and governs the relationship between the classical input and
the classical output of the channel. We propose algorithms for estimating and
bounding the information rate of such channels. In particular, we discuss
suitable graphical models for doing the relevant computations.Comment: This is an extended version of a paper that appears in Proc. 2017
IEEE International Symposium on Information Theory, Aachen, Germany, June
201
Bounding and Estimating the Classical Information Rate of Quantum Channels with Memory
We consider the scenario of classical communication over a finite-dimensional
quantum channel with memory using a separable-state input ensemble and local
output measurements. We propose algorithms for estimating the information rate
of such communication setups, along with algorithms for bounding the
information rate based on so-called auxiliary channels. Some of the algorithms
are extensions of their counterparts for (classical) finite-state-machine
channels. Notably, we discuss suitable graphical models for doing the relevant
computations. Moreover, the auxiliary channels are learned in a data-driven
approach; i.e., only input/output sequences of the true channel are needed, but
not the channel model of the true channel.Comment: This work has been submitted to the IEEE Transactions on Information
Theory for possible publication. Copyright may be transferred without notice,
after which this version may no longer be accessibl
The Microscopic Structure of Adsorbed Water on Hydrophobic Surfaces under Ambient Conditions
The interaction of water vapor with hydrophobic surfaces is poorly understood. We utilize graphene templating to preserve and visualize the microscopic structures of adsorbed water on hydrophobic surfaces. Three well-defined surfaces [H–Si(111), graphite, and functionalized mica] were investigated, and water was found to adsorb as nanodroplets (~10–100 nm in size) on all three surfaces under ambient conditions. The adsorbed nanodroplets were closely associated with atomic-scale surface defects and step-edges and wetted all the hydrophobic substrates with contact angles < ~10°, resulting in total water adsorption that was similar to what is found for hydrophilic surfaces. These results point to the significant differences between surface processes at the atomic/nanometer scales and in the macroscopic world
Recycle-GAN: Unsupervised Video Retargeting
We introduce a data-driven approach for unsupervised video retargeting that
translates content from one domain to another while preserving the style native
to a domain, i.e., if contents of John Oliver's speech were to be transferred
to Stephen Colbert, then the generated content/speech should be in Stephen
Colbert's style. Our approach combines both spatial and temporal information
along with adversarial losses for content translation and style preservation.
In this work, we first study the advantages of using spatiotemporal constraints
over spatial constraints for effective retargeting. We then demonstrate the
proposed approach for the problems where information in both space and time
matters such as face-to-face translation, flower-to-flower, wind and cloud
synthesis, sunrise and sunset.Comment: ECCV 2018; Please refer to project webpage for videos -
http://www.cs.cmu.edu/~aayushb/Recycle-GA
Non-Markovian coherence dynamics of driven spin boson model: damped quantum beat or large amplitude coherence oscillation
The dynamics of driven spin boson model is studied analytically by means of
the perturbation approach based on a unitary transformation. We gave the
analytical expression for the population difference and coherence of the two
level system. The results show that in the weak driven case, the population
difference present damped coherent oscillation (single or double frequency) and
the frequencies depend on the initial state. The coherence exhibit damped
oscillation with Rabi frequency. When driven field is strong enough, the
population difference exhibit undamped large-amplitude coherent oscillation.
The results easily return to the two extreme cases without dissipation or
without periodic driven.Comment: 15 pages,5 figure
Controlling a triangular flexible formation of autonomous agents
In formation control, triangular formations consisting of three autonomous
agents serve as a class of benchmarks that can be used to test and compare the
performances of different controllers. We present an algorithm that combines
the advantages of both position- and distance-based gradient descent control
laws. For example, only two pairs of neighboring agents need to be controlled,
agents can work in their own local frame of coordinates and the orientation of
the formation with respect to a global frame of coordinates is not prescribed.
We first present a novel technique based on adding artificial biases to
neighboring agents' range sensors such that their eventual positions correspond
to a collinear configuration. Right after, a small modification in the bias
terms by introducing a prescribed rotation matrix will allow the control of the
bearing of the neighboring agents.Comment: 7 pages, accepted in the 20th World Congress of the International
Federation of Automatic Control (IFAC
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