2,264 research outputs found
Lensless wide-field fluorescent imaging on a chip using compressive decoding of sparse objects.
We demonstrate the use of a compressive sampling algorithm for on-chip fluorescent imaging of sparse objects over an ultra-large field-of-view (>8 cm(2)) without the need for any lenses or mechanical scanning. In this lensfree imaging technique, fluorescent samples placed on a chip are excited through a prism interface, where the pump light is filtered out by total internal reflection after exciting the entire sample volume. The emitted fluorescent light from the specimen is collected through an on-chip fiber-optic faceplate and is delivered to a wide field-of-view opto-electronic sensor array for lensless recording of fluorescent spots corresponding to the samples. A compressive sampling based optimization algorithm is then used to rapidly reconstruct the sparse distribution of fluorescent sources to achieve approximately 10 microm spatial resolution over the entire active region of the sensor-array, i.e., over an imaging field-of-view of >8 cm(2). Such a wide-field lensless fluorescent imaging platform could especially be significant for high-throughput imaging cytometry, rare cell analysis, as well as for micro-array research
A Tutorial on Clique Problems in Communications and Signal Processing
Since its first use by Euler on the problem of the seven bridges of
K\"onigsberg, graph theory has shown excellent abilities in solving and
unveiling the properties of multiple discrete optimization problems. The study
of the structure of some integer programs reveals equivalence with graph theory
problems making a large body of the literature readily available for solving
and characterizing the complexity of these problems. This tutorial presents a
framework for utilizing a particular graph theory problem, known as the clique
problem, for solving communications and signal processing problems. In
particular, the paper aims to illustrate the structural properties of integer
programs that can be formulated as clique problems through multiple examples in
communications and signal processing. To that end, the first part of the
tutorial provides various optimal and heuristic solutions for the maximum
clique, maximum weight clique, and -clique problems. The tutorial, further,
illustrates the use of the clique formulation through numerous contemporary
examples in communications and signal processing, mainly in maximum access for
non-orthogonal multiple access networks, throughput maximization using index
and instantly decodable network coding, collision-free radio frequency
identification networks, and resource allocation in cloud-radio access
networks. Finally, the tutorial sheds light on the recent advances of such
applications, and provides technical insights on ways of dealing with mixed
discrete-continuous optimization problems
Generation of Universal Linear Optics by Any Beamsplitter
In 1994, Reck et al. showed how to realize any unitary transformation on a
single photon using a product of beamsplitters and phaseshifters. Here we show
that any single beamsplitter that nontrivially mixes two modes, also densely
generates the set of unitary transformations (or orthogonal transformations, in
the real case) on the single-photon subspace with m>=3 modes. (We prove the
same result for any two-mode real optical gate, and for any two-mode optical
gate combined with a generic phaseshifter.) Experimentally, this means that one
does not need tunable beamsplitters or phaseshifters for universality: any
nontrivial beamsplitter is universal for linear optics. Theoretically, it means
that one cannot produce "intermediate" models of linear optical computation
(analogous to the Clifford group for qubits) by restricting the allowed
beamsplitters and phaseshifters: there is a dichotomy; one either gets a
trivial set or else a universal set. No similar classification theorem for
gates acting on qubits is currently known. We leave open the problem of
classifying optical gates that act on three or more modes.Comment: 14 pages; edited Lemma 3.3 and updated references. Results are
unchange
An extensive English language bibliography on graph theory and its applications, supplement 1
Graph theory and its applications - bibliography, supplement
Cluster-state quantum computation
This article is a short introduction to and review of the cluster-state model
of quantum computation, in which coherent quantum information processing is
accomplished via a sequence of single-qubit measurements applied to a fixed
quantum state known as a cluster state. We also discuss a few novel properties
of the model, including a proof that the cluster state cannot occur as the
exact ground state of any naturally occurring physical system, and a proof that
measurements on any quantum state which is linearly prepared in one dimension
can be efficiently simulated on a classical computer, and thus are not
candidates for use as a substrate for quantum computation.Comment: 15 pages, resubmitted version accepted to Rev. Math. Phy
Quantum Discord and Quantum Computing - An Appraisal
We discuss models of computing that are beyond classical. The primary
motivation is to unearth the cause of nonclassical advantages in computation.
Completeness results from computational complexity theory lead to the
identification of very disparate problems, and offer a kaleidoscopic view into
the realm of quantum enhancements in computation. Emphasis is placed on the
`power of one qubit' model, and the boundary between quantum and classical
correlations as delineated by quantum discord. A recent result by Eastin on the
role of this boundary in the efficient classical simulation of quantum
computation is discussed. Perceived drawbacks in the interpretation of quantum
discord as a relevant certificate of quantum enhancements are addressed.Comment: To be published in the Special Issue of the International Journal of
Quantum Information on "Quantum Correlations: entanglement and beyond." 11
pages, 4 figure
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