230 research outputs found
On the dragging of light by a rotating medium
When light is passing through a rotating medium the optical polarization is rotated. Recently, it has been reasoned that this rotation applies also to the transmitted image. We examine these two phenomena by extending an analysis of Player (Player 1976 Proc. R. Soc. A 349, 441-445) to general electromagnetic fields. We find that in this more general case, the wave equation inside the rotating medium has to be amended by a term which is connected to the orbital angular momentum (OAM) of the light. We show that optical spin and OAM account for the rotation of the polarization and the rotation of the transmitted image, respectively
Optical orbital angular momentum
We present a brief introduction to the orbital angular momentum of light, the subject of our theme issue and, in particular, to the developments in the 13 years following the founding paper by Allen et al. (Allen et al. 1992 Phys. Rev. A 45, 8185 (doi:10.1103/PhysRevA.45.8185)). The papers by our invited authors serve to bring the field up to date and suggest where developments may take us next
Fourier relationship between angular position and optical orbital angular momentum
We demonstrate the Fourier relationship between angular position and angular
momentum for a light mode. In particular we measure the distribution of orbital
angular momentum states of light that has passed through an aperture and verify
that the orbital angular momentum distribution is given by the complex
Fourier-transform of the aperture function. We use spatial light modulators,
configured as diffractive optical components, to define the initial orbital
angular momentum state of the beam, set the defining aperture, and measure the
angular momentum spread of the resulting beam. These measurements clearly
confirm the Fourier relationship between angular momentum and angular position,
even at light intensities corresponding to the single photon level.Comment: 4 pages, 4 figure
Quantum-inspired computational imaging
Computational imaging combines measurement and computational methods with the aim of forming images even when the measurement conditions are weak, few in number, or highly indirect. The recent surge in quantum-inspired imaging sensors, together with a new wave of algorithms allowing on-chip, scalable and robust data processing, has induced an increase of activity with notable results in the domain of low-light flux imaging and sensing. We provide an overview of the major challenges encountered in low-illumination (e.g., ultrafast) imaging and how these problems have recently been addressed for imaging applications in extreme conditions. These methods provide examples of the future imaging solutions to be developed, for which the best results are expected to arise from an efficient codesign of the sensors and data analysis tools.Y.A. acknowledges support from the UK Royal Academy of Engineering under the Research Fellowship Scheme (RF201617/16/31). S.McL. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grant EP/J015180/1). V.G. acknowledges support from the U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office award W911NF-10-1-0404, the U.S. DARPA REVEAL program through contract HR0011-16-C-0030, and U.S. National Science Foundation through grants 1161413 and 1422034. A.H. acknowledges support from U.S. Army Research Office award W911NF-15-1-0479, U.S. Department of the Air Force grant FA8650-15-D-1845, and U.S. Department of Energy National Nuclear Security Administration grant DE-NA0002534. D.F. acknowledges financial support from the UK Engineering and Physical Sciences Research Council (grants EP/M006514/1 and EP/M01326X/1). (RF201617/16/31 - UK Royal Academy of Engineering; EP/J015180/1 - UK Engineering and Physical Sciences Research Council; EP/M006514/1 - UK Engineering and Physical Sciences Research Council; EP/M01326X/1 - UK Engineering and Physical Sciences Research Council; W911NF-10-1-0404 - U.S. Defense Advanced Research Projects Agency (DARPA) InPho program through U.S. Army Research Office; HR0011-16-C-0030 - U.S. DARPA REVEAL program; 1161413 - U.S. National Science Foundation; 1422034 - U.S. National Science Foundation; W911NF-15-1-0479 - U.S. Army Research Office; FA8650-15-D-1845 - U.S. Department of the Air Force; DE-NA0002534 - U.S. Department of Energy National Nuclear Security Administration)Accepted manuscrip
Quantum correlations in position, momentum, and intermediate bases for a full optical field of view
We report an eight-element, linear-array, single-photon detector that uses multiple fibers of differing lengths coupled to a single detector, the timing information from which reveals the position in which the photon was measured. Using two such arrays and two detectors we measure the correlations of photons produced by parametric downconversion, without recourse to mechanical scanning. Spatial light modulators acting as variable focal length lenses positioned between the downconversion crystal and the arrays allow us to switch between measurement of position, transverse momentum, or intermediate bases. We observe the product of the variances of the conditional probabilities for position and momentum to be more than an order of magnitude below the classical limit, realizing a full-field demonstration of the Einstein-Podolsky-Rosen paradox. Such, multistate measurement technologies allow access to the higher information content of the photon based upon spatial modes
3D Computational Ghost Imaging
Computational ghost imaging retrieves the spatial information of a scene
using a single pixel detector. By projecting a series of known random patterns
and measuring the back reflected intensity for each one, it is possible to
reconstruct a 2D image of the scene. In this work we overcome previous
limitations of computational ghost imaging and capture the 3D spatial form of
an object by using several single pixel detectors in different locations. From
each detector we derive a 2D image of the object that appears to be illuminated
from a different direction, using only a single digital projector as
illumination. Comparing the shading of the images allows the surface gradient
and hence the 3D form of the object to be reconstructed. We compare our result
to that obtained from a stereo- photogrammetric system utilizing multiple high
resolution cameras. Our low cost approach is compatible with consumer
applications and can readily be extended to non-visible wavebands.Comment: 13pages, 4figure
Testing for entanglement with periodic coarse-graining
Continuous variables systems find valuable applications in quantum
information processing. To deal with an infinite-dimensional Hilbert space, one
in general has to handle large numbers of discretized measurements in tasks
such as entanglement detection. Here we employ the continuous transverse
spatial variables of photon pairs to experimentally demonstrate novel
entanglement criteria based on a periodic structure of coarse-grained
measurements. The periodization of the measurements allows for an efficient
evaluation of entanglement using spatial masks acting as mode analyzers over
the entire transverse field distribution of the photons and without the need to
reconstruct the probability densities of the conjugate continuous variables.
Our experimental results demonstrate the utility of the derived criteria with a
success rate in entanglement detection of relative to studied
cases.Comment: V1: revtex4, 10 pages, 4 figures + supp. material (4 pages, 1 figure)
V2: Substantial revisions implemented both in theory and experimental data
analysi
Proceedings of the 39th Annual Meeting, Southern Soybean Disease Workers (March 7-8, 2012, Pensacola Beach, Florida)
Contents
Symposium: Soybean Nematodes: Their Status, Impact and Management
The Current Status of Nematodes of Soybean in Louisiana and Arkansas. Charles Overstreet, Edward C McGawley, Melea Martin, and Terry Kirkpatrick
A Molecular Analysis of Resistance of Soybean to the Soybean Cyst Nematode. Vincent Klink
Racism in Nematology. Terry Niblack
SCN-resistant Soybeans, HG types, Yield, and SCN Reproduction: How It All Comes Together in the Field in Iowa. Gregory Tylka
Soybean Lines Evaluated for Resistance to Reniform Nematode. Sally Stetina
Graduate student presentations (Boyd Padgett, moderator)
Fungicide Resistance in Cercospora kikuchii, a Major Pathogen of Louisiana Soybean. Trey Price
Variation in the Internal Transcribed Spacer (ITS) Region within Phakopsora pachyrhizi and Implications for the Currently Used Molecular Diagnostic Assays. Tomas Rush
Theoretical Disease and Decision Model for Fungicide Applications for Soybean Rust. Heather Marie Young
Relationship Between Stink Bug Damaged Soybean Seed and Incidence of Phomopsis longicolla in the Mississippi Soybean Production System. Joshua Jones, Angus Catchot, Fred Musser, Tom Allen, Maria Tomaso-Peterson, and Jeff Gore, lV
Spatial Assessment of Rhizoctonia solani In Fields Undergoing Rice/Soybean Rotations. TN Spurlock, CS Rothrock, and WS Monfort
Thursday, March 8th session (Danise Beadle, moderator)
Sustaining the Pest Information Platform for Extension and Education with Support from Industry (I-PIPE). Scott Isard
Screening Germplasm for Resistance to Phomopsis Seed Decay: Joint Effort from USDA and University Scientists. Shuxian Li, Gabe Sciumbato, Pengyin Chen, John Rupe, Allen Wrather, James R Smith and Randall L Nelson
Effect of Storage on Soybean Seed Quality and Emergence. John Rupe
Foliar Fungicides to Prevent Yield Loss Attributed to Aerial Web Blight in Mississippi, 2010 and 2011. Tom Allen, Alan Blaine, Bernie White, and Billy Moore
Mycovirus-induced Hypovirulence as an Alternative Means to Control Fungal Diseases of Soybean. Said A Ghabrial and Jiatao Xie
Managing Cercospora Blight in Louisiana: Facing New Challenges. Boyd Padgett, Trey Price, Brooks Blanche, Ray Schneider, Clayton Hollier, and Myra Purvis
Seasonal Progress of Charcoal Rot and Its Impact on Soybean Productivity. Alemu Mengistu
Discussion session: Soybean Disease Resistance (Clayton Hollier, moderator)
Fungicide Resistance in Cercospora sojina: Chapter 2. Carl A Bradley and Guirong R Zhang
Fungicide Efficacy on Strobilurin Resistant Cercospora sojina (Frogeye Leaf Spot) in Soybean. Melvin Newman
Strobilurin Resistance in Rhizoctonia solani in Soybeans in Louisiana. Clayton A. Hollier
Southern United States Soybean Disease Loss Estimate for 2011. Compiled by Stephen R. Koennin
Angular two-photon interference and angular two-qubit states
Using angular-position-orbital-angular-momentum entangled photons, we study angular two-photon interference in a scheme in which entangled photons are made to pass through apertures in the form of double angular slits, and using this scheme, we demonstrate an entangled two-qubit state that is based on the angular-position correlations of entangled photons. The entanglement of the two-qubit state is quantified in terms of concurrence. These results provide an additional means for preparing entangled quantum states for use in quantum information protocols
Adaptive foveated single-pixel imaging with dynamic super-sampling
As an alternative to conventional multi-pixel cameras, single-pixel cameras
enable images to be recorded using a single detector that measures the
correlations between the scene and a set of patterns. However, to fully sample
a scene in this way requires at least the same number of correlation
measurements as there are pixels in the reconstructed image. Therefore
single-pixel imaging systems typically exhibit low frame-rates. To mitigate
this, a range of compressive sensing techniques have been developed which rely
on a priori knowledge of the scene to reconstruct images from an under-sampled
set of measurements. In this work we take a different approach and adopt a
strategy inspired by the foveated vision systems found in the animal kingdom -
a framework that exploits the spatio-temporal redundancy present in many
dynamic scenes. In our single-pixel imaging system a high-resolution foveal
region follows motion within the scene, but unlike a simple zoom, every frame
delivers new spatial information from across the entire field-of-view. Using
this approach we demonstrate a four-fold reduction in the time taken to record
the detail of rapidly evolving features, whilst simultaneously accumulating
detail of more slowly evolving regions over several consecutive frames. This
tiered super-sampling technique enables the reconstruction of video streams in
which both the resolution and the effective exposure-time spatially vary and
adapt dynamically in response to the evolution of the scene. The methods
described here can complement existing compressive sensing approaches and may
be applied to enhance a variety of computational imagers that rely on
sequential correlation measurements.Comment: 13 pages, 5 figure
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