Realization of a photonic controlled-NOT gate sufficient for quantum computation

We report the first experimental demonstration of a quantum controlled-NOT gate for different photons, which is classically feed forwardable. In the experiment, we achieved this goal with only the use of linear optics, an entangled ancillary pair of photons, and postselection. The techniques developed in our experiment are of significant importance for quantum information processing with linear optics.     

A simple, inexpensive, and precise magic angle spinning speed controller

Certain magic-angle spinning heteronuclear dipolar recoupling experiments using rotor-synchronized pulse trains require very precise control of the sample-spinning rate. An inexpensive spinning speed controller for use in magic-angle solid-state NMR experiments is described which can control the spinning rate to within +/- 0.2 Hz. The apparatus is based on a simple micro-controller and is self-contained. Experimental results are presented that show the importance of good spinning speed control.     

Dendritic macromers as in situ polymerizing biomaterials for securing cataract incisions

Dendritic macromers are attractive macromolecules for hydrogel formation since high cross-linking densities at low polymer concentration can be obtained, varied physical properties can be observed based on the macromer structure, and low viscous aqueous solutions can be injected in an in vivo site of irregular shaped to form a well-integrated polymer network. A peptide dendron possessing terminal cysteine residues was synthesized and characterized. When this peptide dendron was mixed with poly(ethylene glycol dialdehyde) in aqueous solution at pH = 7.4, a hydrogel spontaneously formed as a consequence of thiazolidine linkages between the macromers. Such in situ polymerized hydrogels are of interest for tissue engineering and wound-repair applications. To evaluate the potential use of this hydrogel sealant in ophthalmic surgeries, a 3-mm clear corneal incision (i.e., the wounds created during a typical cataract surgery) was successfully sealed.     

Resource-efficient linear optical quantum computation

We introduce a scheme for linear optics quantum computation, that makes no use of teleported gates, and requires stable interferometry over only the coherence length of the photons. We achieve a much greater degree of efficiency and a simpler implementation than previous proposals. We follow the "cluster state" measurement based quantum computational approach, and show how cluster states may be efficiently generated from pairs of maximally polarization entangled photons using linear optical elements. We demonstrate the universality and usefulness of generic parity measurements, as well as introducing the use of redundant encoding of qubits to enable utilization of destructive measurements--both features of use in a more general context.     

Quadrupole deformation of the self-conjugate nucleus 72Kr

We report on the first determination of the absolute B(E2;0+(1)-->2+(1)) excitation strength in the N=Z nucleus 72Kr. 72Kr is the heaviest N=Z nucleus for which this quantity has been measured and provides a benchmark in a region of the nuclear chart dominated by rapidly changing deformations and shapes mediated by the interplay of strongly oblate and prolate-driving orbitals. The deduced quadrupole deformation strength is in agreement with a variety of self-consistent models that predict an oblate shape for the ground state of 72Kr. Large-scale shell-model Monte Carlo calculations reproduce the experimental B(E2) value and link the result to the occupation of the deformation-driving g9/2 orbit.     

Galois relations on knot invariants

We discuss the existence of Galois relations obeyed by certain link invariants. Some of these relations have recently been identified and exploited within the context of conformal field theory and Lie/Kac-Moody representation theory. These relations should aid in computing knot invariants. They probably have an interpretation in terms of quasitriangular (quasi) Hopf algebras. They could also have a topological interpretation, and may serve as a concrete model for related ideas of Grothendieck, Drinfeld, Degiovanni, Ihara, and others.     

Auditory spatial discrimination by barn owls in simulated echoic conditions

In humans, directional hearing in reverberant conditions is characterized by a "precedence effect," whereby directional information conveyed by leading sounds dominates perceived location, and listeners are relatively insensitive to directional information conveyed by lagging sounds. Behavioral studies provide evidence of precedence phenomena in a wide range of species. The present study employs a discrimination paradigm, based on habituation and recovery of the pupillary dilation response, to provide quantitative measures of precedence phenomena in the barn owl. As in humans, the owl's ability to discriminate changes in the location of lagging sources is impaired relative to that for single sources. Spatial discrimination of lead sources is also impaired, but to a lesser extent than discrimination of lagging sources. Results of a control experiment indicate that sensitivity to monaural cues cannot account for discrimination of lag source location. Thus, impairment of discrimination ability in the two-source conditions most likely reflects a reduction in sensitivity to binaural directional information. These results demonstrate a similarity of precedence effect phenomena in barn owls and humans, and provide a basis for quantitative comparison with neuronal data from the same species.     

Observation of velocity-independent electron transport in the reversed field pinch

Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas in the Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have been used to determine the velocity dependence of the electron diffusion coefficient, utilizing computational solutions of the Fokker-Planck transport equation. With improved-confinement, the fast electron diffusivity drops by 2 orders of magnitude and is independent of velocity. This suggests a change in the transport mechanism away from stochastic magnetic field diffusion.