Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with accidentals subtracted.Comment: 4 pages, 7 color figures. Revised manuscript includes the following changes: corrected pair generation rate from 44,000/s/mW pump to 123,000/s/mW pump; replaced Fig. 1b to enhance clarity; minor alterations to the title, abstract and introduction; grammatical correction

Generation of Pure-State Single-Photon Wavepackets by Conditional Preparation Based on Spontaneous Parametric Downconversion

We study the conditional preparation of single photons based on parametric downconversion, where the detection of one photon from a given pair heralds the existence of a single photon in the conjugate mode. We derive conditions on the modal characteristics of the photon pairs, which ensure that the conditionally prepared single photons are quantum-mechanically pure. We propose specific experimental techniques that yield photon pairs ideally suited for single-photon conditional preparation.Comment: 14 pages, 6 figure

Generation of multi-modal dialogue for a net environment

In this paper an architecture and special purpose markup language for simulated affective face-to-face communication is presented. In systems based on this architecture, users will be able to watch embodied conversational agents interact with each other in virtual locations on the internet. The markup language, or Rich Representation Language (RRL), has been designed to provide an integrated representation of speech, gesture, posture and facial animation

UV induces resistance in Arabidopsis Thaliana to the Oomycete Pathogen Hyaloperonospora Parasitica

Owing to their sessile nature, plants have evolved mechanisms to minimise the damaging effects of abiotic and biotic stresses. Attack by pathogenic fungi, viruses and bacterium is a major type of biotic stress. To resist infection, plants recognise invading pathogens and induce disease resistance through multiple signal transduction pathways. In addition, appropriate stimulation can cause plants to increase their resistance to future pathogen attack. We have found that exposure to non-lethal doses of UV-C (254 nm) renders a normally susceptible ecotype of Arabidopsis thaliana resistant to the biotrophic Oomycete pathogen Hyaloperonospora parasitica. The UV treatment induces an incompatible response in a dose-dependent fashion, and is still effective upon pathogen inoculation up to seven days after UV exposure. The degree of resistance diminishes with time but higher doses result in greater levels of resistance, even after seven days. Furthermore, the effect is systemic, occurring in parts of the plant that have not been irradiated. Incubation in the dark post?irradiation and prior to infection reduces the UV dose required to generate a specific level of pathogen resistance without affecting the duration of resistance. These observations, plus the inability of plants to photoreactivate UV photoproducts in the dark, strongly suggest that DNA damage induces the resistance phenotype. Currently, we are assessing the influence of DNA repair defects on UV-induced resistance, following the expression of a number of defence?related genes post-UV-C irradiation, and assessing the effect of UV in plant mutants deficient in specific signalling molecules involved in resistance.<br /

Rapid offline isotopic characterisation of hydrocarbon gases generated by micro scale sealed vessel pyrolysis

The method of offline coupling of micro scale sealed vessel pyrolysis (MSSV-Py) and gas chromatography-isotopic ratio mass spectrometry (GC-IRMS) was developed using a purpose built gas sampling device. The sampling device allows multiple GC and GC-IRMS injections to quantify the molecular composition and isotopic evolution of hydrocarbon gases (n-C1 to n-C5) generated by artificial maturation of sedimentary organic matter. Individual MSSV tubes were introduced into the gas sampling device, which was then evacuated to remove air and filled with helium at atmospheric pressure. The tube was crushed using a plunger after which the device was heated at 120 °C for 1 min to thermally mobilize and equilibrate the generated gas products. Aliquots of the gas phase were sampled using a gas tight syringe and analysed via GC-FID and GC-IRMS. Hydrocarbon gas yields using this technique have been calculated and compared with those obtained previously by online MSSV pyrolysis of the same samples under the same conditions. The major objective of this study was to investigate the potential isotopic fractionation of generated gaseous hydrocarbons within the gas sampling device as a function of time and temperature. For this purpose several tests using a standard gas mixture have been performed on the GC-IRMS. The analyses showed no isotopic fractionation of C1–5 hydrocarbons within 1 hour, minor δ13C enrichment after 5 hours, and significant enrichment after 22 hours for all the compounds at a temperature of 120 °C

Generation of correlated photons in controlled spatial modes by down-conversion in nonlinear waveguides

We report the observation of correlated photon pairs generated by spontaneous parametric down-conversion in a quasi-phase matched KTiOPO4 nonlinear waveguide. The highest ratio of coincidence to single photon count rates observed in the 830 nm wavelength region exceeds 18%. This makes nonlinear waveguides a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the down-converted photons produced in multimode waveguide structures.Comment: 4 pages, REVTe

Attention allocation in a language with post-focal prominences

Accentuation influences selective attention and the depth of semantic processing during online speech comprehension. We investigated the processing of semantically congruent and incongruent words in a language that presents cues to prosodic prominences in the region of the utterance occurring after the focussed information (the post-focal region). This language is Italian, in particular the variety spoken in Bari. In this variety, questions have a compressed, post-focal accent, whereas in statements there is a low-level pitch in this position. Using event-related potentials, we investigated the processing of congruent and incongruent target words with two prosodic realizations (focussed with accentuation, post-focal realization) and in two-sentence modalities (statement, question). Results indicate an N400 congruence effect that was modulated by position (focal, post-focal) and modality (statement, question): processing was deeper for questions in narrow focus than in post-focal position, while statements showed similar pronounced N400 effects across positions. The attenuated N400 difference for post-focal targets in questions was accompanied by a more enhanced late positivity when they were incongruent, indicating that attentional resources are allocated during updating of speech act information

Eudaimonistic Argumentation

Virtue theories have lately enjoyed a modest vogue in the study of argumentation, echoing the success of more far-reaching programmes in ethics and epistemology. Virtue theories of argumentation (VTA) comprise several conceptually distinct projects, including the provision of normative foundations for argument evaluation and a renewed focus on the character of good arguers. Perhaps the boldest of these is the pursuit of the fully satisfying argument, the argument that contributes to human flourishing. This project has an independently developed epistemic analogue: eudaimonistic virtue epistemology. Both projects stress the importance of widening the range of cognitive goals beyond, respectively, cogency and knowledge; both projects emphasize social factors, the right sort of community being indispensable for the cultivation of the intellectual virtues necessary to each project. This paper proposes a unification of the two projects by arguing that the intellectual good life sought by eudaimonistic virtue epistemologists is best realized through the articulation of an account of argumentation that contributes to human flourishing

Nonclassical 2-photon interference with separate intrinsically narrowband fibre sources

In this paper, we demonstrate a source of photon pairs based on four-wave-mixing in photonic crystal fibres. Careful engineering of the phase matching conditions in the fibres enables us to create photon pairs at 597 nm and 860 nm in an intrinsically factorable state showing no spectral correlations. This allows for heralding one photon in a pure state and hence renders narrow band filtering obsolete. The source is narrow band, bright and achieves an overall detection efficiency of up to 21% per photon. For the first time, a Hong-Ou-Mandel interference with unfiltered photons from separate fibre sources is presented.Comment: 10 pages, 6 figure