58 research outputs found
Observation of eight-photon entanglement
Using ultra-bright sources of pure-state entangled photons from parametric
down conversion, an eight-photon interferometer and post-selection detection,
we demonstrate the ability to experimentally manipulate eight individual
photons and report the creation of an eight-photon Schr\"odinger cat state with
an observed fidelity of .Comment: 6 pages, 4 figure
Biphoton generation in quadratic waveguide arrays: A classical optical simulation
Quantum entanglement, the non-separability of a multipartite wave function,
became essential in understanding the non-locality of quantum mechanics. In
optics, this non-locality can be demonstrated on impressively large length
scales, as photons travel with the speed of light and interact only weakly with
their environment. With the discovery of spontaneous parametric down-conversion
(SPDC) in nonlinear crystals, an efficient source for entangled photon pairs,
so-called biphotons, became available. It has recently been shown that SPDC can
also be implemented in nonlinear arrays of evanescently coupled waveguides
which allows the generation and the investigation of correlated quantum walks
of such biphotons in an integrated device. Here, we analytically and
experimentally demonstrate that the biphoton degrees of freedom are entailed in
an additional spatial dimension, therefore the SPDC and the subsequent quantum
random walk in one-dimensional (1D) arrays can be simulated through classical
optical beam propagation in a two-dimensional (2D) photonic lattice. Thereby,
the output intensity images directly represent the biphoton correlations and
exhibit a clear violation of a Bell-type inequality
Haplotype Analysis Reveals a Possible Founder Effect of RET Mutation R114H for Hirschsprung's Disease in the Chinese Population
Background Hirschsprung's disease (HSCR) is a congenital disorder associated with the lack of intramural ganglion cells in the myenteric and sub-mucosal plexuses along varying segments of the gastrointestinal tract. The RET gene is the major gene implicated in this gastrointestinal disease. A highly recurrent mutation in RET (RETR114H) has recently been identified in ~6-7% of the Chinese HSCR patients which, to date, has not been found in Caucasian patients or controls nor in Chinese controls. Due to the high frequency of RETR114H in this population, we sought to investigate whether this mutation may be a founder HSCR mutation in the Chinese population. Methodology and Principal Findings To test whether all RETR114H were originated from a single mutational event, we predicted the approximate age of RETR114H by applying a Bayesian method to RET SNPs genotyped in 430 Chinese HSCR patients (of whom 25 individuals had the mutation) to be between 4-23 generations old depending on growth rate. We reasoned that if RETR114H was a founder mutation then those with the mutation would share a haplotype on which the mutation resides. Including SNPs spanning 509.31 kb across RET from a recently obtained 500 K genome-wide dataset for a subset of 181 patients (14 RETR114H patients), we applied haplotype estimation methods to determine whether there were any segments shared between patients with RETR114H that are not present in those without the mutation or controls. Analysis yielded a 250.2 kb (51 SNP) shared segment over the RET gene (and downstream) in only those patients with the mutation with no similar segments found among other patients. Conclusions This suggests that RETR114H is a founder mutation for HSCR in the Chinese population. © 2010 Cornes et al.published_or_final_versio
Retweeting: its linguistic and epistemic value
This paper analyses the communicative and epistemic value of retweeting (and more generally of reposting content on social media). Against a naïve view, it argues that retweets are not acts of endorsement, motivating this diagnosis with linguistic data. Retweeting is instead modelled as a peculiar form of quotation, in which the reported content is indicated rather than reproduced. A relevance-theoretic account of the communicative import of retweeting is then developed, to spell out the complex mechanisms by which retweets achieve their communicative goals. The last section outlines the epistemic threats posed by the increasing prevalence of retweeting on social media, linking them to the low reputational, cognitive, and practical costs linked to this emerging form of communication
Quantum interference with distinguishable photons through indistinguishable pathways
We report a two-photon quantum interference experiment in which the detected individual photons have quite different properties. The interference is observed even when no effort is made to mask the distinguishing features before the photons are detected. The results can be explained only in terms of indistinguishable two-photon amplitudes. (C) 2005 Optical Society of America.X1117sciescopu
Measurement of the spectral properties of the two-photon state generated via type II spontaneous parametric downconversion
We report complete measurement of the spectral properties of photon pairs generated via spontaneous parametric downconversion. The measurements, which include not only single-photon spectra but also two-photon joint spectra, were performed for both cw and ultrafast-pumping configurations. In agreement with theoretical predictions, the spectra for the ultrafast-pumped case reveal asymmetries that are not present with cw pumping. (c) 2005 Optical Society of America.X1165sciescopu
Photon Bunching and Multi-photon Interference between Independent Parametric Down-Conversion Processes
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