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Fernanda V Costa, Marco A R Mello, Judith L Bronstein, Tadeu J Guerra, Renata L Muylaert, Alice C Leite, Frederico S Neves
Ant-plant associations are an outstanding model to study the entangled ecological interactions that structure communities. However, most studies of plant-animal networks focus on only one type of resource that mediates these interactions (e.g, nectar or fruits), leading to a biased understanding of community structure. New approaches, however, have made possible to study several interaction types simultaneously through multilayer networks models. Here, we use this approach to ask whether the structural patterns described to date for ant-plant networks hold when multiple interactions with plant-derived food rewards are considered...
2016: PloS One
Akira Shimizu, Tomoyuki Morimae
This corrects the article DOI: 10.1103/PhysRevLett.95.090401.
November 18, 2016: Physical Review Letters
Lukas Knips, Christian Schwemmer, Nico Klein, Marcin Wieśniak, Harald Weinfurter
Certifying entanglement of a multipartite state is generally considered a demanding task. Since an N qubit state is parametrized by 4^{N}-1 real numbers, one might naively expect that the measurement effort of generic entanglement detection also scales exponentially with N. Here, we introduce a general scheme to construct efficient witnesses requiring a constant number of measurements independent of the number of qubits for states like, e.g., Greenberger-Horne-Zeilinger states, cluster states, and Dicke states...
November 18, 2016: Physical Review Letters
Xi-Lin Wang, Luo-Kan Chen, W Li, H-L Huang, C Liu, C Chen, Y-H Luo, Z-E Su, D Wu, Z-D Li, H Lu, Y Hu, X Jiang, C-Z Peng, L Li, N-L Liu, Yu-Ao Chen, Chao-Yang Lu, Jian-Wei Pan
We report the first experimental demonstration of quantum entanglement among ten spatially separated single photons. A near-optimal entangled photon-pair source was developed with simultaneously a source brightness of ∼12  MHz/W, a collection efficiency of ∼70%, and an indistinguishability of ∼91% between independent photons, which was used for a step-by-step engineering of multiphoton entanglement. Under a pump power of 0.57 W, the ten-photon count rate was increased by about 2 orders of magnitude compared to previous experiments, while maintaining a state fidelity sufficiently high for proving the genuine ten-particle entanglement...
November 18, 2016: Physical Review Letters
Chen Zhang, Wei Li, Yi Hu, Tao Yang, Ge Jin, Xiao Jiang
In this paper, we demonstrate a coincidence counting system with 48 input channels which is aimed to count all coincidence events, up to 531 441 kinds, in a multiphoton experiment. Using the dynamic delay adjusting inside the Field Programmable Gate Array, the alignment of photon signals of 48 channels is achieved. After the alignment, clock phase shifting is used to sample signal pulses. Logic constraints are used to stabilize the pulse width. The coincidence counting data stored in a 1G bit external random access memory will be sent to the computer to analyze the amount of 2-, 3-, 4-, 5-, and 6-fold coincidence events...
November 2016: Review of Scientific Instruments
Yoon-Seok Lee, Sang Min Lee, Heonoh Kim, Han Seb Moon
We report a bright photon-pair source with a coincidence counting rate per input power (cps/mW) of tens of thousands, obtained via spontaneous four-wave mixing from a Doppler-broadened atomic ensemble of the 5S<sub>1/2</sub>-5P<sub>3/2</sub>-5D<sub>5/2</sub> transition of <sup>87</sup>Rb. The photon-pair generation rate is enhanced by the two-photon coherence contributions from almost all the atomic velocity groups in the Doppler-broadened ladder-type atomic system...
November 28, 2016: Optics Express
Zhao-Qin Wu, Hui Cao, Hao-Liang Zhang, Shan-Jun Ma, Jie-Hui Huang
Due to the restrictions on quantum measurement imposed by relativistic causality, it is not easy to perform a nonlocal measurement on spacelike separated systems instantaneously. Here we design an experiment in an optical system to perform the nonlocal measurement of a product observable on a two-qubit system, where a maximally-entangled two-qubit state, acting as an ancillary meter, and three identical Kerr media are used to couple the system under consideration and the target meter. It is shown that the nonlocal measurement of the product observable, σzA⊗σzB, which has two degenerate eigenvalues, could be implemented in a deterministic way without violating relativistic causality...
November 28, 2016: Optics Express
Wen-Jing Chu, Ming Yang, Guo-Zhu Pan, Qing Yang, Zhuo-Liang Cao
An optical scheme for simulating nonlocality distillation is proposed in post-quantum regime. The nonlocal boxes are simulated by measurements on appropriately pre- and post-selected polarization entangled photon pairs, i.e. post-quantum nonlocality is simulated by exploiting fair-sampling loophole in a Bell test. Mod 2 addition on the outputs of two nonlocal boxes combined with pre- and post-selection operations constitutes the key operation of simulating nonlocality distillation. This scheme provides a possible tool for the experimental study on the nonlocality in post-quantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones...
November 28, 2016: Optics Express
Sara Restuccia, Daniel Giovannini, Graham Gibson, Miles Padgett
Using a spontaneous parametric down-conversion process to create entangled spatial states, we compare the information capacity associated with measurements in the Hermite-Gaussian and Laguerre-Gaussian modal basis in an optical system of finite aperture. We show that the cross-talk imposed by the aperture restriction degrades the information capacity. However, the Laguerre-Gaussian mode measurements show greater resilience to cross talk than the Hermite-Gaussian, suggesting that the Laguerre-Gaussian modal set may still offer real-world advantages over other modal sets...
November 28, 2016: Optics Express
Chao Zhang, Yun-Feng Huang, Cheng-Jie Zhang, Jian Wang, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo
High-quality entangled photon pairs generated via spontaneous parametric down-conversion have made great contributions to the modern quantum information science and the fundamental tests of quantum mechanics. However, the quality of the entangled states decreases sharply when moving from biphoton to multiphoton experiments, mainly due to the lack of interactions between photons. Here, for the first time, we generate a four-photon Greenberger-Horne-Zeilinger state with a fidelity of 98%, which is even comparable to the best fidelity of biphoton entangled states...
November 28, 2016: Optics Express
Frank Setzpfandt, Alexander S Solntsev, Andrey A Sukhorukov
In spontaneous parametric downconversion (SPDC), a pump photon spontaneously splits into signal and idler photons in media with quadratic nonlinearity. This phenomenon is the most widely utilized source of entangled photons with multiple applications in quantum information technology. SPDC on a chip is usually treated as a local process, meaning that signal and idler photons are created in the same position at which the pump photon is destroyed. We reveal that this locality condition can be violated in an array of coupled waveguides...
December 1, 2016: Optics Letters
R I Khakimov, B M Henson, D K Shin, S S Hodgman, R G Dall, K G H Baldwin, A G Truscott
Ghost imaging is a counter-intuitive phenomenon-first realized in quantum optics-that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a 'ghost' image...
November 30, 2016: Nature
Björn Lampinen, Filip Szczepankiewicz, Johan Mårtensson, Danielle van Westen, Pia C Sundgren, Markus Nilsson
In diffusion MRI (dMRI), microscopic diffusion anisotropy can be obscured by orientation dispersion. Separation of these properties is of high importance, since it could allow dMRI to non-invasively probe elongated structures such as neurites (axons and dendrites). However, conventional dMRI, based on single diffusion encoding (SDE), entangles microscopic anisotropy and orientation dispersion with intra-voxel variance in isotropic diffusivity. SDE-based methods for estimating microscopic anisotropy, such as the neurite orientation dispersion and density imaging (NODDI) method, must thus rely on model assumptions to disentangle these features...
November 26, 2016: NeuroImage
Meiyu Wang, Fengli Yan, Ting Gao
We propose a theoretical protocol for preparing four-photon polarization entangled decoherence-free states, which are immune to the collective noise. With the assistance of the cross-Kerr nonlinearities, a two-photon spatial entanglement gate, two controlled-NOT gates, a four-photon polarization entanglement gate are inserted into the circuit, where X homodyne measurements are aptly applied. Combined with some swap gates and simple linear optical elements, four-photon polarization entangled decoherence-free states which can be utilized to represent two logical qubits, |0〉L and |1〉L are achieved at the output ports of the circuit...
November 30, 2016: Scientific Reports
Valentina Franco-Trecu, Massimiliano Drago, Helena Katz, Emanuel Machín, Yamandú Marín
Plastic debris in marine environments and its impact on wildlife species is becoming a problem of increasing concern. In pinnipeds, entanglements commonly consist of loops around the neck of non-biodegradable materials from fishing gear or commercial packaging, known as "neck collars". These entanglements can cause injuries, death by suffocation and starvation, and therefore they may add to the overall decrease in population. Our objective was to describe the entanglement of two species of otariids (Arctocephalus australis and Otaria flavescens) in the South West Atlantic Ocean...
November 26, 2016: Environmental Pollution
Po-Hsiang Wang, Shuiquan Tang, Kayla Nemr, Robert Flick, Jun Yan, Radhakrishnan Mahadevan, Alexander F Yakunin, Frank E Löffler, Elizabeth A Edwards
Two novel chlorinated alkane-respiring Dehalobacter restrictus strains CF and DCA were isolated from the same enrichment culture, ACT-3, and characterized. The closed genomes of these highly similar sister strains were previously assembled from metagenomic sequence data and annotated. The isolation of the strains enabled experimental verification of predicted annotations, particularly focusing on irregularities or predicted gaps in central metabolic pathways and cofactor biosynthesis. Similar to D. restrictus strain PER-K23, strains CF and DCA require arginine, histidine and threonine for growth, although the corresponding biosynthesis pathways are predicted to be functional...
November 29, 2016: ISME Journal
P Chen, Y-H Chan, X-Y Fang, S-K Mo, Z Hussain, A-V Fedorov, M Y Chou, T-C Chiang
Charge density wave (CDW) formation, a key physics issue for materials, arises from interactions among electrons and phonons that can also lead to superconductivity and other competing or entangled phases. The prototypical system TiSe2, with a particularly simple (2 × 2 × 2) transition and no Kohn anomalies caused by electron-phonon coupling, is a fascinating but unsolved case after decades of research. Our angle-resolved photoemission measurements of the band structure as a function of temperature, aided by first-principles calculations, reveal a hitherto undetected but crucial feature: a (2 × 2) electronic order in each layer sets in at ~232 K before the widely recognized three-dimensional structural order at ~205 K...
November 29, 2016: Scientific Reports
Subhayan Roy Moulick, Prasanta K Panigrahi
We study the nature of entanglement in presence of Deutschian closed timelike curves (D-CTCs) and open timelike curves (OTCs) and find that existence of such physical systems in nature would allow us to increase entanglement using local operations and classical communication (LOCC). This is otherwise in direct contradiction with the fundamental definition of entanglement. We study this problem from the perspective of Bell state discrimination, and show how D-CTCs and OTCs can unambiguously distinguish between four Bell states with LOCC, that is otherwise known to be impossible...
November 29, 2016: Scientific Reports
Antonio Lazcano
The heterotrophic origin of life proposed by A. I. Oparin in the 1920s was part of a Darwinian framework that assumed that living organisms were the historical outcome of a gradual transformation of lifeless matter. Eighty years ago, he presented a much more detailed scheme of the processes that may have led to life. As argued here, the development of the heterotrophic theory has been shaped by an entangled scenario in which a number of technical and scientific developments concur, as well as non-scientific issues including the Stalinist period and the tensions of the Cold War atmosphere...
November 28, 2016: Journal of Molecular Evolution
Zhong-Xiao Wang, Shuhao Wang, Teng Ma, Tie-Jun Wang, Chuan Wang
The generation and quantification of quantum entanglement is crucial for quantum information processing. Here we study the transition of Gaussian correlation under the effect of linear optical beam-splitters. We find the single-mode Gaussian coherence acts as the resource in generating Gaussian entanglement for two squeezed states as the input states. With the help of consecutive beam-splitters, single-mode coherence and quantum entanglement can be converted to each other. Our results reveal that by using finite number of beam-splitters, it is possible to extract all the entanglement from the single-mode coherence even if the entanglement is wiped out before each beam-splitter...
November 28, 2016: Scientific Reports
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