Experimental Ten-Photon Entanglement.

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. Our work created a state-of-the-art platform for multiphoton experiments, and enabled technologies for challenging optical quantum information tasks, such as the realization of Shor's error correction code and high-efficiency scattershot boson sampling.

[Effect of Rab11 gene expression on the invasion and migration of cervical cancer cell line SiHa in hypoxia].

Objective: To explore the expression of Ras-related protein 11 (Rab11) in hypoxia, the effect of Rab11 on the invasion and migration of cervical cancer cell line SiHa and its possible mechanism. Methods: SiHa cells were divided into 4 groups, the normoxic blank group (normal culture in normoxia), the hypoxic blank group (normal culture in hypoxia), the negative control group [transfection of negative control small interfering RNA (siRNA) in hypoxia], the Rab11-siRNA group (transfection of Rab11 siRNA in hypoxia). Western blot was used to examine the expression of Rab11, integrin α5, integrin ß3, phosphorylated focal adhesion kinase (p-FAK), phosphorylated phosphatidylinositol 3 kinase (p-PI3K) protein, together with the expression of Ras correlative C3 creotoxin substrate 1 (Rac1), which was critical in regulating cell invasion. The mRNA expression of Rab11 in the 4 groups was detected by realtime-qPCR. The cell invasion was detected by matrigel assay, while the cell migration was detected by transwell assay. Immunofluorescence was used to identify intracellular location of Rac1 in SiHa cell. Results: (1) The expression of Rab11, intergrin α5, intergrin ß3, p-FAK, p-PI3K and Rac1 in the normoxic blank group were 0.56±0.04, 0.33±0.03, 0.32±0.03, 0.36±0.03, 0.35±0.03 and 0.47±0.03, respectively. In the hypoxic blank group, they were 0.73±0.03, 0.74±0.03, 0.61±0.03, 0.62±0.03, 0.60±0.03 and 0.73±0.03, respectively. In the negative control group, their expressions were 0.72±0.03, 0.73±0.03, 0.59±0.03, 0.61±0.03, 0.59±0.03 and 0.72±0.03, respectively. While in the Rab11-siRNA group, they were 0.44±0.03, 0.30±0.03, 0.29±0.03, 0.30±0.03, 0.30±0.03 and 0.34±0.04, respectively. The expressions of Rab11, α5, ß3, p-FAK, p-PI3K and Rac1 were significantly higher in the hypoxic blank group than in the normoxic blank group (P<0.05), and were significantly lower in the Rab11-siRNA group than in the hypoxic blank group and the negative control group (P<0.05). (2) The expressions of Rab11-mRNA were 1.000±0.000, 1.454±0.114, 1.442±0.101, 0.570± 0.046 in the normoxic blank group, the hypoxic blank group, the negative control group and the Rab11-siRNA group, respectively. It was significantly higher in the hypoxic blank group than in the normoxic blank group (P<0.05), and was significantly lower in the Rab11-siRNA group than in the hypoxic blank group and the negative control group (P<0.05). (3) By Matrigel, the invasion cell number in the normoxic blank group, the hypoxic blank group,the negative control group and the Rab11-siRNA group were 65±12, 106±16, 104± 17 and 50±11, respectively. The invasion capacity was significantly higher in the hypoxic blank group than in the normoxic blank group (P<0.05), and was significantly lower in the Rab11-siRNA group than in the hypoxic blank group and the negative control group (P<0.05). (4) By transwell assay, the migration cells in the normoxic blank group, the hypoxic blank group, the negative control group and the Rab11-siRNA group were 127±12, 169±15, 161±13 and 77±13, respectively. The capacity of invasion was significantly higher in the hypoxic blank group than in the normoxic blank group (P<0.05), and was significantly lower in the Rab11-siRNA group than in the hypoxic blank group and the negative control group (P<0.05). (5) The immunofluorescence showed that the red fluorescence intensity around nucleus was significantly increased in the normoxic blank group, the hypoxic blank group and the negative control group than in the Rab11-siRNA group. Conclusions: Hypoxia could promote the invasion and migration of SiHa cells. In hypoxia, the down regulation of Rab11 expression could inhibit the invasion and migration of SiHa cells. This might be due to the decreased expression of the intergrin α5, intergrin ß3, p-FAK, p-PI3K and Rac1 protein.

Entanglement-based machine learning on a quantum computer.

Machine learning, a branch of artificial intelligence, learns from previous experience to optimize performance, which is ubiquitous in various fields such as computer sciences, financial analysis, robotics, and bioinformatics. A challenge is that machine learning with the rapidly growing "big data" could become intractable for classical computers. Recently, quantum machine learning algorithms [Lloyd, Mohseni, and Rebentrost, arXiv.1307.0411] were proposed which could offer an exponential speedup over classical algorithms. Here, we report the first experimental entanglement-based classification of two-, four-, and eight-dimensional vectors to different clusters using a small-scale photonic quantum computer, which are then used to implement supervised and unsupervised machine learning. The results demonstrate the working principle of using quantum computers to manipulate and classify high-dimensional vectors, the core mathematical routine in machine learning. The method can, in principle, be scaled to larger numbers of qubits, and may provide a new route to accelerate machine learning.

The E. coli monothiol glutaredoxin GrxD forms homodimeric and heterodimeric FeS cluster containing complexes.

Monothiol glutaredoxins (mono-Grx) represent a highly evolutionarily conserved class of proteins present in organisms ranging from prokaryotes to humans. Mono-Grxs have been implicated in iron sulfur (FeS) cluster biosynthesis as potential scaffold proteins and in iron homeostasis via an FeS-containing complex with Fra2p (homologue of E. coli BolA) in yeast and are linked to signal transduction in mammalian systems. However, the function of the mono-Grx in prokaryotes and the nature of an interaction with BolA-like proteins have not been established. Recent genome-wide screens for E. coli genetic interactions reported the synthetic lethality (combination of mutations leading to cell death; mutation of only one of these genes does not) of a grxD mutation when combined with strains defective in FeS cluster biosynthesis (isc operon) functions [Butland, G., et al. (2008) Nature Methods 5, 789-795]. These data connected the only E. coli mono-Grx, GrxD to a potential role in FeS cluster biosynthesis. We investigated GrxD to uncover the molecular basis of this synthetic lethality and observed that GrxD can form FeS-bound homodimeric and BolA containing heterodimeric complexes. These complexes display substantially different spectroscopic and functional properties, including the ability to act as scaffold proteins for intact FeS cluster transfer to the model [2Fe-2S] acceptor protein E. coli apo-ferredoxin (Fdx), with the homodimer being significantly more efficient. In this work, we functionally dissect the potential cellular roles of GrxD as a component of both homodimeric and heterodimeric complexes to ultimately uncover if either of these complexes performs functions linked to FeS cluster biosynthesis.

Movements and stepwise fusion of endodermal precursor cells in leech.

At the four-cell stage, embryos of glossiphoniid leeches comprise identified blastomeres A, B, C and D. Subsequent cleavages of the A, B and C quadrants yield three large, yolk-rich endodermal precursor cells, macromeres A"', B"' and C"'. Eventually, these cells generate the epithelial lining of the gut via cellularization of a multinucleate syncytium. Meanwhile, cleavage in the D quadrant generates ten teloblasts that give rise to segmental mesoderm and ectoderm via stem cell divisions. Here we show that, during cleavage, macromeres A"', B"' and C"' shift clockwise relative to the D quadrant, while C"' comes to envelop the nascent teloblasts. During gastrulation, derivatives of the teloblasts undergo epibolic movements over the surface of the A"', B"' and C"' macromeres to form the germinal plate, from which segmental tissues arise. We find that the three macromeres fuse in a stepwise manner to initiate formation of the multinucleate syncytium; cell C"' fuses about 25 h after the fusion of A"' and B"', and the teloblasts fuse with the macromere-derived syncytium later still. When macromeres are biochemically arrested by microinjecting them with the A chain of ricin, a further difference among the macromeres is revealed. Biochemical arrest of A"' or B"' slightly retards the rate of germinal plate formation, but arrest of C"' frequently accelerates this process.