A fiber-integrated quantum memory for telecom light

We demonstrate the storage and on-demand retrieval of single-photon-level telecom pulses in a fiber cavity. The cavity is formed by fiber Bragg gratings at either end of a single-mode fiber. Photons are mapped into, and out of, the cavity using quantum frequency conversion driven by intense control pulses. In a first, spliced-fiber, cavity we demonstrate storage up to 0.55$\mu$s (11 cavity round trips), with $11.3 \pm 0.1$% total memory efficiency, and a signal-to-noise ratio of $12.8$ after 1 round trip. In a second, monolithic cavity, we increase this lifetime to 1.75$\mu$s (35 round trips) with a memory efficiency of $12.7 \pm 0.2$ (SNR of $7.0 \pm 0.2$) after 1 round trip. Fiber-based cavities for quantum storage at telecom wavelengths offer a promising route to synchronizing spontaneous photon generation events and building scalable quantum networks.Comment: 8 pages, 7 figure

Characterization and functional analysis of seven flagellin genes in Rhizobium leguminosarum bv. viciae. Characterization of R. leguminosarum flagellins

<p>Abstract</p> <p>Background</p> <p><it>Rhizobium leguminosarum </it>bv. <it>viciae </it>establishes symbiotic nitrogen fixing partnerships with plant species belonging to the Tribe Vicieae, which includes the genera <it>Vicia, Lathyrus, Pisum </it>and <it>Lens</it>. Motility and chemotaxis are important in the ecology of <it>R. leguminosarum </it>to provide a competitive advantage during the early steps of nodulation, but the mechanisms of motility and flagellar assembly remain poorly studied. This paper addresses the role of the seven flagellin genes in producing a functional flagellum.</p> <p>Results</p> <p><it>R. leguminosarum </it>strains 3841 and VF39SM have seven flagellin genes (<it>flaA</it>, <it>flaB, flaC, flaD, flaE, flaH</it>, and <it>flaG</it>), which are transcribed separately. The predicted flagellins of 3841 are highly similar or identical to the corresponding flagellins in VF39SM. <it>flaA, flaB, flaC</it>, and <it>flaD </it>are in tandem array and are located in the main flagellar gene cluster. <it>flaH </it>and <it>flaG </it>are located outside of the flagellar/motility region while <it>flaE </it>is plasmid-borne. Five flagellin subunits (FlaA, FlaB, FlaC, FlaE, and FlaG) are highly similar to each other, whereas FlaD and FlaH are more distantly related. All flagellins exhibit conserved amino acid residues at the N- and C-terminal ends and are variable in the central regions. Strain 3841 has 1-3 plain subpolar flagella while strain VF39SM exhibits 4-7 plain peritrichous flagella. Three flagellins (FlaA/B/C) and five flagellins (FlaA/B/C/E/G) were detected by mass spectrometry in the flagellar filaments of strains 3841 and VF39SM, respectively. Mutation of <it>flaA </it>resulted in non-motile VF39SM and extremely reduced motility in 3841. Individual mutations of <it>flaB </it>and <it>flaC </it>resulted in shorter flagellar filaments and consequently reduced swimming and swarming motility for both strains. Mutant VF39SM strains carrying individual mutations in <it>flaD, flaE, flaH</it>, and <it>flaG </it>were not significantly affected in motility and filament morphology. The flagellar filament and the motility of 3841 strains with mutations in <it>flaD </it>and <it>flaG </it>were not significantly affected while <it>flaE </it>and <it>flaH </it>mutants exhibited shortened filaments and reduced swimming motility.</p> <p>Conclusion</p> <p>The results obtained from this study demonstrate that FlaA, FlaB, and FlaC are major components of the flagellar filament while FlaD and FlaG are minor components for <it>R. leguminosarum </it>strains 3841 and VF39SM. We also observed differences between the two strains, wherein FlaE and FlaH appear to be minor components of the flagellar filaments in VF39SM but these flagellin subunits may play more important roles in 3841. This paper also demonstrates that the flagellins of 3841 and VF39SM are possibly glycosylated.</p

Deriving a Generic Energy Consumption Model for Network Enabled Devices

Abstract-Energy saving has become a global issue when people use network enabled equipment in the office or at home. However few methods exist to measure and monitor energy use per user or per application, or to control equipment power states. We propose a generic energy consumption model that is based on the power state of network attached equipment, and that supports power management capabilities. This includes measures for each power state (on/off/sleep) and for per bit energy consumption, per interface, per application and at the network QoS (Quality of Services) level. Given the power state of a network device, a network manger could remotely inspect the energy consumption and make changes to the power management setting; for this to happen we introduce a new MIB (Management Information Base) schema to capture the attributes of relevance. Using an agent based modeling framework, we introduce the overall autonomic architecture that makes it possible to minimize energy consumption of network enabled equipment

Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226-1408 nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300 nm we measure a heralded g(2)(0)=0.25(6) for converted light from an input with g(2)(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.</p

Ultratunable quantum frequency conversion in photonic crystal fiber

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226 - 1408 nm) range in a group-velocity-symmetric photonic crystal fiber (PCF), covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 nm to 1300 nm we measure a heralded $g^{(2)}(0) = 0.25(6)$ for converted light from an input with $g^{(2)}(0) = 0.034(8)$. We expect that this PCF can be used for a myriad of quantum networking tasks

Divergent evolution of terrestrial locomotor abilities in extant Crocodylia

Extant Crocodylia are exceptional because they employ almost the full range of quadrupedal footfall patterns (“gaits”) used by mammals; including asymmetrical gaits such as galloping and bounding. Perhaps this capacity evolved in stem Crocodylomorpha, during the Triassic when taxa were smaller, terrestrial, and long-legged. However, confusion about which Crocodylia use asymmetrical gaits and why persists, impeding reconstructions of locomotor evolution. Our experimental gait analysis of locomotor kinematics across 42 individuals from 15 species of Crocodylia obtained 184 data points for a wide velocity range (0.15–4.35 ms−1). Our results suggest either that asymmetrical gaits are ancestral for Crocodylia and lost in the alligator lineage, or that asymmetrical gaits evolved within Crocodylia at the base of the crocodile line. Regardless, we recorded usage of asymmetrical gaits in 7 species of Crocodyloidea (crocodiles); including novel documentation of these behaviours in 5 species (3 critically endangered). Larger Crocodylia use relatively less extreme gait kinematics consistent with steeply decreasing athletic ability with size. We found differences between asymmetrical and symmetrical gaits in Crocodylia: asymmetrical gaits involved greater size-normalized stride frequencies and smaller duty factors (relative ground contact times), consistent with increased mechanical demands. Remarkably, these gaits did not differ in maximal velocities obtained: whether in Alligatoroidea or Crocodyloidea, trotting or bounding achieved similar velocities, revealing that the alligator lineage is capable of hitherto unappreciated extreme locomotor performance despite a lack of asymmetrical gait usage. Hence asymmetrical gaits have benefits other than velocity capacity that explain their prevalence in Crocodyloidea and absence in Alligatoroidea—and their broader evolution