Efficient photon number detection with silicon avalanche photodiodes

We demonstrate an efficient photon number detector for visible wavelengths using a silicon avalanche photodiode. Under subnanosecond gating, the device is able to resolve up to four photons in an incident optical pulse. The detection efficiency at 600 nm is measured to be 73.8%, corresponding to an avalanche probability of 91.1% of the absorbed photons, with a dark count probability below 1.1x10^{-6} per gate. With this performance and operation close to room temperature, fast-gated silicon avalanche photodiodes are ideal for optical quantum information processing that requires single-shot photon number detection

Impact of ICARDA Research on Australian Agriculture

Research and Development/Tech Change/Emerging Technologies,

Probing higher order correlations of the photon field with photon number resolving avalanche photodiodes

We demonstrate the use of two high speed avalanche photodiodes in exploring higher order photon correlations. By employing the photon number resolving capability of the photodiodes the response to higher order photon coincidences can be measured. As an example we show experimentally the sensitivity to higher order correlations for three types of photon sources with distinct photon statistics. This higher order correlation technique could be used as a low cost and compact tool for quantifying the degree of correlation of photon sources employed in quantum information science

Determination of the strange nucleon form factors

The strange contribution to the electric and magnetic form factors of the nucleon is determined at a range of discrete values of $Q^2$ up to $1.4$ GeV$^2$. This is done by combining recent lattice QCD results for the electromagnetic form factors of the octet baryons with experimental determinations of those quantities. The most precise result is a small negative value for the strange magnetic moment: $G_M^s(Q^2=0) = -0.07\pm0.03\,\mu_N$. At larger values of $Q^2$ both the electric and magnetic form factors are consistent with zero to within $2$-sigma

Charge Symmetry Violation in the Electromagnetic Form Factors of the Proton

Experimental tests of QCD through its predictions for the strange-quark content of the proton have been drastically restricted by our lack of knowledge of the violation of charge symmetry (CSV). We find unexpectedly tiny CSV in the proton's electromagnetic form factors by performing the first extraction of these quantities based on an analysis of lattice QCD data. The resulting values are an order of magnitude smaller than current bounds on proton strangeness from parity violating electron-proton scattering experiments. This result paves the way for a new generation of experimental measurements of the proton's strange form factors to challenge the predictions of QCD

Multi-Objective Big Data Optimization with jMetal and Spark

Big Data Optimization is the term used to refer to optimization problems which have to manage very large amounts of data. In this paper, we focus on the parallelization of metaheuristics with the Apache Spark cluster computing system for solving multi-objective Big Data Optimization problems. Our purpose is to study the influence of accessing data stored in the Hadoop File System (HDFS) in each evaluation step of a metaheuristic and to provide a software tool to solve these kinds of problems. This tool combines the jMetal multi-objective optimization framework with Apache Spark. We have carried out experiments to measure the performance of the proposed parallel infrastructure in an environment based on virtual machines in a local cluster comprising up to 100 cores. We obtained interesting results for computational e ort and propose guidelines to face multi-objective Big Data Optimization problems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Investigation of poly(2-methoxy-5-(2 '-ethylhexyloxy)-1,4-phenylenevinylene) prepared via a chloro precursor route

We report the characterisation of an insoluble MEHPPV (I-MEHPPV) prepared via a chloro precursor route. Optical absorption and emission spectra are discussed with reference to those of the common soluble variant. PL quantum efficiencies are also reported. Results obtained for single ITO/I-MEHPPV/A1 and double layer ITO/I-MEHPPV/electron transport layer (ETL)/A1 LED structures are discussed. Peak luminances of 800cd/m(2) are found for the multilayer device and a peak EL external quantum efficiency of 0.1 1% (power conversion efficiency of 1.5x10(-5)W/W) is obtained

Releasing The Anti-inflammatory Potential of Paralysed Skeletal Muscle: The Circulating Cytokine Response to Voluntary Upper-limb Exercise With/Without The Addition of Functional Electrical Stimulation (FES)-evoked Lower-limb Contractions

Skeletal muscle is a rich store of inflammatory mediating ‘myokines’. Following release from contracting muscle, the myokine interleukin-6 (IL-6) promotes a circulating anti-inflammatory environment associated with a reduced risk of cardiovascular disease (CVD). The metabolic and functional consequences of lower-limb paralysis, including the gain in relative adiposity and physical inactivity, result in a high prevalence of CVD in individuals with a spinal cord injury (SCI). However, the magnitude of any contraction-induced myokine response in this population may be limited by the small active muscle mass of the upper-limb. The combination of voluntary, upper-limb exercise and involuntary, functional electrical stimulation (FES)-evoked lower-limb cycling termed ‘hybrid’ exercise, may augment the acute myokine response by activating a greater volume of muscle mass than upper-limb exercise alone. Five community-based individuals with motor complete, thoracic SCI (Age=44±15 years; Body mass=66.6±14.3 kg) and at least 3 months FES-evoked cycling experience volunteered to participate. On separate occasions, each participant performed 30 min of voluntary upper-limb, hand cycling exercise with (HYBRID) and without (ARM only) the addition of FES-evoked lower-limb cycling at a fixed workload. Blood samples were collected at rest, immediately post-exercise, and 1 and 2 h post-exercise. Plasma concentrations of IL-6, IL-10 and IL-1ra were subsequently determined by enzyme linked immunoassay. Estimated energy expenditure was significantly higher in HYBRID (154±25 kcal) than ARM (132±21 kcal) (P=0.01; ES=0.90). Plasma IL-6 concentrations were significantly elevated following HYBRID, with values 1 h and 2 h post-exercise significantly higher than rest and immediately post-exercise (P\u3c0.04). A small (~50%) non-significant increase in IL-6 was present 1 h and 2 h post-exercise following ARM, however concentrations were significantly higher in HYBRID than ARM at the same time points (P\u3c0.02). Plasma IL-10 concentrations were unaffected by exercise in ARM. Although not attaining statistical significance, there was a tendency for IL-10 concentrations to rise in HYBRID, with an 85% increase in IL-10 concentrations at 2 h post exercise. Plasma IL-1ra was unaffected by exercise in both trials. Initial findings suggest paralysed skeletal muscle releases the myokine IL-6 in response to electrically evoked contractions. Further, voluntary upper-limb exercise combined with involuntary lower-limb FES-evoked exercise had the tendency to elevate plasma concentrations of the anti-inflammatory cytokine IL-10; this effect was not present when performing arm exercise alone. Hybrid exercise may offer a method of maximising the anti-inflammatory potential of acute exercise in individuals with a SCI. The current findings require verification in a larger cohort

Iron Age and Anglo-Saxon genomes from East England reveal British migration history

British population history has been shaped by a series of immigrations, including the early Anglo-Saxon migrations after 400 CE. It remains an open question how these events affected the genetic composition of the current British population. Here, we present whole-genome sequences from 10 individuals excavated close to Cambridge in the East of England, ranging from the late Iron Age to the middle Anglo-Saxon period. By analysing shared rare variants with hundreds of modern samples from Britain and Europe, we estimate that on average the contemporary East English population derives 38% of its ancestry from Anglo-Saxon migrations. We gain further insight with a new method, rarecoal, which infers population history and identifies fine-scale genetic ancestry from rare variants. Using rarecoal we find that the Anglo-Saxon samples are closely related to modern Dutch and Danish populations, while the Iron Age samples share ancestors with multiple Northern European populations including Britain

Quantum Tricritical Points in NbFe2_2

Quantum critical points (QCPs) emerge when a 2nd order phase transition is suppressed to zero temperature. In metals the quantum fluctuations at such a QCP can give rise to new phases including unconventional superconductivity. Whereas antiferromagnetic QCPs have been studied in considerable detail ferromagnetic (FM) QCPs are much harder to access. In almost all metals FM QCPs are avoided through either a change to 1st order transitions or through an intervening spin-density-wave (SDW) phase. Here, we study the prototype of the second case, NbFe$_2$. We demonstrate that the phase diagram can be modelled using a two-order-parameter theory in which the putative FM QCP is buried within a SDW phase. We establish the presence of quantum tricritical points (QTCPs) at which both the uniform and finite $q$ susceptibility diverge. The universal nature of our model suggests that such QTCPs arise naturally from the interplay between SDW and FM order and exist generally near a buried FM QCP of this type. Our results promote NbFe$_2$ as the first example of a QTCP, which has been proposed as a key concept in a range of narrow-band metals, including the prominent heavy-fermion compound YbRh$_2$Si$_2$.Comment: 21 pages including S