Ab-initio Quantum Enhanced Optical Phase Estimation Using Real-time Feedback Control

Optical phase estimation is a vital measurement primitive that is used to perform accurate measurements of various physical quantities like length, velocity and displacements. The precision of such measurements can be largely enhanced by the use of entangled or squeezed states of light as demonstrated in a variety of different optical systems. Most of these accounts however deal with the measurement of a very small shift of an already known phase, which is in stark contrast to ab-initio phase estimation where the initial phase is unknown. Here we report on the realization of a quantum enhanced and fully deterministic phase estimation protocol based on real-time feedback control. Using robust squeezed states of light combined with a real-time Bayesian estimation feedback algorithm, we demonstrate deterministic phase estimation with a precision beyond the quantum shot noise limit. The demonstrated protocol opens up new opportunities for quantum microscopy, quantum metrology and quantum information processing.Comment: 5 figure

Entanglement-enhanced probing of a delicate material system

Quantum metrology uses entanglement and other quantum effects to improve the sensitivity of demanding measurements. Probing of delicate systems demands high sensitivity from limited probe energy and has motivated the field's key benchmark-the standard quantum limit. Here we report the first entanglement-enhanced measurement of a delicate material system. We non-destructively probe an atomic spin ensemble by means of near-resonant Faraday rotation, a measurement that is limited by probe-induced scattering in quantum-memory and spin-squeezing applications. We use narrowband, atom-resonant NOON states to beat the standard quantum limit of sensitivity by more than five standard deviations, both on a per-photon and per-damage basis. This demonstrates quantum enhancement with fully realistic loss and noise, including variable-loss effects. The experiment opens the way to ultra-gentle probing of single atoms, single molecules, quantum gases and living cells.Comment: 7 pages, 8 figures; Nature Photonics, advance online publication, 16 December 201

A comparision of GHG emissions from UK field crop production under selected arable systems with reference to disease control

Crop disease not only threatens global food security by reducing crop production at a time of growing demand, but also contributes to greenhouse gas (GHG) emissions by reducing efficiency of N fertiliser use and farm operations and by driving land use change. GHG emissions associated with adoption of reduced tillage, organic and integrated systems of field crop production across the UK and selected regions are compared with emissions from conventional arable farming to assess their potential for climate change mitigation. The reduced tillage system demonstrated a modest (<20%) reduction in emissions in all cases, although in practice it may not be suitable for all soils and it is likely to cause problems with control of diseases spread on crop debris. There were substantial increases in GHG emissions associated with the organic and integrated systems at national level, principally due to soil organic carbon losses from land use change. At a regional level the integrated system shows the potential to deliver significant emission reductions. These results indicate that the conventional crop production system, coupled to reduced tillage cultivation where appropriate, is generally the best for producing high yields to minimise greenhouse gas emissions and contribute to global food security, although there may be scope for use of the integrated system on a regional basis. The control of crop disease will continue to have an essential role in both maintaining productivity and decreasing GHG emissions.Peer reviewe

GeneXpert—A Game-Changer for Tuberculosis Control?

Carlton Evans considers whether the new tuberculosis diagnostic test, GeneXpert, is the solution for TB control that it's said to be

Effect of terminal accuracy requirements on temporal gaze-hand coordination during fast discrete and reciprocal pointings

Background\ud \ud Rapid discrete goal-directed movements are characterized by a well known coordination pattern between the gaze and the hand displacements. The gaze always starts prior to the hand movement and reaches the target before hand velocity peak. Surprisingly, the effect of the target size on the temporal gaze-hand coordination has not been directly investigated. Moreover, goal-directed movements are often produced in a reciprocal rather than in a discrete manner. The objectives of this work were to assess the effect of the target size on temporal gaze-hand coordination during fast 1) discrete and 2) reciprocal pointings.\ud \ud Methods\ud \ud Subjects performed fast discrete (experiment 1) and reciprocal (experiment 2) pointings with an amplitude of 50 cm and four target diameters (7.6, 3.8, 1.9 and 0.95 cm) leading to indexes of difficulty (ID = log2[2A/D]) of 3.7, 4.7, 5.7 and 6.7 bits. Gaze and hand displacements were synchronously recorded. Temporal gaze-hand coordination parameters were compared between experiments (discrete and reciprocal pointings) and IDs using analyses of variance (ANOVAs).\ud \ud Results\ud \ud Data showed that the magnitude of the gaze-hand lead pattern was much higher for discrete than for reciprocal pointings. Moreover, while it was constant for discrete pointings, it decreased systematically with an increasing ID for reciprocal pointings because of the longer duration of gaze anchoring on target.\ud \ud Conclusion \ud \ud Overall, the temporal gaze-hand coordination analysis revealed that even for high IDs, fast reciprocal pointings could not be considered as a concatenation of discrete units. Moreover, our data clearly illustrate the smooth adaptation of temporal gaze-hand coordination to terminal accuracy requirements during fast reciprocal pointings. It will be interesting for further researches to investigate if the methodology used in the experiment 2 allows assessing the effect of sensori-motor deficits on gaze-hand coordination

Serological Testing Versus Other Strategies for Diagnosis of Active Tuberculosis in India: A Cost-Effectiveness Analysis

This cost-effectiveness study shows that sputum smear microscopy is the most cost-effective test for active tuberculosis (TB) in India, and liquid culture plus microscopy is more cost-effective for TB diagnosis than serological tests

The Impact of Schistosoma japonicum Infection and Treatment on Ultrasound-Detectable Morbidity: A Five-Year Cohort Study in Southwest China

Schistosomiasis is a water-borne parasite that infects approximately 200 million people worldwide. Schistosoma japonicum, found in Asia, causes disease by releasing eggs in the liver, leading to fibrosis, anemia, and, in children, impaired growth. Ultrasound can assess liver pathology from schistosomiasis; however more information is needed to evaluate the relevance of standard ultrasound measures. We followed 578 people for up to five years, testing for schistosomiasis infection and conducting ultrasound examinations to assess the relationship between infection and seven ultrasound measures and to evaluate the impact of treatment with anti-schistosomiasis chemotherapy (praziquantel) on morbidity. All infections were promptly treated. Fibrosis of the liver parenchyma, pathology unique to S. japonicum, was associated with schistosomiasis infection, and was most advanced in people with high worm burdens. Liver fibrosis declined significantly following treatment, but reversal of severe liver fibrosis was rare. Other ultrasound measures were not consistently related to schistosomiasis infection or treatment. These findings suggest parenchymal fibrosis can be used to measure morbidity attributable to S. japonicum and evaluate the impact of disease control efforts. Because reversal of severe fibrosis was limited, disease control efforts will be most effective if they can not only treat existing infections but also prevent new infections

The effect of temperature, gradient and load carriage on oxygen consumption, posture and gait characteristics

Purpose The purpose of this experiment was to evaluate the effect of load carriage in a range of temperatures to establish the interaction between cold exposure, the magnitude of change from unloaded to loaded walking and gradient. Methods Eleven participants (19-27 years) provided written informed consent before performing six randomly ordered walking trials in six temperatures (20°C, 10°C, 5°C, 0°C, -5°C and -10°C). Trials involved two unloaded walking bouts before and after loaded walking (18.2 kg) at 4 km.hr⁻¹, on 0% and 10% gradients in 4 minute bouts. Results The change in absolute oxygen consumption (V̇O₂) from the first unloaded bout to loaded walking was similar across all six temperatures. When repeating the second unloaded bout, V̇O₂ at both -5°C and-10°C was greater compared to the first. At -10°C, V̇O₂ was increased from 1.60 ± 0.30 L.min⁻¹ to 1.89 ± 0.51 L.min⁻¹. Regardless of temperature, gradient had a greater effect on V̇O₂ and heart rate (HR) than backpack load. HR was unaffected by temperature. Stride length (SL) decreased with decreasing temperature but trunk forward lean was greater during cold exposure. Conclusion Decreased ambient temperature did not influence the magnitude of change in V̇O₂ from unloaded to loaded walking. However, in cold temperatures, V̇O₂ was significantly higher than in warm conditions. The increased V̇O₂ in colder temperatures at the same exercise intensity is predicted to ultimately lead to earlier onset of fatigue and cessation of exercise. These results highlight the need to consider both appropriate clothing and fitness during cold exposure

Condensed Mitotic Chromosome Structure at Nanometer Resolution Using PALM and EGFP- Histones

Photoactivated localization microscopy (PALM) and related fluorescent biological imaging methods are capable of providing very high spatial resolutions (up to 20 nm). Two major demands limit its widespread use on biological samples: requirements for photoactivatable/photoconvertible fluorescent molecules, which are sometimes difficult to incorporate, and high background signals from autofluorescence or fluorophores in adjacent focal planes in three-dimensional imaging which reduces PALM resolution significantly. We present here a high-resolution PALM method utilizing conventional EGFP as the photoconvertible fluorophore, improved algorithms to deal with high levels of biological background noise, and apply this to imaging higher order chromatin structure. We found that the emission wavelength of EGFP is efficiently converted from green to red when exposed to blue light in the presence of reduced riboflavin. The photon yield of red-converted EGFP using riboflavin is comparable to other bright photoconvertible fluorescent proteins that allow <20 nm resolution. We further found that image pre-processing using a combination of denoising and deconvolution of the raw PALM images substantially improved the spatial resolution of the reconstruction from noisy images. Performing PALM on Drosophila mitotic chromosomes labeled with H2AvD-EGFP, a histone H2A variant, revealed filamentous components of ∼70 nm. This is the first observation of fine chromatin filaments specific for one histone variant at a resolution approximating that of conventional electron microscope images (10–30 nm). As demonstrated by modeling and experiments on a challenging specimen, the techniques described here facilitate super-resolution fluorescent imaging with common biological samples