Weak values and the Leggett-Garg inequality in solid-state qubits

An implementation of weak values is investigated in solid-state qubits. We demonstrate that a weak value can be non-classical if and only if a Leggett-Garg inequality can also be violated. Generalized weak values are described, where post-selection on a range of weak measurement results. Imposing classical weak values permits the derivation of Leggett-Garg inequalities for bounded operators. Our analysis is presented in terms of kicked quantum nondemolition measurements on a quantum double-dot charge qubit.Comment: 4 pages, 2 figure

Bounds on Quantum Correlations in Bell Inequality Experiments

Bell inequality violation is one of the most widely known manifestations of entanglement in quantum mechanics; indicating that experiments on physically separated quantum mechanical systems cannot be given a local realistic description. However, despite the importance of Bell inequalities, it is not known in general how to determine whether a given entangled state will violate a Bell inequality. This is because one can choose to make many different measurements on a quantum system to test any given Bell inequality and the optimization over measurements is a high-dimensional variational problem. In order to better understand this problem we present algorithms that provide, for a given quantum state, both a lower bound and an upper bound on the maximal expectation value of a Bell operator. Both bounds apply techniques from convex optimization and the methodology for creating upper bounds allows them to be systematically improved. In many cases these bounds determine measurements that would demonstrate violation of the Bell inequality or provide a bound that rules out the possibility of a violation. Examples are given to illustrate how these algorithms can be used to conclude definitively if some quantum states violate a given Bell inequality.Comment: 13 pages, 1 table, 2 figures. Updated version as published in PR

Early CRT monitoring using time-domain optical coherence tomography does not add to visual acuity for predicting visual loss in patients with central retinal vein occlusion treated with intravitreal ranibizumab:A secondary analysis of trial data

Our primary purpose was to assess the clinical (predictive) validity of central retinal thickness (CRT) and best corrected visual acuity (BCVA) at 1 week and 1 month after starting treatment with ranibizumab for central retinal vein occlusion. The authors also assessed detectability of response to treatment

A temporal waterline approach to mapping intertidal areas using X-band marine radar

Mapping the morphology of intertidal areas is a logistically challenging, time consuming and expensive task due to their large expanse and difficulties associated with access. A technique is presented here that uses standard marine navigational radar operating at X-band frequency. The method uses a series of time-exposure radar images over the course of a two-week tidal cycle to identify the elevation of the wetting and drying transitions at each pixel in the radar images, thereby building up a morphological map of the target intertidal area. This “Temporal Waterline” method is applied to a dataset acquired from Hilbre Island at the mouth of the Dee Estuary, UK, spanning March 2006 to January 2007. The radar gathered data with a radial range of 4 km and the resulting elevation maps describe the intertidal regions of that area. The results are compared with airborne LiDAR data surveyed over the same area and within the radar survey time period. The residual differences show good agreement across large areas of beach and sandbanks, with concentrations of poor estimations around points that are shadowed from the radar or likely to suffer from pooling water. This paper presents the theoretical framework of the method and demonstrates its stability and accuracy. The Temporal Waterline radar method is aimed at providing a useful tool for the monitoring and operational management of coastlines

Competitive release of drug resistance following drug treatment of mixed Plasmodium chabaudi infections

BACKGROUND: Malaria infections are often genetically diverse, potentially leading to competition between co-infecting strains. Such competition is of key importance in the spread of drug resistance. METHODS: The effects of drug treatment on within-host competition were studied using the rodent malaria Plasmodium chabaudi. Mice were infected simultaneously with a drug-resistant and a drug-sensitive clone and were then either drug-treated or left untreated. Transmission was assessed by feeding mice to Anopheles stephensi mosquitoes. RESULTS: In the absence of drugs, the sensitive clone competitively suppressed the resistant clone; this resulted in lower asexual parasite densities and also reduced transmission to the mosquito vector. Drug treatment, however, allowed the resistant clone to fill the ecological space emptied by the removal of the sensitive clone, allowing it to transmit as well as it would have done in the absence of competition. CONCLUSION: These results show that under drug pressure, resistant strains can have two advantages: (1) they survive better than sensitive strains and (2) they can exploit the opportunities presented by the removal of their competitors. When mixed infections are common, such effects could increase the spread of drug resistance

Better Bell Inequality Violation by Collective Measurements

The standard Bell inequality experiments test for violation of local realism by repeatedly making local measurements on individual copies of an entangled quantum state. Here we investigate the possibility of increasing the violation of a Bell inequality by making collective measurements. We show that nonlocality of bipartite pure entangled states, quantified by their maximal violation of the Bell-Clauser-Horne inequality, can always be enhanced by collective measurements, even without communication between the parties. For mixed states we also show that collective measurements can increase the violation of Bell inequalities, although numerical evidence suggests that the phenomenon is not common as it is for pure states.Comment: 7 pages, 4 figures and 1 table; references update

Uplift and Seismicity driven by Magmatic Inflation at Sierra Negra Volcano, Galápagos Islands

Catalogue of detected earthquakes and cGPS uplift timeseries for Sierra Negra Volcano, Galapagos Island

Online tools for assessing the climatology and predictability of rainfall and temperature in the Indo-Gangetic plains based on observed datasets and seasonal forecast models

Rainfall in the Northern India-Nepal-Bangladesh region is crucial for farmers, water managers and others in the region. Most precipitation falls predominantly during the south Asian summer monsoon season. The phase of El Niño-Southern Oscillation (ENSO) affects the monsoon as well as winter rainfall in some of the region, but the spring predictability barrier and weakness of ENSO-monsoon relationships lead to relatively low-to-moderate seasonal forecast skill in the region during summer. This report documents a set of tools developed to facilitate the analysis of the mean climate and the predictability of seasonal climate in the region and presents preliminary results for the summer monsoon season. These tools advance the tailoring of historical and forecast climate information for agriculture and increase the accessibility of the information via online map rooms to benefit stakeholders throughout the region