5,132 research outputs found
An Economic Evaluation of Research into the Improved Management of the Annual Grass Weed Vulpia in Temperate Pastures in South-Eastern Australia
NSW Agriculture has a history of research investment in managing weed problems in the temperate pasture areas. One focus of that research has been on the development of improved management practices for the major annual grass weed vulpia. Recent surveys have found that weeds comprised up to 80% of pasture biomass in some temperate areas and that typical vulpia contents are between 30 and 40% of pasture biomass. Temperate pasture degradation is recognised as being a major contributor to the wider environmental problems of soil erosion, salinity and acidity. This evaluation related to a project (1996-2002) that focussed on the vulpia problem in the New South Wales temperate pasture areas. The benefits of that research were measured as the difference in the economic returns from the project (the with-research scenario) and those that would have resulted if the project had not been initiated (the without-research scenario). The results indicated high levels of economic benefits from the vulpia project. The annual net project benefit had a mean value of 196.9 million and a mean BCR of 22.2. These results demonstrate that research by NSW Agriculture into the improved management of vulpia has the potential to generate substantial long-term economic benefits. Other socio-economic aspects of the results showed that wool producers outside the New South Wales temperate areas lost economic surplus (from a mean -47.8 million) because they were unable to adopt the cost-reducing technology and faced a reduced wool price. All wool consumers gained from vulpia research because of expanded wool production and lower wool prices. Improved vulpia management is also considered to produce important environmental benefits by encouraging a greater use of deep-rooted perennial grasses and the beneficial effects of these on mitigating soil problems and reducing water table discharges.benefit cost analysis, research evaluation, annual grass weeds, vulpia, Research and Development/Tech Change/Emerging Technologies, Q160,
Generation of Large Number-Path Entanglement Using Linear Optics and Feed-Forward
We show how an idealised measurement procedure can condense photons from two
modes into one, and how, by feeding forward the results of the measurement, it
is possible to generate efficiently superpositions of components for which only
one mode is populated, commonly called ``N00N states''. For the basic
procedure, sources of number states leak onto a beam splitter, and the output
ports are monitored by photodetectors. We find that detecting a fixed fraction
of the input at one output port suffices to direct the remainder to the same
port with high probability, however large the initial state. When instead
photons are detected at both ports, Schr\"{o}dinger cat states are produced. We
describe a circuit for making the components of such a state orthogonal, and
another for subsequent conversion to a N00N state. Our approach scales
exponentially better than existing proposals. Important applications include
quantum imaging and metrology
Practical figures of merit and thresholds for entanglement distribution in quantum networks
Before global-scale quantum networks become operational, it is important to
consider how to evaluate their performance so that they can be built to achieve
the desired performance. We propose two practical figures of merit for the
performance of a quantum network: the average connection time and the average
largest entanglement cluster size. These quantities are based on the generation
of elementary links in a quantum network, which is a crucial initial
requirement that must be met before any long-range entanglement distribution
can be achieved and is inherently probabilistic with current implementations.
We obtain bounds on these figures of merit for a particular class of quantum
repeater protocols consisting of repeat-until-success elementary link
generation followed by joining measurements at intermediate nodes that extend
the entanglement range. Our results lead to requirements on quantum memory
coherence times, requirements on repeater chain lengths in order to surpass the
repeaterless rate limit, and requirements on other aspects of quantum network
implementations. These requirements are based solely on the inherently
probabilistic nature of elementary link generation in quantum networks, and
they apply to networks with arbitrary topology.Comment: 17 pages, 7 figures. v2: extensively revised and rewritten. Title and
abstract modified; added a section on overcoming the repeaterless rate limit;
modified statement of Theorem 1. v3: minor changes to match the published
versio
- …