On the optimality of individual entangling-probe attacks against BB84 quantum key distribution

It is shown that an existing method to study ideal individual attacks on the BB84 QKD protocol using error discard can be adapted to reconciliation with error correction, and that an optimal attack can be explicitly found. Moreover, this attack fills Luetkenhaus bound, independently of whether error positions are leaked to Eve, proving that it is tight. In addition, we clarify why the existence of such optimal attacks is not in contradiction with the established ``old-style'' theory of BB84 individual attacks, as incorrectly suggested recently in a news feature.Comment: 12 pages, 3 figure

Quantitative determination of plant opal content in soils, using a combined method of heavy liquid separation and alkali dissolution

The aim of this study was to improve the quantitative determination of the plant opal content (i.e. phytoliths) in soils.The proposed method is based on: (i) the separation of plant opal from the silt and sand fractions of the soil, using heavy liquid flotation (aqueous solution of ZnBr2, density = 1.92 g cm−3); (ii) the subsequent determination of alkali-soluble silicon by atomic absorption spectrometry. Extraction and analytical procedures were tested on a broad sample of temperate and tropical soils with very different phytolith contents.Our investigations lead to the following conclusions: (i) a selective dissolution of opal in alkaline solutions (e.g. hot 0.5 m NaOH as proposed by Jones, 1969) is inaccurate so that a sink-float method must be used before any dissolution procedure; (ii) to dissolve opal completely, a 0.5 M NaOH dissolution treatment at 150°C can be easily and successfully carried out in steel PTFE-lined pressure vessels; (iii) the reproducibility of the determination is satisfactory for a step-by-step procedure (mean coefficient of variation = 13.4%).The comparison of this new method of quantitative assessment of soil opal with two other methods (gravimetric and phytolith-counting methods), shows very highly significant correlations (P<0.001). Therefore, this procedure is a useful tool in studies connected with pedological and environmental history.SCOPUS: ar.jFLWNAinfo:eu-repo/semantics/publishe