A Fair Sampling Test for Ekert Protocol

We propose a local scheme to enhance the security of quantum key distribution in Ekert protocol (E91). Our proposal is a fair sampling test meant to detect an eavesdropping attempt that would use a biased sample to mimic an apparent violation of Bell inequalities. The test is local and non disruptive: it can be unilaterally performed at any time by either Alice or Bob during the production of the key, and together with the Bell inequality test.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett

The Electrical Conductivity of Magnetite

The electrical conductivity of magnetite was measured in the temperature range including the transformation temperature. Measurements of single crystals showed a marked jump of conductivity at that temperature. The variation of conductivity with applied magnetic field is also measured and the amount of it was not so large as expected by the theory which assumes the transformation to be that of spontaneous magnetization. Previous theories are criticized on the basis of the experimental results obtained

On the Properties of Chromium Sulphides and Iron Sulphides. II

The experimental data on the electrical and magnetic properties of chromium sulphides and iron sulphides are discussed on the basis of itinerant electron model of semiconductors. As for the electronic structures of the said substances it is concluded that there is a conduction band which overlaps the electronic, energy bands responsible for the occurrence of ferromagnetism