Optical diode based on the chirality of guided photons

Photons are nonchiral particles: their handedness can be both left and right. However, when light is transversely confined, it can locally exhibit a transverse spin whose orientation is fixed by the propagation direction of the photons. Confined photons thus have chiral character. Here, we employ this to demonstrate nonreciprocal transmission of light at the single-photon level through a silica nanofibre in two experimental schemes. We either use an ensemble of spin-polarised atoms that is weakly coupled to the nanofibre-guided mode or a single spin-polarised atom strongly coupled to the nanofibre via a whispering-gallery-mode resonator. We simultaneously achieve high optical isolation and high forward transmission. Both are controlled by the internal atomic state. The resulting optical diode is the first example of a new class of nonreciprocal nanophotonic devices which exploit the chirality of confined photons and which are, in principle, suitable for quantum information processing and future quantum optical networks

Large violation of Bell inequalities with low entanglement

In this paper we obtain violations of general bipartite Bell inequalities of order $\frac{\sqrt{n}}{\log n}$ with $n$ inputs, $n$ outputs and $n$-dimensional Hilbert spaces. Moreover, we construct explicitly, up to a random choice of signs, all the elements involved in such violations: the coefficients of the Bell inequalities, POVMs measurements and quantum states. Analyzing this construction we find that, even though entanglement is necessary to obtain violation of Bell inequalities, the Entropy of entanglement of the underlying state is essentially irrelevant in obtaining large violation. We also indicate why the maximally entangled state is a rather poor candidate in producing large violations with arbitrary coefficients. However, we also show that for Bell inequalities with positive coefficients (in particular, games) the maximally entangled state achieves the largest violation up to a logarithmic factor.Comment: Reference [16] added. Some typos correcte

Der Einfluss von reduzierter Bodenbearbeitung und Zwischenfrüchten auf die Unkrautsamenbank nach ökologischem Winterweizen- und Kartoffelbau

Conservation agriculture is one answer to counteract problems that are arising with climate change and soil degradation since the period of agricultural intensification. The main objectives of conservation agriculture are reduction of tillage intensity and a permanent soil cover by cash and cover crops. However, increased weed infestations are frequently reported in minimum tillage systems, particularly under organic management, resulting in increased weed seed banks. In two field experiments introduced in 2010 and 2011 and starting with two years grass-clover followed by winter wheat and potatoes, we evaluated the effect of chisel ploughing with mulch application to potatoes and different cover crops after winter wheat on the weed seed bank. Therefore, soil cores were taken before sowing wheat and after potato harvest and the viable weed seed bank from soil samples was assessed over a nine month period. Our results suggested a strong influence of weather conditions resulting in decreased and increased weed seed banks in the first and second experiments, respectively. Furthermore, winter wheat was confirmed as the main contributor of weed seeds to the seed bank resulting in dominances of winter annual weeds

Einflüsse von Minimalbodenbearbeitung und Transfermulch auf den Initialbefall und die Populationsentwicklung des Kartoffelkäfers (Leptinotarsa decemlineata)

The growing economic importance of potatoes in organic agriculture has led to the intensification of potato production and farm specialization. This has in turn increased the occurrence of the Colorado potato beetle, the most important potato insect pest worldwide. The effects of the application of green manure mulch to potatoes, which improves water and nutrient availability were investigated in a long-term field experiment, comparing two potato cultivation systems: conventional ploughing and hilling versus reduced tillage with dead mulch application. There were no differences in the initial degree of potato beetle infestation. However, a significant reduction in the number of potato beetle larvae and eggs was observed. The mechanism behind the effects should examined in future experiments

Connes' embedding problem and Tsirelson's problem

We show that Tsirelson's problem concerning the set of quantum correlations and Connes' embedding problem on finite approximations in von Neumann algebras (known to be equivalent to Kirchberg's QWEP conjecture) are essentially equivalent. Specifically, Tsirelson's problem asks whether the set of bipartite quantum correlations generated between tensor product separated systems is the same as the set of correlations between commuting C*-algebras. Connes' embedding problem asks whether any separable II$_1$ factor is a subfactor of the ultrapower of the hyperfinite II$_1$ factor. We show that an affirmative answer to Connes' question implies a positive answer to Tsirelson's. Conversely, a positve answer to a matrix valued version of Tsirelson's problem implies a positive one to Connes' problem

Global complexity: some remarks to the "Author meets critic session" at the DGS congress in 2004

Der Beitrag dokumentiert die Diskussion auf der "Author Meets Critic"-Veranstaltung zu John Urrys "Sociology Beyond Societies" auf dem 32. Kongress der Deutschen Gesellschaft für Soziologie (2004). Zunächst erläutert Urry den Grundgedanken seines Ansatzes, der auf eine Aufhebung der Trennung zwischen Naturwissenschaften und Gesellschaftswissenschaften hinausläuft. Unter dem Leitbild "Komplexität" wird die Analyse physischer und sozialer Welten integriert. Dabei werden auch Elemente von Hardt/Negris "Empire und Multitude"-Konzept aufgegriffen. Der Begriff der Globalen Komplexität steht auch im Mittelpunkt der Kommentare von Junge und Schwengel zu Urrys Buch. (ICE

Selective reductive amination of aldehydes from nitro compounds catalyzed by molybdenum sulfide clusters

Secondary amines are selectively obtained from low value starting materials using hydrogen and a non-noble metal-based catalyst. The reductive amination of aldehydes from nitroarenes or nitroalkanes is efficiently catalyzed by a well-defined diamino molybdenum sulfide cluster in a one-pot homogeneous reaction. The integrity of the molecular cluster catalyst is preserved along the process

Микропроцессорный блок управления полупроводниковым коммутатором для накачки CUBR-лазера

Разработка приборов, позволяющих проводить обработку материалов с помощью высококонцентрированных потоков энергии, является весьма актуальной задачей. Одним из классов таких приборов являются лазерные системы, которые могут применяться как в технике, так и в медицине. Разработка устройств, позволяющих формировать «силовой» пучок с заданной конфигурацией позволит значительно увеличить скорость обработки материалов и минимизировать побочные действия при использовании в медицинских целях. В работе представлено подобное устройство, позволяющее изменять распределение интенсивности по пучку с использованием активных оптических систем с усилителями яркости на парах металлов. В качестве усилителя яркости использовался CuBr-лазер с тиратронным источником питания с импульсным зарядом рабочей емкости. Мощность источника питания варьировалась от 900 до 1500 Вт. Проведены исследования зависимости контраста получаемых изображений и влияние параметров используемого дисплея