Man and the atom

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Quantum Logical Gates with Linear Quadripartite Cluster States of Continuous Variables

The concrete schemes to realize three types of basic quantum logical gates using linear quadripartite cluster states of optical continuous variables are proposed. The influences of noises and finite squeezing on the computation precision are analyzed in terms of the fidelity of propagated quantum information through the continuous variable cluster states. The proposed schemes provide direct references for the design of experimental systems of one-way quantum computer based on the cluster entanglement of amplitude and phase quadratures of light.Comment: accepted for publication by PR

Reflexiones de un físico

'Este es un humilde intento de un octogenario de pagar tributo al genio del siempre joven Bertrand Russell. Su nombre me fue conocido desde que llegué a Göttingen en 1903, como estudiante de matemáticas y física.' Tomado del libro "Homenaje a Bertrand RusseIl", recopilado por Ralph Schoenman

Energetic Polymers: A Chance for Lightweight Reactive Structure Materials?

Today's ammunition still consists of about 70 wt% structure-providing materials such as metals providing no energetic contribution. Therefore, reactive structure materials (RSMs) offer tremendous room for improvement. While current research focuses on rather heavy, metal-based materials (e. g., alloys, thermites), energetic polymers appear as an under-recognized opportunity for very lightweight RSMs. Unfortunately, suitable polymers are unavailable as energetic polymer research has almost exclusively focused on elastic binders with the least possible glass transition temperature. An application as RSM, however, requires rigid polymers with a glass transition above operational temperatures. Accordingly, monomers with fundamentally different structures are required. The first step in this particular direction is 3-(2,4,6-trinitrophenoxy)oxetane (TNPO). Herein, we report the synthesis of its homopolymer and investigate its polymerization behavior by copolymerization with prior art energetic oxetanes. All polymers were intensively studied by vibrational and multinuclear (H-1, C-13, N-14) NMR spectroscopy, elemental analysis, gel permeation chromatography, and differential scanning calorimetry (DSC). Hereby, DSC revealed the high effect of the TNPO repeating unit on the glass transition temperature. The performance of all polymers was calculated using the EXPLO5 code to evaluate the potential performance range of polymeric RSMs. Further, their shock and friction sensitivity was determined by BAM standard procedures

Improved Preparation of 3-Oximinooxetane - An Important Precursor to Energetic Oxetanes

Oximes represent an extremely versatile building block in energetic materials chemistry. While oxidation with peroxy acids affords the corresponding mononitro compounds, tandem oxidation-nitration reactions such as the Scholl reaction lead to geminal dinitro compounds. Furthermore, the corresponding amines can be obtained by reduction of the oxime group. Accordingly, 3-oximinooxetane represents a suitable precursor for 3-nitro- and 3,3-dinitrooxetane as well as 3-aminooxetane. 3-Oximinooxetane, which is poorly described in the literature, has now been extensively characterized by vibrational-, mass- and NMR spectroscopy, as well as elemental and thermal analysis. In addition, its synthesis has been significantly improved compared to literature. The molecular structure was elucidated by single-crystal X-ray diffraction. Since 3-oximinooxetane is energetic by itself, its performance was calculated using the EXPLO5 V6.04 thermochemical code, and its sensitivity towards external stimuli such as impact, friction, and electrostatic discharge was determined by BAM standard procedures

Oxetane Monomers Based On the Powerful Explosive LLM-116: Improved Performance, Insensitivity, and Thermostability

3-Bromomethyl-3-hydroxymethyloxetane represents an inexpensive and versatile precursor for the synthesis of 3,3-disubstituted oxetane derivatives. In the present work, its synthesis was improved and energetic oxetanes based on the explosive LLM-116 (4-amino-3,5-dinitro-1H-pyrazole) prepared. Reaching detonation velocities and pressures of up to 7335 ms(-1) and 20.9 GPa in combination with a high thermostability and insensitivity, these surpass the prior art by far. Next to a symmetric LLM-116 derivative, three asymmetric compounds were prepared using azido-, nitrato- and tetrazolyl-moieties. All compounds were intensively characterized by vibrational-, mass- and multinuclear (H-1, C-13, N-14) NMR spectroscopy, differential scanning calorimetry and elemental analysis. The molecular structures were elucidated by single crystal X-ray diffraction. Hirshfeld analysis allowed to estimate their sensitivity next to a practical evaluation using BAM standard procedures. Their performance was calculated using the EXPLO5 V6.04 code and a small-scale shock reactivity test and initiation test demonstrated their insensitivity and performance

Relativistic Attosecond Electron Bunches from Laser-Illuminated Droplets

The generation of relativistic attosecond electron bunches is observed in three-dimensional, relativistic particle-in-cell simulations of the interaction of intense laser light with droplets. The electron bunches are emitted under certain angles which depend on the ratios of droplet radius to wavelength and plasma frequency to laser frequency. The mechanism behind the multi-MeV attosecond electron bunch generation is investigated using Mie theory. It is shown that the angular distribution and the high electron energies are due to a parameter-sensitive, time-dependent local field enhancement at the droplet surface.Comment: 4 pages, 5 figures, REVTeX-styl

3-(Nitromethylene)oxetane: a very versatile and promising building block for energetic oxetane based monomers

In the field of energetic materials, older developments (e.g., RDX, ONC, CL20) are increasingly replaced by more environmentally benign, less expensive and likewise or more powerful compounds. This is mainly achieved through nitrogen-rich motifs like tetrazoles. However, such materials are mostly used as formulations containing polymeric energetic binders. Unfortunately, prior art binders show very poor performances and therefore reduce the overall performance. To address this problem, new monomers with enhanced performance are a prerequisite. Since the majority of energetic binders is oxetane-based, we chose 3-(nitromethylene)oxetane as a promising building block. It exhibits an explosophoric group, has recently become commercially available and provides suitable monomers by elegant and cost-efficient one-pot syntheses via conjugate addition. Herein, we report derivatives based on 1H-tetrazole, 1H-tetrazole-5-amine and the rather exotic but extremely powerful primary explosives 5-azido-1H-tetrazole (5AzT) and 5-nitro-2H-tetrazole (5NT). The sensitivities toward external stimuli like impact, friction, and electrostatic discharge were assessed by BAM standard procedures. As all molecular structures were elucidated by X-ray diffraction, Hirshfeld analysis was applied to explain the surprisingly low sensitivities found for the 5AzT- and 5NT-derivatives. Further, the compounds were studied by vibrational- and multinuclear NMR spectroscopy (H-1, C-13, N-14), differential scanning calorimetry, and elemental analysis. Their performance was calculated using the EXPLO5 V6.04 thermochemical code. Based on obtained values, the 5AzT- and 5NT-derivatives outperform prior art energetic oxetanes and TNT. Therefore, their performance was additionally demonstrated and evaluated by a small-scale shock reactivity test (SSRT)

J.S. Bell's Concept of Local Causality

John Stewart Bell's famous 1964 theorem is widely regarded as one of the most important developments in the foundations of physics. It has even been described as "the most profound discovery of science." Yet even as we approach the 50th anniversary of Bell's discovery, its meaning and implications remain controversial. Many textbooks and commentators report that Bell's theorem refutes the possibility (suggested especially by Einstein, Podolsky, and Rosen in 1935) of supplementing ordinary quantum theory with additional ("hidden") variables that might restore determinism and/or some notion of an observer-independent reality. On this view, Bell's theorem supports the orthodox Copenhagen interpretation. Bell's own view of his theorem, however, was quite different. He instead took the theorem as establishing an "essential conflict" between the now well-tested empirical predictions of quantum theory and relativistic \emph{local causality}. The goal of the present paper is, in general, to make Bell's own views more widely known and, in particular, to explain in detail Bell's little-known mathematical formulation of the concept of relativistic local causality on which his theorem rests. We thus collect and organize many of Bell's crucial statements on these topics, which are scattered throughout his writings, into a self-contained, pedagogical discussion including elaborations of the concepts "beable", "completeness", and "causality" which figure in the formulation. We also show how local causality (as formulated by Bell) can be used to derive an empirically testable Bell-type inequality, and how it can be used to recapitulate the EPR argument.Comment: 19 pages, 4 figure