What would a US policy of 'restraint' mean for the Warsaw NATO Summit?

This review discusses how a decision by the United States to pursue the policy recommended by Barry Posen in his book ‘Restraint’ would play out in the NATO alliance. The review does so by examining what ‘restraint’ would mean for how the alliance faces the problems of European divisions (including a potential Brexit and unravelling or fragmentation of the European Union), continued low levels of European defence spending, European perceptions of US indifference, high-handedness and isolationist attitudes in its presidential race, the spectre of Russian aggression and involvement in the Middle East, and ongoing debates about the alliance’s purpose in the face of challenges ranging from traditional military threats through to the refugee crisis in the Mediterranean

Solid-state ensemble of highly entangled photon sources at rubidium atomic transitions

Semiconductor InAs/GaAs quantum dots grown by the Stranski-Krastanov method are among the leading candidates for the deterministic generation of polarization entangled photon pairs. Despite remarkable progress in the last twenty years, many challenges still remain for this material, such as the extremely low yield (<1% quantum dots can emit entangled photons), the low degree of entanglement, and the large wavelength distribution. Here we show that, with an emerging family of GaAs/AlGaAs quantum dots grown by droplet etching and nanohole infilling, it is possible to obtain a large ensemble (close to 100%) of polarization-entangled photon emitters on a wafer without any post-growth tuning. Under pulsed resonant two-photon excitation, all measured quantum dots emit single pairs of entangled photons with ultra-high purity, high degree of entanglement (fidelity up to F=0.91, with a record high concurrence C=0.90), and ultra-narrow wavelength distribution at rubidium transitions. Therefore, a solid-state quantum repeater - among many other key enabling quantum photonic elements - can be practically implemented with this new material

ADM-Aeolus pre-launch activities and recent advances in spaceborne and airborne Wind Lidar Systems

The first space-borne wind lidar mission ADM-Aeolus from ESA is currently scheduled for launch by mid-2017. For the preparation of the Aeolus validation, an airborne field experiment was performed during 3 weeks in May 2015 with the DLR Falcon and the NASA DC-8 aircraft. For the first time 4 wind lidars were deployed during an airborne campaign including two coherent and two direct-detection wind lidars at a wavelength of 2μm and 355 nm. A total of 7 coordinated flights of the Falcon and DC-8 yielded an extensive dataset. Additionally, DLR’s airborne coherent Doppler Wind Lidar was recently deployed in 3 coordinated airborne campaigns aiming to investigate the life cycle of gravity waves from ground up to the mesosphere. The horizontal and vertical wind measurements of the lidar provide valuable data for characterizing tropospheric gravity waves and background wind conditions

Correlation between safety attitudes and early adoption of cognitive aids in the German culture sphere: a multicenter survey study

Background: Cognitive Aids (checklists) are a common tool to improve patient safety. But the factors for their successful implementation and continuous use are not yet fully understood. Recent publications suggest safety culture to play a key role in this context. However, the effects on the outcome of implementation measures remain unclear. Hospitals and clinics that are involved in cognitive aid development and research might have significantly different safety cultures than their counterparts, resulting in skewed assessments of proper implementation. Therefore, the objective of this study was to assess the correlation between cognitive aid implementation and safety attitudes of staff members in early adopting and later adopting clinics. Methods: An online survey of the Safety Attitudes Questionnaire (SAQ) was carried out in German anaesthesiology departments during the initial implementation of a new checklist for emergencies during anesthesia (“eGENA” app). Subsequently an analysis between subgroups (“eGENA” app usage and occupation), with Kruskal–Wallis- and Mann–Whitney-U-Tests was carried out for the general SAQ, as well as it six subscales. Results: Departments that introduced “eGENA” app (Median 3,74, IQR 0,90) reported a significantly higher median SAQ (U (NeGENA = 6, Nnon eGENA = 14) = 70,0, z = 2,31, p = 0,02, r = 0,516) than their counterparts (Median 2,82, IQR 0,77) with significant differences in the dimensions teamwork climate, work satisfaction, perception of management and working conditions. Conclusion: Early adopters of cognitive aids are likely to show a significantly higher perception of safety culture in the SAQ. Consequently, successful implementation steps from these settings might not be sufficient in different clinics. Therefore, further investigation of the effects of safety culture on cognitive aid implementation should be conducted

Wavelength-tunable entangled photons from silicon-integrated III–V quantum dots

Many of the quantum information applications rely on indistinguishable sources of polarization-entangled photons. Semiconductor quantum dots are among the leading candidates for a deterministic entangled photon source; however, due to their random growth nature, it is impossible to find different quantum dots emitting entangled photons with identical wavelengths. The wavelength tunability has therefore become a fundamental requirement for a number of envisioned applications, for example, nesting different dots via the entanglement swapping and interfacing dots with cavities/atoms. Here we report the generation of wavelength-tunable entangled photons from on-chip integrated InAs/GaAs quantum dots. With a novel anisotropic strain engineering technique based on PMN-PT/silicon micro-electromechanical system, we can recover the quantum dot electronic symmetry at different exciton emission wavelengths. Together with a footprint of several hundred microns, our device facilitates the scalable integration of indistinguishable entangled photon sources on-chip, and therefore removes a major stumbling block to the quantum-dot-based solid-state quantum information platforms

Landslides in mountainous regions of Northern Vietnam : causes, protection strategies and the assessment of economic losses

Landslides are a severe problem during the rainy season in many mountainous regions in Asia where forests have been cut so that mountain slopes are destabilized. In this study we analyze the extent and causes of landslides in a mountainous area in Northern Vietnam as viewed from the perspective of the concerned population. We also scrutinize the ideas of these people regarding suitable landslide protection measures and their willingness to contribute to the practical implementation of these measures. It shows that nearly all people living in this area feel highly concerned about the frequent landslide events and that they support the idea of government programs to mitigate the danger of future landslides. We measure the utility they expect from such a landslide protection program, i. e. the social value of such a program, in terms of their willingness to contribute personally to its implementation. Since budgets are tight in these rural areas where subsistence farming still prevails we also analyze the possibilities to measure these expected utility gains in terms of people's willingness to contribute working time instead of money to the proposed landslide protection program. The prospect of employing such an alternative means of contribution is, however, seen rather critical

Crystal Orientation Dependent Oxidation Modes at the Buried Graphene-Cu Interface.

We combine spatially resolved scanning photoelectron spectroscopy with confocal Raman and optical microscopy to reveal how the oxidation of the buried graphene-Cu interface relates to the Cu crystallographic orientation. We analyze over 100 different graphene covered Cu (high and low index) orientations exposed to air for 2 years. Four general oxidation modes are observed that can be mapped as regions onto the polar plot of Cu surface orientations. These modes are (1) complete, (2) irregular, (3) inhibited, and (4) enhanced wrinkle interface oxidation. We present a comprehensive characterization of these modes, consider the underlying mechanisms, compare air and water mediated oxidation, and discuss this in the context of the diverse prior literature in this area. This understanding incorporates effects from across the wide parameter space of 2D material interface engineering, relevant to key challenges in their emerging applications, ranging from scalable transfer to electronic contacts, encapsulation, and corrosion protection

Temperature-dependent coercive field measured by a quantum dot strain gauge

Coercive fields of piezoelectric materials can be strongly influenced by environmental temperature. We investigate this influence using a hetero-structure consisting of a single crystal piezoelectric film and a quantum dots containing membrane. Applying electric field leads to a physical deformation of the piezoelectric film, thereby inducing strain in the quantum dots and thus modifying their optical properties. The wavelength of the quantum dot emission shows butterfly-like loops, from which the coercive fields are directly derived. The results suggest that coercive fields at cryogenic temperatures are strongly increased, yielding values several tens of times larger than those at room temperature. We adapt a theoretical model to fit the measured data with very high agreement. Our work provides an efficient framework for predicting the properties of ferroelectric materials and advocate their practical applications, especially at low temperatures. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nano Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.nanolett.7b0413

Statistical limits for entanglement swapping with semiconductor entangled photon sources

Semiconductor quantum dots are promising building blocks for quantum communication applications. Al- though deterministic, efficient, and coherent emission of entangled photons has been realized, implementing a practical quantum repeater remains outstanding. Here we explore the statistical limits for entanglement swapping with sources of polarization-entangled photons from the commonly used biexciton-exciton cascade. We stress the necessity of tuning the exciton fine structure, and explain why the often observed time evolution of photonic entanglement in quantum dots is not applicable for large quantum networks. We identify the critical, statistically distributed device parameters for entanglement swapping based on two sources. A numerical model for benchmarking the consequences of device fabrication, dynamic tuning techniques, and statistical effects is developed, in order to bring the realization of semiconductor-based quantum networks one step closer to reality. ©2022 American Physical Societ