7,247 research outputs found

    Extra Shared Entanglement Reduces Memory Demand in Quantum Convolutional Coding

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    We show how extra entanglement shared between sender and receiver reduces the memory requirements for a general entanglement-assisted quantum convolutional code. We construct quantum convolutional codes with good error-correcting properties by exploiting the error-correcting properties of an arbitrary basic set of Pauli generators. The main benefit of this particular construction is that there is no need to increase the frame size of the code when extra shared entanglement is available. Then there is no need to increase the memory requirements or circuit complexity of the code because the frame size of the code is directly related to these two code properties. Another benefit, similar to results of previous work in entanglement-assisted convolutional coding, is that we can import an arbitrary classical quaternary code for use as an entanglement-assisted quantum convolutional code. The rate and error-correcting properties of the imported classical code translate to the quantum code. We provide an example that illustrates how to import a classical quaternary code for use as an entanglement-assisted quantum convolutional code. We finally show how to "piggyback" classical information to make use of the extra shared entanglement in the code.Comment: 7 pages, 1 figure, accepted for publication in Physical Review

    Study of EVA operations associated with satellite services

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    Extravehicular mobility unit (EMU) factors associated with satellite servicing activities are identified and the EMU improvements necessary to enhance satellite servicing operations are outlined. Areas of EMU capabilities, equipment and structural interfaces, time lines, EMU modifications for satellite servicing, environmental hazards, and crew training are vital to manned Eva/satellite services and as such are detailed. Evaluation of EMU capabilities indicates that the EMU can be used in performing near term, basic satellite servicing tasks; however, satellite servicing is greatly enhanced by incorporating key modifications into the EMU. The servicing missions involved in contamination sensitive payload repair are illustrated. EVA procedures and equipment can be standardized, reducing both crew training time and in orbit operations time. By standardizing and coordinating procedures, mission cumulative time lines fall well within the EMU capability

    Diplomatic asylum and extraterritorial non-refoulement: the foundational contribution of the Latin American region to extraterritorial human rights obligations

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    Diplomatic asylum—a state offering refuge in its diplomatic premises in a foreign state to an individual requiring protection from that foreign state, as happened with Julian Assange in the Ecuadorean Embassy in London—is a practice long associated with Latin American States. Although not usually thought of in this way, it can and should be viewed as an invocation of the notion that states should protect human rights extraterritorially. The nature and extent of extraterritorial human rights obligations is subject to considerable disagreement and dispute on the part of states, including, notably, in Europe. At the same time, it is often the European region that is commonly understood to have led developments in the international jurisprudence on extraterritoriality, via the case law under the European Convention on Human Rights mostly from the 1990s onwards. The present chapter challenges this narrative. Itsuggests that it is the Latin American region, through its much earlier normative commitment to diplomatic asylum, that can be regarded as having made the foundational international normative contribution to the concept of extraterritorial human rights obligations. Thisset a precedent that would only be recognized much later in international human rights law, including European human rights law

    Positronium collisions with rare-gas atoms

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    We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method [I. I. Fabrikant and G. F. Gribakin, Phys. Rev. A 90, 052717 (2014)] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr, and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (breakup). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.Comment: 7 pages, 7 figures, submitted to J. Phys.

    International recognition and human rights treaties

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    The chapter argues that international human rights treaties contain obligations with implications for the practice of recognition/non-recognition by states of other states and governments. It begins by explaining how international human rights treaty obligations relate to extraterritorial situations and how this might apply to the practice of recognition/non-recognition. It then explains how recognition/non-recognition practice is understood in international law. Following this, the chapter addresses what human rights treaty standards would require of recognition/non-recognition. Finally, consideration is given to the potential divergence in the human rights obligations of the recognizing/non-recognizing state, and the obligations of the object of that recognition/non-recognition

    Compliance with human rights norms extraterritorially: 'human rights imperialism'?

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