41 research outputs found
On structural physical approximations and entanglement breaking maps
No full textVery recently, a conjecture saying that the so-called structural physical approximations (SPAs) to optimal positive maps (optimal entanglement witnesses) give entanglement breaking (EB) maps (separable states) has been posed (Korbicz et al 2008 Phys. Rev. A 78 062105). The main purpose of this contribution is to explore this subject. First, we extend the set of entanglement witnesses supporting the conjecture. Then, we ask whether SPAs constructed from other than the depolarizing channel maps also lead to EB maps and show that in general this is not the case. On the other hand, we prove an interesting fact that for any positive map Lambda, there exists an EB channel Phi such that the SPA of Lambda constructed with the aid of Phi is again an EB channel. Finally, we ask similar questions in the case of continuous variable systems. We provide a simple way of constructing SPA and prove that in the case of the transposition map it gives the EB channel.
Energy management in smart grids - research potential of laboratory LINTE^2
No full textW związku z planowanym począwszy od 2016 r. wycofywaniem przestarzałych bloków w polskich elektrowniach, generacja mocy i energii elektrycznej w Polsce będzie maleć zmniejszając dostępne rezerwy. Jednym z kierunków mającym na celu poprawę bezpieczeństwa elektroenergetycznego kraju w takiej sytuacji może stać się między innymi rozwój technologii sieci elektroenergetycznych typu Smart Grid i efektywne zarządzanie energią elektryczną w takich sieciach. Wyzwania stojące przed polską elektroenergetyką w związku z wdrażaniem całkowicie nowych rozwiązań technicznych i organizacyjnych będą wymagały wsparcia ze strony uczelni i jednostek naukowych. Jednym z takich przedsięwzięć, ukierunkowanym na wsparcie rozwoju sieci Smart Grid, jest stworzenie na Wydziale Elektrotechniki i Automatyki Politechniki Gdańskiej ultranowoczesnego obiektu badawczego - Laboratorium Innowacyjnych Technologii Elektroenergetycznych i Integracji Odnawialnych Źródeł Energii LINTE^2.In 2016, a withdrawal of obsolete units from Polish power plants will be started. Consequently, power generation will decrease and available reserves will be reduced. Development of electricity networks called Smart Grid and effective management of electrical energy in such networks may be a way out to improve the country's power security in such a situation. The challenges facing the Polish power sector in implementing a completely new technical solutions will require support from universities and research units. One of these projects, aimed at supporting the development of Smart Grid is the creation of Laboratory LINTE^2 at the Department of Electrical and Control Engineering of Technical University of Gdansk
W-like bound entangled states and secure key distillation
No full textWe construct multipartite entangled states with underlying W-type structure satisfying positive partial transpose (PPT) condition under any partition. Then we show how to distill a N-partite secure key from the states using two different methods: direct application of local filtering and novel random key distillation scheme in which we adopt the idea from recent results on entanglement distillation. Open problems and possible implications are also discussed
All genuinely entangled stabilizer subspaces are multipartite fully nonlocal
No full textAbstract Understanding which entangled states give rise to Bell nonlocality and thus are resourceful in the device-independent framework is a long-standing unresolved problem. Here, we establish the equivalence between genuine entanglement and genuine nonlocality for a broad class of multipartite (pure and mixed) states originating from the stabilizer formalism. In fact, we prove that any (mixed) stabilizer state defined on a genuinely entangled subspace is multipartite fully nonlocal, meaning that it gives rise to correlations with no contribution from local hidden variable models of any type. Importantly, we also derive a lower bound on genuine nonlocality content of arbitrary multipartite states, opening the door to its experimental estimation
Concept of platform for sharing information about cyber-security incidents in the national power system
No full textArtykuł opisuje wybrane zagadnienia związane z cyberbezpieczeństwem w sektorze elektroenergetyki. Jednym z elementów zapewniania bezpieczeństwa sieci elektroenergetycznej jest efektywna wymiana informacji o incydentach bezpieczeństwa. W jej ramach wszystkie zaangażowane podmioty systemu elektroenergetycznego, tj.: elektrownie, operatorzy systemów przesyłowych, operatorzy systemów dystrybucyjnych, dostawcy rozwiązań bezpieczeństwa, organizacje standaryzujące, a także centra badawcze i środowiska akademickie, powinni móc dzielić się między sobą informacjami dotyczącymi incydentów bezpieczeństwa w systemie elektroenergetycznym. W referacie opisano ideę zastosowania do tego celu systemów wieloagentowych. Ponieważ sytuacja formalno-prawna podmiotów związanych z systemem elektroenergetycznym jest bardzo złożona, prowadzenie prac badawczo-rozwojowych w zakresie cyberbezpieczeństwa są znacznie ograniczone, a niekiedy niemożliwe. W referacie przedstawiono możliwości badawcze jakie w tym zakresie oferuje laboratorium LINTE^2.The article describes selected issues related to cybersecurity in the electric power sector. One of the aspects of providing power grid security is the effective exchange of information on security incidents. Under the framework, all the actors of the power system, ie .: power plants, transmission system operators, distribution system operators, suppliers of security solutions, standardization organizations, as well as research centers and academia, should be able to share information with each other on security incidents in the power system. The paper describes the idea of using multi-agent systems for this purpose. As the formal and legal circumstances of power system entities are very complex, possibilities of conducting research and development in the field of cybersecurity are significantly reduced, and sometimes impossible. The paper presents the research capabilities in this area, offered by the Laboratory LINTE^2
A note on the optimality of decomposable entanglement witnesses and completely entangled subspaces
No full textEntanglement and the three-dimensionality of the Bloch ball
No full textWe consider a very natural generalization of quantum theory by letting the dimension of the Bloch ball be not necessarily three. We analyze bipartite state spaces where each of the components has a d-dimensional Euclidean ball as state space. In addition to this we impose two very natural assumptions: the continuity and reversibility of dynamics, and the possibility of characterizing bipartite states by local measurements. We classify all these bipartite state spaces and prove that, except for the quantum two-qubit state space, none of them contains entangled states. Equivalently, in any of these non-quantum theories interacting dynamics is impossible. This result reveals that "existence of entanglement" is the requirement with minimal logical content which singles out quantum theory from our family of theories
Scalable Bell inequalities for graph states of arbitrary prime local dimension and self-testing
No full textConstructing genuinely entangled multipartite states with applications to local hidden variables and local hidden states models
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