Limitations of quantum computing with Gaussian cluster states

We discuss the potential and limitations of Gaussian cluster states for measurement-based quantum computing. Using a framework of Gaussian projected entangled pair states (GPEPS), we show that no matter what Gaussian local measurements are performed on systems distributed on a general graph, transport and processing of quantum information is not possible beyond a certain influence region, except for exponentially suppressed corrections. We also demonstrate that even under arbitrary non-Gaussian local measurements, slabs of Gaussian cluster states of a finite width cannot carry logical quantum information, even if sophisticated encodings of qubits in continuous-variable (CV) systems are allowed for. This is proven by suitably contracting tensor networks representing infinite-dimensional quantum systems. The result can be seen as sharpening the requirements for quantum error correction and fault tolerance for Gaussian cluster states, and points towards the necessity of non-Gaussian resource states for measurement-based quantum computing. The results can equally be viewed as referring to Gaussian quantum repeater networks.Comment: 13 pages, 7 figures, details of main argument extende

Percolation, renormalization, and quantum computing with non-deterministic gates

We apply a notion of static renormalization to the preparation of entangled states for quantum computing, exploiting ideas from percolation theory. Such a strategy yields a novel way to cope with the randomness of non-deterministic quantum gates. This is most relevant in the context of optical architectures, where probabilistic gates are common, and cold atoms in optical lattices, where hole defects occur. We demonstrate how to efficiently construct cluster states without the need for rerouting, thereby avoiding a massive amount of conditional dynamics; we furthermore show that except for a single layer of gates during the preparation, all subsequent operations can be shifted to the final adapted single qubit measurements. Remarkably, cluster state preparation is achieved using essentially the same scaling in resources as if deterministic gates were available.Comment: 5 pages, 4 figures, discussion of strategies to deal with further imperfections extended, references update

Canton Gymnastics Academy

Canton Gymnastics Academy (CGA) will offer many different programs for athletes looking to enter a cheerleading or gymnastics program. The focus will be on providing professional, knowledgeable advice and training to all athletes who enter the doors. As with any sport, CGA will ensure that athletes know correct techniques to execute skills they are learning. This will help ensure that they suffer less bodily injuries throughout their career and they\u27ll have less issues as adults. CGA will be registered as a Limited Liability Company (LLC) with the state of Michigan. Specifically, CGA will provide two program areas, each with different programs within. The first area will be cheerleading. In this program, Canton Gymnastics Academy will offer both recreational classes and a competitive team. Each of which will be explained later in this plan. The second area will be gymnastics; the main focus of the gym. This program will consist of recreational classes and a competitive team as well, however, due to the nature of the sport and the crowd it attracts, this program will be on a larger scale than the cheerleading program

How do you spell “freedom”? Narratives about the 25 April 1974 Revolution in the Brazilian press

This paper proposes a recomposition of the intrigue of journalistic narratives on the Revolution of April 25, 1974 in Portugal based on the coverage of two Brazilian newspapers: O Estado de S. Paulo and Jornal do Brasil. The journalistic narrative is understood as a time orderer in the contemporaneity, expressing a “generalized circulation of historical perception” (Nora, 1979, p. 180), mobilized by the emergence of a new phenomenon: the event. The unusual coup d’état in Portugal stirred the world’s political imagination, reviving confrontations between left and right. At that moment, in Brazil, the military dictatorship completed 10 years and the fourth president of the Armed Forces was beginning its mandate. Narratives are analyzed from different points of view: the organization of facts in time, the construction of characters, projections for the future, or the re-signification of the past

Directly estimating non-classicality

We establish a method of directly measuring and estimating non-classicality - operationally defined in terms of the distinguishability of a given state from one with a positive Wigner function. It allows to certify non-classicality, based on possibly much fewer measurement settings than necessary for obtaining complete tomographic knowledge, and is at the same time equipped with a full certificate. We find that even from measuring two conjugate variables alone, one may infer the non-classicality of quantum mechanical modes. This method also provides a practical tool to eventually certify such features in mechanical degrees of freedom in opto-mechanics. The proof of the result is based on Bochner's theorem characterizing classical and quantum characteristic functions and on semi-definite programming. In this joint theoretical-experimental work we present data from experimental optical Fock state preparation, demonstrating the functioning of the approach.Comment: 4+1 pages, 2 figures, minor change

Directed percolation effects emerging from superadditivity of quantum networks

Entanglement indcued non--additivity of classical communication capacity in networks consisting of quantum channels is considered. Communication lattices consisiting of butterfly-type entanglement breaking channels augmented, with some probability, by identity channels are analyzed. The capacity superadditivity in the network is manifested in directed correlated bond percolation which we consider in two flavours: simply directed and randomly oriented. The obtained percolation properties show that high capacity information transfer sets in much faster in the regime of superadditive communication capacity than otherwise possible. As a byproduct, this sheds light on a new type of entanglement based quantum capacity percolation phenomenon.Comment: 6 pages, 4 figure

Experimental implementation of the optimal linear-optical controlled phase gate

We report on the first experimental realization of optimal linear-optical controlled phase gates for arbitrary phases. The realized scheme is entirely flexible in that the phase shift can be tuned to any given value. All such controlled phase gates are optimal in the sense that they operate at the maximum possible success probabilities that are achievable within the framework of any postselected linear-optical implementation. The quantum gate is implemented using bulk optical elements and polarization encoding of qubit states. We have experimentally explored the remarkable observation that the optimum success probability is not monotone in the phase.Comment: 4 pages, 5 figures, 1 tabl

Interaction in cyberspace and cognitive training stimulate the areas of attention and memory in elderly people

A interação por meio do computador pode constituir uma alternativa para desenvolver a cognição em pessoas idosas. O objetivo do estudo foi avaliar as funções cognitivas das pessoas idosas que participaram de processos de interação em uma rede social na internet. A pesquisa é do tipo clínico randomizado, intervencionista e de caráter descritivo-analítico. A amostra do estudo foi composta por 41 mulheres idosas do Brasil. As idosas foram avaliadas neuropsicologicamente pré e pós intervenção. Para análise dos dados foi utilizado o teste Friedman. O nível de significância utilizado foi p _ 0,05. Os resultados indicaram uma melhora significativa nas funções cognitivas de atenção e memória nos grupos de intervenção e déficits cognitivos no grupo controle nas áreas de percepção, linguagem e praxias. Realizar treinamento cognitivo em redes sociais na internet pode melhorar algumas funções cognitivas de pessoas idosas, contribuindo para um envelhecimento ativo e com qualidade.The computer interaction may be an alternative to developing cognition in older people. The objective of the study was to evaluate the cognitive functions of elderly people who participated in interaction processes in a social network on the Internet. The research is a randomized, interventional and descriptive-analytical clinical type. The study sample consisted of 41 elderly women from Brazil. The elderly were assessed neuropsychologically before and after the intervention process. The Friedman test was used to analyze the data. The level of significance was p _ 0.05. The results indicated a significant improvement in the cognitive functions of attention and memory in intervention groups and cognitive deficits in the control group in the areas of perception, language and praxis. Cognitive training on social networks on the Internet can improve some cognitive functions of older people, contributing to active and quality ageinfo:eu-repo/semantics/publishedVersio