Quantum repeaters with individual rare-earth ions at telecommunication wavelengths

We present a quantum repeater scheme that is based on individual erbium and europium ions. Erbium ions are attractive because they emit photons at telecommunication wavelength, while europium ions offer exceptional spin coherence for long-term storage. Entanglement between distant erbium ions is created by photon detection. The photon emission rate of each erbium ion is enhanced by a microcavity with high Purcell factor, as has recently been demonstrated. Entanglement is then transferred to nearby europium ions for storage. Gate operations between nearby ions are performed using dynamically controlled electric-dipole coupling. These gate operations allow entanglement swapping to be employed in order to extend the distance over which entanglement is distributed. The deterministic character of the gate operations allows improved entanglement distribution rates in comparison to atomic ensemble-based protocols. We also propose an approach that utilizes multiplexing in order to enhance the entanglement distribution rate.Comment: 13 pages, 4 figure

Anthromes dispaying evidence of weekly cycles in active fire data cover 70% of the global land surface

Across the globe, human activities have been gaining importance relatively to climate and ecology as the main controls on fire regimes and consequently human activity became an important driver of the frequency, extent and intensity of vegetation burning worldwide. Our objective in the present study is to look for weekly cycles in vegetation fire activity at global scale as evidence of human agency, relying on the original MODIS active fire detections at 1 km spatial resolution (MCD14ML) and using novel statistical methodologies to detect significant periodicities in time series data. We tested the hypotheses that global fire activity displays weekly cycles and that the weekday with the fewest fires is Sunday. We also assessed the effect of land use and land cover on weekly fire cycle significance by testing those hypotheses separately for the Villages, Settlements, Croplands, Rangelands, Seminatural, and Wildlands anthromes. Based on a preliminary data analysis of the daily global active fire counts periodogram, we developed an harmonic regression model for the mean function of daily fire activity and assumed a linear model for the de-seasonalized time series. For inference purposes, we used a Bayesian methodology and constructed a simultaneous 95% credible band for the mean function. The hypothesis of a Sunday weekly minimum was directly investigated by computing the probabilities that the mean functions of every weekday (Monday to Saturday) are inside the credible band corresponding to mean Sunday fire activity. Since these probabilities are small, there is statistical evidence of significantly fewer fires on Sunday than on the other days of the week. Cropland, rangeland, and seminatural anthromes, which cover 70% of the global land area and account for 94% of the active fires analysed, display weekly cycles in fire activity. Due to lower land management intensity and less strict control over fire size and duration, weekly cycles in Rangelands and Seminatural anthromes, which jointly account for 53.46% of all fires, although statistically significant are weaker than those detected in Croplandsinfo:eu-repo/semantics/publishedVersio

Transition from Persistent to Anti-Persistent Correlations in Postural Sway Indicates Velocity-Based Control

The displacement of the center-of-pressure (COP) during quiet stance has often been accounted for by the control of COP position dynamics. In this paper, we discuss the conclusions drawn from previous analyses of COP dynamics using fractal-related methods. On the basis of some methodological clarification and the analysis of experimental data using stabilogram diffusion analysis, detrended fluctuation analysis, and an improved version of spectral analysis, we show that COP velocity is typically bounded between upper and lower limits. We argue that the hypothesis of an intermittent velocity-based control of posture is more relevant than position-based control. A simple model for COP velocity dynamics, based on a bounded correlated random walk, reproduces the main statistical signatures evidenced in the experimental series. The implications of these results are discussed

Mitigating risk of exceeding environmental limits requires ambitious food system interventions

Transforming the global food system is necessary to avoid exceeding planetary boundaries. A robust evidence base is crucial to assess the scale and combination of interventions required for a sustainable transformation. We developed a risk assessment framework, underpinned by a meta-regression of 60 global food system modeling studies, to quantify the potential of individual and combined interventions to mitigate the risk of exceeding the boundaries for land-system change, freshwater use, climate change, and biogeochemical flows by 2050. Limiting the risk of exceedance across four key planetary boundaries requires a high but plausible level of ambition in all demand-side (diet, population, waste) and most supply-side interventions. Attaining the required level of ambition for all interventions relies on embracing synergistic actions across the food system

Facebook’s ad hoc groups: a potential source of communicative power of networked citizens

Ad hoc groups (sporadically formed on social network sites for achieving particular common objectives) have been seen as a public space for citizen participation and debate. This study focuses on Facebook’s ad hoc groups in Finland. The aim is to detect the potential of these groups to enhance networked citizens’ communicative power for raising societally important issues to public agenda and initiate changes in society. We suggest a categorization of the groups according to their missions, and present their members’ specific motivations and objectives through an online survey. Despite the general entertainment-orientation and self-referential nature of social media, the results show that ambitions and objectives of ad hoc groups differ notably according to their main mission. Especially clear difference is found between discussion groups and those pursuing societal influence. In addition, media analysis is used to discover how much and for what reasons news media have used the specific groups as news sources. Although not strategically seeking media visibility, the societal influence groups gained larger news coverage, related to their thought-provoking topics, connections to current conditions, group membership size and potential to deal with issues of common concern

Combining biophysical modeling and Polanyian theory pleads for a re-embedding of the agricultural system in 2050 in Austria

International audienceLand use faces a double challenge: to provide biomass to a growing population while contributing to climate -change mitigation. We here scrutinize this challenge by exploring the domestic option space for meeting the food demand of Austria in 2050 under the condition of no deforestation. To that end, we bring together a quantitative assessment based on biogeochemical models with a socio-political analysis based on the conceptual framework of (dis-) embeddedness derived from Polanyian thinking. We consider viable options by modifying four levers: (i) human diet and food waste; (ii) trade patterns; (iii) agricultural practices; (iv) technical climate change mitigation. Past and present policies in Austria have fostered an agricultural system rich in animal products, land-use specialization and the integration of biomass products within international markets, ulti-mately resulting in a loss of embeddedness in the sense of Polanyi. The biophysical analysis, however, highlights that a shift towards diets with less animal products would allow increasing self-sufficiency or a generalization of organic farming while turning the agricultural and forestry sector into a net GHG sink. Following a Polanyian perspective, we show that feasible scenarios require different types of re-embedding of the agricultural system: ecological, spatial and social, implying that land products should rather be common goods than mere commodities