Can observed randomness be certified to be fully intrinsic?

Randomness comes in two qualitatively different forms. Apparent randomness can result both from ignorance or lack of control of degrees of freedom in the system. In contrast, intrinsic randomness should not be ascribable to any such cause. While classical systems only possess the first kind of randomness, quantum systems are believed to exhibit some intrinsic randomness. In general, any observed random process includes both forms of randomness. In this work, we provide quantum processes in which all the observed randomness is fully intrinsic. These results are derived under minimal assumptions: the validity of the no-signalling principle and an arbitrary (but not absolute) lack of freedom of choice. The observed randomness tends to a perfect random bit when increasing the number of parties, thus defining an explicit process attaining full randomness amplification.Comment: 4 pages + appendice

Certifying the Absence of Apparent Randomness under Minimal Assumptions

Contrary to classical physics, the predictions of quantum theory for measurement outcomes are of a probabilistic nature. Questions about the completeness of such predictions lie at the core of quantum physics and can be traced back to the foundations of the field. Recently, the completeness of quantum probabilistic predictions could be established based on the assumption of freedom of choice. Here we ask when can events be established to be as unpredictable as we observe them to be relying only on minimal assumptions, ie. distrusting even the free choice assumption but assuming the existence of an arbitrarily weak (but non-zero) source of randomness. We answer the latter by identifying a sufficient condition weaker than the monogamy of correlations which allow us to provide a family of finite scenarios based on GHZ paradoxes where quantum probabilistic predictions are as accurate as they can possibly be. Our results can be used for a protocol of full randomness amplification, without the need of privacy amplification, in which the final bit approaches a perfect random bit exponentially fast on the number of parties

Groundwater influence on soil moisture memory and land–atmosphere fluxes in the Iberian Peninsula

Groundwater plays an important role in the terrestrial water cycle, interacting with the land surface via vertical fluxes through the water table and distributing water resources spatially via gravity-driven lateral transport. It is therefore essential to have a correct representation of groundwater processes in land surface models, as land–atmosphere coupling is a key factor in climate research. Here we use the LEAFHYDRO land surface and groundwater model to study the groundwater influence on soil moisture distribution and memory, and evapotranspiration (ET) fluxes in the Iberian Peninsula over a 10-year period. We validate our results with time series of observed water table depth from 623 stations covering different regions of the Iberian Peninsula, showing that the model produces a realistic water table, shallower in valleys and deeper under hilltops. We find patterns of shallow water table and strong groundwater–land surface coupling over extended interior semi-arid regions and river valleys. We show a strong seasonal and interannual persistence of the water table, which induces bimodal memory in the soil moisture fields; soil moisture “remembers” past wet conditions, buffering drought effects, and also past dry conditions, causing a delay in drought recovery. The effects on land–atmosphere fluxes are found to be significant: on average over the region, ET is 17.4 % higher when compared with a baseline simulation with LEAFHYDRO's groundwater scheme deactivated. The maximum ET increase occurs in summer (34.9 %; 0.54 mm d−1). The ET enhancement is larger over the drier southern basins, where ET is water limited (e.g. the Guadalquivir basin and the Mediterranean Segura basin), than in the northern Miño/Minho basin, where ET is more energy limited than water limited. In terms of river flow, we show how dry season baseflow is sustained by groundwater originating from accumulated recharge during the wet season, improving significantly on a free-drain approach, where baseflow comes from water draining through the top soil, resulting in rivers drying out in summer. Convective precipitation enhancement through local moisture recycling over the semi-arid interior regions and summer cooling are potential implications of these groundwater effects on climate over the Iberian Peninsula. Fully coupled land surface and climate model simulations are needed to elucidate this question.This research has been supported by the Spanish Department of Education and Science and by the European Commission (grant no. 603608: eartH2Observe). This study has also received funding from the UK National Environment Research Council (NERC), under the Hydro-JULES programme (grant no. NE/S017380/1)S

Transnational Firms and Cooperation Patterns in the Mediterranean: two Catalan-Aragonese Firms in the Fifteenth Century

This paper presents a methodological approach to the study of the increasingly efficient commercial and banking firms in late medieval Europe, based on the structural analysis of two major Mediterranean firms that operated from Zaragoza and Barcelona in the first half of the fifteenth century. The analysis of the cooperative mechanisms deployed by the socio-economic elite of the Crown of Aragon is brought to the foreground with special emphasis on human capital strategies, such as those reflected in the recruitment of commercial agents. We discuss a number of examples drawn from notarial records, account books and commercial correspondence in order to bring to light not only commercial relationships but also kinship and friendship ties

Randomness in post-selected events

Bell inequality violations can be used to certify private randomness for use in cryptographic applications. In photonic Bell experiments, a large amount of the data that is generated comes from no-detection events and presumably contains little randomness. This raises the question as to whether randomness can be extracted only from the smaller post-selected subset corresponding to proper detection events, instead of from the entire set of data. This could in principle be feasible without opening an analogue of the detection loophole as long as the min-entropy of the post-selected data is evaluated by taking all the information into account, including no-detection events. The possibility of extracting randomness from a short string has a practical advantage, because it reduces the computational time of the extraction. Here, we investigate the above idea in a simple scenario, where the devices and the adversary behave according to i.i.d. strategies. We show that indeed almost all the randomness is present in the pair of outcomes for which at least one detection happened. We further show that in some cases applying a pre-processing on the data can capture features that an analysis based on global frequencies only misses, thus resulting in the certification of more randomness. We then briefly consider non-i.i.d strategies and provide an explicit example of such a strategy that is more powerful than any i.i.d. one even in the asymptotic limit of infinitely many measurement rounds, something that was not reported before in the context of Bell inequalities.Comment: similar to published version, new section (III) on photonic experiment

De Martín I a Fernando I: Itinerario de un compromiso (1410-1412)

La muerte de Martín el Humano en mayo de 1410 significó el agravamiento de la crisis dinástica que padecía la Corona de Aragón desde que prácticamente un año antes, el 25 de julio de 1409, hubiese fallecido su hijo, Martín el Joven, dejando el trono sin heredero. Se iniciaba de este modo un turbulento interregno, de más de dos años de duración, que podemos dividir en tres grandes etapas. La primera de ellas incluye los meses transcurridos entre la muerte de Martín I, el 31 de mayo de 1410, y el asesinato del arzobispo de Za ragoza, el 1 de junio de 1411; la segunda etapa transcurre entre la convocatoria del Parlamento aragonés en Alcañiz y el traslado del catalán a Tortosa, entre los meses de julio y septiembre de 1411, y la aprobación de la Concordia de Alcañiz, el 15 de febrero de 1412; y la tercera abarca el desarrollo de la reunión de Caspe, desde su inicio, el día 29 de marzo, hasta la proclamación de Fernando I como rey, el 28 de junio de 1412

Hacer fortuna en la expansión mercantil bajomedieval. Tres grandes empresas de negocios zaragozanas a comienzos del siglo XV

Este trabajo presenta los resultados de mi tesis doctoral, queexplora los objetivos y estrategias de las tres mayores empresas mercantiles de Zaragoza entre 1380 y 1430. La investigación se ha basado un estudio de casos a partir de fuentes notariales para ofrecer una visión comparativa de los agentes sociales de la expansión comercial del reino de Aragón al final de la Edad Media. Este estudio profundiza en la abundante historiografía existente sobre mercados, economía institucional y elites urbanas, buscando contribuir a los debates actuales sobre formación del Estado moderno y desarrollo económico de la Europa premoderna