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Resumen Describimos y analizamos los detalles de la primera visita del físico vienés Erwin Schrödinger a España, en verano de 1934. El motivo del viaje fue la invitación de la Universidad Internacional de Santander, cita a la que acudió después de intervenir en el XIV Congreso de la Asociación Española para el Progreso de las Ciencias que se celebró ese mismo verano en Santiago de Compostela. Discutiremos el impacto de esta visita en los primeros desarrollos de la mecánica cuántica en España y veremos el papel que tuvieron en este episodio personajes como Xavier Zubiri o Blas Cabrera. También pondremos esta visita en el contexto de la evolución personal y académica de Schrödinger, especialmente en lo que se refiere al contenido de sus intervenciones. Veremos que lo que presentó en Santiago y Santander debe considerarse un anticipo de su crítica a la interpretación ortodoxa de la nueva mecánica de los cuantos. Dejamos para una segunda entrega el viaje que realizó en la primavera de 1935, menos de un año después, esta vez junto a su esposa Annie, y en la que pronunció diversas conferencias y cursos sobre mecánica ondulatoria en Madrid. Abstract We describe and analyze the details of the first visit of the Viennese physicist Erwin Schrödinger to Spain, in the summer of 1934. The reason for the trip was the invitation he received from the International University of Santander, a meeting he attended after participating in the XIV Conference of the Spanish Association for the Advancement of Science that took place that same summer in Santiago de Compostela. We will discuss the impact of this visit on the first developments of quantum mechanics in Spain and see the role that personalities such as Xavier Zubiri or Blas Cabrera played in this episode. We will also put this visit in the context of Schrödinger’s personal and academic life, especially as regards the content of his talks. We will see that what he presented in Santiago and Santander should be considered as an advance of his criticism of the orthodox interpretation of quantum mechanics. We leave for a second installment the trip he made in the spring of 1935, less than a year later, this time with his wife Annie, and in which he delivered various conferences and courses on wave mechanics in Madrid. Palabras claves: Física, Mecánica cuántica, España, siglo XX. Key words: Physics, Quantum mechanics, Spain, XXth century.

For a system of N spins 1/2 there are quantum states that can encode a direction in an intrinsic way. Information on this direction can later be decoded by means of a quantum measurement. We present here the optimal encoding and decoding procedure using the fidelity as a figure of merit. We compute the maximal fidelity and prove that it is directly related to the largest zeroes of the Legendre and Jacobi polynomials. We show that this maximal fidelity approaches unity quadratically in 1/N. We also discuss this result in terms of the dimension of the encoding Hilbert space., Comment: 14 pages

Quantum states can be used to encode the information contained in a direction, i.e., in a unit vector. We present the best encoding procedure when the quantum state is made up of $N$ spins (qubits). We find that the quality of this optimal procedure, which we quantify in terms of the fidelity, depends solely on the dimension of the encoding space. We also investigate the use of spatial rotations on a quantum state, which provide a natural and less demanding encoding. In this case we prove that the fidelity is directly related to the largest zeros of the Legendre and Jacobi polynomials. We also discuss our results in terms of the information gain., 4 pages, RevTex, final version to appear in Phys.Rev.Lett

A través de la figura d'Albert Einstein, aquest escrit vol fer arribar la física als docents i també als infants, tot situant el personatge en el seu context. S'incideix, doncs, en el tema per dues bandes: una, la que integra la ciència en la cultura i, l'altra, la que facilita la familiarització amb una sèrie de conceptes

Després de repassar breument la història de la construcció, al segle XVIII, del castell de Sant Ferran de Figueres –una de les principals fortaleses baluardades d’Europa–, i d’analitzar les causes de la Guerra Gran (1793-1795) entre la monarquia espanyola i la República Francesa, es presenten els principals esdeveniments que portaren a la “inexplicable” rendició del castell de Sant Ferran enfront les tropes franceses el dia 27 de novembre de 1794, així com les especulacions que s’originaren a conseqüència d’aquest fet., We review the history of the construction of the castle of Sant-Ferran, near Figueres, that is one of the most important European’s bastioned fortresses. We also summarize the origins of the “Guerra Gran”, the war between the Spanish’s monarchy and the revolutionary France. We present, finally, the main facts and speculations about the “incredible” capitulation of the castle of Sant-Ferran to the French troops the November, 27th of 1794.

En aquest article s’estudien les conseqüències que tingué la Guerra Gran (1793-1795) sobre la població civil de la comarca de l’Empordà, a partir de l’anàlisi de la documentació dels registres parroquials de l’època. S’estudien les partides sagramentals de naixements, matrimonis i òbits esdevinguts en el si de les famílies emigrades o expatriades per motius de la guerra, que s’han conservat registrades en els seus llocs d’acolliment temporal. S’aporten, també, testimonis dels rectors sobre els estralls esdevinguts amb motiu de la invasió de l’exèrcit francès. Insignificants separadament, aquestes anotacions proporcionen una visió de primera mà sobre la magnitud de la tragèdia que visqué la població civil durant aquella contesa armada., In this paper we analyze the documentation from the parish registers in order to study the consequences of the “Guerra Gran” (1793-1795) on the civilian population of the Empordà region. The sacramental registers of births, marriages and deaths, occurring within families migrated or expatriated for reasons of war, which have been preserved registered in their temporary shelter sites, are reported. The witnesses of the rectors about the havoc that occurred during the invasion of the French army are also presented. Although they are insignificant considered separately, these annotations provide a firsthand description about the magnitude of the tragedy suffered by the civilian population during this armed conflict.

En aquest article presentemuns apunts sobre la història de tres entitats que una sèrie d’empordanesos residents a la capital fundaren a Barcelona en els anys de transició del segle XIX al XX: el Centre Empordanès Gracienc (1884), el Centre Empordanès de Barcelona (1891) i l’Ateneu Empordanès de Barcelona (1916). Presentem, també, apunts biogràfics sobre alguns dels homes que les feren possibles: Eusebi Corominas i Cornell, Frederic Viñas i Cusí, Eusebi Fina i Girbau, Joan Vidal i Fraxanet, Eusebi Isern i Dalmau, RamonNoguer i Comet, o el mateix Josep Pella i Forgas. Veurem alguns dels seus actes culturals: concerts, ballades de sardanes, Jocs Florals, homenatges a personalitats empordaneses, edició de llibres, etc., i com aquestes societats, que pretenien ser una mena de “delegació consular” de l’Empordà a Barcelona, jugaren un paper molt important en el desenvolupament del “mite de l’Empordà”., This article presents notes on the history of three societies founded by several people who originally were from the Empordà but resided in Barcelona, in the transition years fromthe nineteenth to the twentieth century: the Centre Empordanès Gracienc (Empordà Circle of –the Barcelona district– Gràcia) founded in 1884, the Centre Empordanès of Barcelona (1891) and the Ateneu (Society) Empordanès of Barcelona (1916). We also present biographical notes on some of the men who made these possible: Eusebi Corominas i Cornell, Frederic Viñas i Cusí, Eusebi Fina i Girbay, Joan Vidal i Fraxanet, Eusebi Isern i Dalmau, Ramon Noguer i Comet or the very Josep Pella i Forgas.We explain some of their cultural activities: concerts, Sardana dances, Jocs Florals (poetry contests), homages to personalities fromthe Empordà, publications, etc. and how these societies, who intended to be a manner of “consulate” or “delegation” of the Empordà in Barcelona, played a very important role in the development of the “myth of the Empordà”.

Els fets de Ribelles fan referència a un incident armat que s’esdevingué a finals del mes de juny del 1841 entre contrabandistes francesos i carrabiners d’hisenda espanyols. L’incident comportà una escalada diplomàtica i el creuament de comunicacions entre la Secretaria d’Estat espanyola i les autoritats franceses. L’estudi d’aquesta documentació ens il·lustra sobre el difícil equilibri que comportava la vida en terra de frontera en el període de transició entre les dues primeres guerres carlines., The “events of Ribelles” refer to an armed incident that involved French smugglers and Spanish customs officers, occurred in late June 1841. The incident motivated a diplomatic appeal to the French authorities fromthe Spanish State Secretary. The study of this documentation has been very useful in order to clarify the difficult equilibriumof everyday life in a small place close to the border during the transition period between the two first Carlist Wars.

L'any 1787 Louis Joseph Proust, professor a l'acadèmia d'artilleria de Segòvia, visità, per ordre del rei, les foneries de bronze de Barcelona i de ferro colat de Sant Sebastià de la Muga (Alt Empordà, Girona) per tal que es familiaritzés amb els processos de química metal·lúrgica a escala industrial. Com a resultat, escrigué una memòria sobre les bales de la Muga amb una sèrie de recomanacions per a la millora de la producció i que ens mostra la dedicació de Proust cap a una «ciència útil»., In 1787 Louis Joseph Proust, professor from the artillery academy of Segovia, was commissioned to visit the bronze foundry of Barcelona and the cast iron foundry of Sant Sebastià de la Muga (Girona), in order to familiarize himself with the industrial applications of metallurgical chemistry. As a result, Proust published a paper about the ammunition of la Muga foundry, including some recommendations to improve the production, a fact which demonstrates Proust’s interest in the application of science to the industrial processes.

L'any 1770 entrà en funcionament prop de la vila de Sant Llorenç de la Muga Alt Empordà) la reial foneria de Sant Sebastià de la Muga, primer alt forn de Catalunya. Per tal de garantir el subministrament de carbó vegetal, els seus responsables proposaren al monarca la declaració d'una reserva d'exclusivitat d'uns 25 km de radi centrada a la foneria i que incloïa gran part de l'actual comarca de l'Alt Empordà i part de la Garrotxa. S'elaborà llavors un mapa detallat de la zona afectada, on s'hi especificaren no únicament els nuclis habitats i les vies de comunicació, sinó també els tipus de boscos, els cultius, tot adjuntant-hi dades numèriques de la població d'animals de granja i d'altra informació econòmicament rellevant. En aquesta comunicació ens centrem, sobretot, en la forma de la representació gràfica del medi natural i humà de l'Empordà, en un mapa únic a la comarca per la seva extensió i detall.

Resumen basado en el de la publicación La reflexión de la luz por un espejo plano es un fenómeno óptico relativamente simple. Sin embargo, la reflexión múltiple por dos o tres espejos (calidoscopio) es un fenómeno sorprendente y cautivador, que permite que la introducción al fascinante mundo de las simetrías matemáticas. Universitat de Barcelona. Biblioteca del Campus de Mundet ; Passeig de la Vall d'Hebron 171; 08035 Barcelona; Tel. +34934021035; Fax +34934021034 ESP

In this communication we review the evolution of blast furnace techniques in Europe in order to place in its historical context the foundation of the royal foundry of Sant Sebastià de la Muga (1768-1794). We justify also the interest of the military estate in promoting the cast iron foundries for ammunition production and the role of the French engineers into the Spanish technical developments in the XVIII century. Finally, we present an original scheme of the main furnace of the royal foundry of Sant Sebastià de la Muga and the chemical analysis of some recovered materials.

We identify those properties of a quantum channel that are relevant for cryptography. We focus on general key distribution protocols that use prepare and measure schemes and the existing classical reconciliation techniques, as these are the protocols feasible with current technology. Given a channel, we derive an easily computable necessary condition of security for such protocols. In spite of its simplicity, this condition is shown to be tight for the Bennett-Brassard 1984 and six-state protocols. We show that the condition becomes also sufficient in the event of a so-called collective attack.

We present a procedure inspired by dense coding, which enables a highly efficient transmission of information of a continuous nature. The procedure requires the sender and the recipient to share a maximally entangled state. We deal with the concrete problem of aligning reference frames or trihedra by means of a quantum system. We find the optimal covariant measurement and compute the corresponding average error, which has a remarkably simple close form. The connection of this procedure with that of estimating unitary transformations on qubits is briefly discussed., 4 pages, RevTeX, Version to appear in PRA

We obtain a simple formula for the average gate fidelity of a linear map acting on qudits. It is given in terms of minimal sets of pure state preparations alone, which may be interesting from the experimental point of view. These preparations can be seen as the outcomes of certain minimal positive operator valued measures. The connection of our results with these generalized measurements is briefly discussed.

We present the optimal scheme for estimating a pure qubit state by means of local measurements on N identical copies. We give explicit examples for low N. For large N, we show that the fidelity saturates the collective measurement bound up to order 1/N. When the signal state lays on a meridian of the Bloch sphere, we show that this can be achieved without classical communication., Version to appear in PRL (minor changes, title changed)

Total spin eigenstates can be used to intrinsically encode a direction, which can later be decoded by means of a quantum measurement. We study the optimal strategy that can be adopted if, as is likely in practical applications, only product states of $N$-spins are available. We obtain the asymptotic behaviour of the average fidelity which provides a proof that the optimal states must be entangled. We also give a prescription for constructing finite measurements for general encoding eigenstates., 4 pages, minor changes, version to appear in PRA

La existencia de un corpus documental de cartas náuticas elaborado en Mallorca entre los siglos XIV y XVI es un hecho indiscutible. La realidad de una escuela cartográfica mallorquina, no obstante, ha sido puesta en cuestión recientemente, a la luz de las nuevas investigaciones historiográficas. En consecuencia, los autores de tales cartas han pasado de ser considerados cientificos a simples ilustradores o decoradores. Un nuevo documento sobre Guillem Soler, de carácter privado, nos hace ver el peligro de interpretaciones demasiado radicales sobre la actividad cartográfica desarrollada en la isla de Mallorca y nos permite plantear algunas nuevas hipótesis sobre la evolución de la misma. It is an unquestionable fact that there is alarge documental corpus of nautical charts elaborated in the island of Mallorca between the XIV and XVI centuries. Nevertheless, some recent historical investigations have questioned the existence of a cartographic school in Mallorca. As a consequence, the authors of such charts have been now considered as simple illustrators or decorators, instead of being considered scientists. A new private document about Guillem Soler points out the danger of the too radical interpretations about the cartographic activity developed in the island of Mallorca and allows us to think about some new hypothesis on the evolution of this activity.

We analyze the problem of sending, in a single transmission, the information required to specify an orthogonal trihedron or reference frame through a quantum channel made out of N elementary spins. We analytically obtain the optimal strategy, i.e., the best encoding state and the best measurement. For large N, we show that the average error goes to zero linearly in 1/N. Finally, we discus the construction of finite optimal measurements., 4 pages