Noise effect on Grover algorithm

The decoherence effect on Grover algorithm has been studied numerically through a noise modelled by a depolarizing channel. Two types of error are introduced characterizing the qubit time evolution and gate application, so the noise is directly related to the quantum network construction. The numerical simulation concludes an exponential damping law for the successive probability of the maxima as time increases. We have obtained an allowed-error law for the algorithm: the error threshold for the allowed noise behaves as Eth(N) ~ 1/N1.1 (N being the size of the data set). As the power of N is almost one, we consider the Grover algorithm as robust to a certain extent against decoherence. This law also provides an absolute threshold: if the free evolution error is greater than 0.043, Grover algorithm does not work for any number of qubits affected by the present error model. The improvement in the probability of success, in the case of two qubits has been illustrated by using a fault-tolerant encoding of the initial state by means of the [[7,1,3]] quantum code.Comment: Accepted to be published in Eur. Phys. J. D (2008

Equilibria and Dynamics of two coupled chains of interacting dipoles

We explore the energy transfer dynamics in an array of two chains of identical rigid interacting dipoles. A crossover between two different ground state (GS) equilibrium configurations is observed with varying distance between the two chains of the array. Linearizing around the GS configurations, we verify that interactions up to third nearest neighbors should be accounted for accurately describe the resulting dynamics. Starting with one of the GS, we excite the system by supplying it with an excess energy DK located initially on one of the dipoles. We study the time evolution of the array for different values of the system parameters b and DK. Our focus is hereby on two features of the energy propagation: the redistribution of the excess energy DK among the two chains and the energy localization along each chain. For typical parameter values, the array of dipoles reaches both the equipartition between the chains and the thermal equilibrium from the early stages of the time evolution. Nevertheless, there is a region in parameter space (b,DK) where even up to the long computation time of this study, the array does neither reach energy equipartition nor thermalization between chains. This fact is due to the existence of persistent chaotic breathers

Chaos and thermalization in a classical chain of dipoles

M.I. and J.P.S. acknowledge financial support by the 560FQ Spanish Project No. MTM2017-88137-C2-2-P (MINECO). R.G.F. gratefully acknowledges financial support by the Spanish projects PID2020-113390GB-I00 (MICIN), PY20-00082 (Junta de Andalucía) and A-FQM-52-UGR20 (ERDF-University of Granada), and the Andalusian Research Group FQM-207. These work used the Beronia cluster (Universidad de La Rioja), which is supported by FEDERMINECO Grant No. UNLR-094E-2C-225.We explore the connection between chaos, thermalization, and ergodicity in a linear chain of N interacting dipoles. Starting from the ground state, and considering chains of different numbers of dipoles, we introduce single site excitations with excess energy ΔK. The time evolution of the chaoticity of the system and the energy localization along the chain is analyzed by computing, up to a very long time, the statistical average of the finite-time Lyapunov exponent λ(t) and the participation ratio Π(t). For small ΔK, the evolution of λ(t) and Π(t) indicates that the system becomes chaotic at approximately the same time as Π(t) reaches a steady state. For the largest considered values of ΔK the system becomes chaotic at an extremely early stage in comparison with the energy relaxation times. We find that this fact is due to the presence of chaotic breathers that keep the system far from equipartition and ergodicity. Finally, we show numerically and analytically that the asymptotic values attained by the participation ratio Π(t) fairly correspond to thermal equilibrium.Andalusian Research Group FQM-207ERDF-University of GranadaFEDER-MINECO UNLR-094E-2C-225Ministerio de Economía y Competitividad PID2020-113390GB-I00, PY20-00082Junta de Andalucía A-FQM-52-UGR2

El Caso de Ganemos Zaragoza: Una aproximación desde la sociología relacional

En este artículo se presentan los resultados de una investigación que ha analizado la génesis del movimiento Ganemos Zaragoza/Zaragoza en Común (GZ/ZeC) y el paso a su constitución como formación política. A partir del análisis de los datos de una encuesta (n=253) y entrevistas a informantes clave, mostramos que los movimientos sociales (entendidos como una nueva red social) nacen en situaciones sociales “enredadas”. Para alcanzar tal fin, nos situamos en la mirada teórica de los movimientos sociales desde una perspectiva relacional. Entre sus principales resultados se ha podido comprobar cómo GZ/ZeC se tejió, en un primer momento, a través de los contactos y alianzas que se establecieron entre movimientos sociales preexistentes, que terminaron por construir la malla relacional desde la que se fue edificando y fortaleciendo el movimiento. Por tanto, este texto sirve para comprender el proceso de configuración de las candidaturas de confluencias municipales en las elecciones de mayo de 2015. This article presents the results of research related to analyzing the genesis of the Ganemos Zaragoza / Zaragoza in Common (GZ/ZeC) movement and its passage to constituting a political formation. Through an analysis of a survey data (n=253) and key informant interviews, we show that social movements (understood as a new social network) are born in “convoluted” social situations. To achieve this goal, we look at the theoretical view of social movements from a relational perspective. Among the main results we can see how GZ/ZeC was formed, at first, through contacts and partnerships established between preexisting social movements, that eventually ended up gaining relational support from which the movement was built and strengthened. Therefore, this text serves to understand how the process was set up for candidates in the municipal elections of May 2015

Advanced synthesis of conductive polyaniline using laccase as biocatalyst

18 p.-7 fig.-1 tab.Polyaniline is a conductive polymer with distinctive optical and electrical properties. Its enzymatic synthesis is an environmentally friendly alternative to the use of harsh oxidants and extremely acidic conditions. 7D5L, a high-redox potential laccase developed in our lab, is the biocatalyst of choice for the synthesis of green polyaniline (emeraldine salt) due to its superior ability to oxidize aniline and kinetic stability at the required polymerization conditions (pH 3 and presence of anionic surfactants) as compared with other fungal laccases.Doses as low as 7.6 nM of 7D5L catalyze the polymerization of 15 mM aniline (in 24 h, room temperature, 7% yield) in the presence of different anionic surfactants used as doping templates to provide linear and water-soluble polymers. Aniline polymerization was monitored by the increase of the polaron absorption band at 800 nm (typical for emeraldine salt). Best polymerization results were obtained with 5 mM sodium dodecylbenzenesulfonate (SDBS) as template. At fixed conditions (15 mM aniline and 5mM SDBS), polymerization rates obtained with 7D5L were 2.5-fold the rates obtained with commercial Trametes villosa laccase. Moreover, polyaniline yield was notably boosted to 75% by rising 7D5L amount to 0.15 μM, obtaining 1g of green polyaniline in 1L-reaction volume. The green polymer obtained with the selected system (7D5L/SDBS) holds excellent electrochemical and electro-conductive properties displayed in water-dispersible nanofibers,which is advantageous for the nanomaterial to be readily cast into uniform films for different applications.This work was funded by INDOX (KBBE-2013-7-613549) European project and NOESIS (BIO2014-56388-R) Spanish national project.Peer reviewe