Quantum games via search algorithms

We build new quantum games, similar to the spin flip game, where as a novelty the players perform measurements on a quantum system associated to a continuous time search algorithm. The measurements collapse the wave function into one of the two possible states. These games are characterized by a continuous space of strategies and the selection of a particular strategy is determined by the moments when the players measure.Comment: 4 pages, 3 figure

Hilbert Space Average Method and adiabatic quantum search

We discuss some aspects related to the so-called Hilbert space Average Method, as an alternative to describe the dynamics of open quantum systems. First we present a derivation of the method which does not make use of the algebra satisfied by the operators involved in the dynamics, and extend the method to systems subject to a Hamiltonian that changes with time. Next we examine the performance of the adiabatic quantum search algorithm with a particular model for the environment. We relate our results to the criteria discussed in the literature for the validity of the above-mentioned method for similar environments.Comment: 6 pages, 1 figur

Simulation of the elementary evolution operator with the motional states of an ion in an anharmonic trap

Following a recent proposal of L. Wang and D. Babikov, J. Chem. Phys. 137, 064301 (2012), we theoretically illustrate the possibility of using the motional states of a $Cd^+$ ion trapped in a slightly anharmonic potential to simulate the single-particle time-dependent Schr\"odinger equation. The simulated wave packet is discretized on a spatial grid and the grid points are mapped on the ion motional states which define the qubit network. The localization probability at each grid point is obtained from the population in the corresponding motional state. The quantum gate is the elementary evolution operator corresponding to the time-dependent Schr\"odinger equation of the simulated system. The corresponding matrix can be estimated by any numerical algorithm. The radio-frequency field able to drive this unitary transformation among the qubit states of the ion is obtained by multi-target optimal control theory. The ion is assumed to be cooled in the ground motional state and the preliminary step consists in initializing the qubits with the amplitudes of the initial simulated wave packet. The time evolution of the localization probability at the grids points is then obtained by successive applications of the gate and reading out the motional state population. The gate field is always identical for a given simulated potential, only the field preparing the initial wave packet has to be optimized for different simulations. We check the stability of the simulation against decoherence due to fluctuating electric fields in the trap electrodes by applying dissipative Lindblad dynamics.Comment: 31 pages, 8 figures. Revised version. New title, new figure and new reference

Sub-ballistic behavior in quantum systems with L\'evy noise

We investigate the quantum walk and the quantum kicked rotor in resonance subjected to noise with a L\'evy waiting time distribution. We find that both systems have a sub-ballistic wave function spreading as shown by a power-law tail of the standard deviation.Comment: 4 pages, 4 figure

Estudio comparativo de la influencia de la atención y concentración en los métodos: personalizado, montessoriano y formal en niños de tercer grado

Trabajo final de graduación de 183 páginas en formato pdfLos niños con necesidades educativas especiales son cada día más comunes dentro del sistema educativo regular. En el artículo del periódico La Nación del 21 de noviembre del 2005, titulado: “Adecuaciones curriculares se duplicaron en los últimos cinco años” se comenta que el 10% de los estudiantes escolares y colegiales requieren de algún ajuste en su programa. Según el folleto Lineamientos para el trabajo de los Comité de apoyo o educativo del Ministerio de Educación Pública (2004) señala: Las adecuaciones curriculares son apoyos educativos que las docentes de escuelas y colegios brindan a los estudiantes que los necesitan. Responden a las formas individuales de aprender de los estudiantes, por lo tanto no se aplican como recetas en el aula, sino que se hace pensando y respondiendo a las necesidades de cada uno de ellos. (p. 3). Las necesidades educativas especiales plantean que la educación debe responder a la diversidad del alumnado. La mayoría de estos niños requieren de un diagnóstico temprano de sus problemas y un tratamiento integral y transdiciplinario. De acuerdo con García (2000): ...el profesor no debe profundizar en el déficit, sino más bien en las posibilidades del alumno, la identificación de las necesidades educativas especiales de un alumno se convierten en el inicio de la discriminación de las actuaciones educativas apropiadas, de los recursos personales y materiales, a partir de subrayar sus capacidades sin perder de vista sus limitaciones. (p.12). 3 La identificación temprana de estas necesidades hace posible prevenir el fracaso escolar, la deserción o frustración, además de consecuencias adversas en su autoestima. Por esta razón, se deben unificar esfuerzos por parte de los educadores en la búsqueda de soluciones más efectivas que contribuyan a mejorar o al menos, disminuir los efectos adversos en el desenvolvimiento pleno de las capacidades de los alumnos que presentan este diagnóstico.Universidad Estatal a Distancia de Costa Ric

Quantum random walk on the line as a markovian process

We analyze in detail the discrete--time quantum walk on the line by separating the quantum evolution equation into Markovian and interference terms. As a result of this separation, it is possible to show analytically that the quadratic increase in the variance of the quantum walker's position with time is a direct consequence of the coherence of the quantum evolution. If the evolution is decoherent, as in the classical case, the variance is shown to increase linearly with time, as expected. Furthermore we show that this system has an evolution operator analogous to that of a resonant quantum kicked rotor. As this rotator may be described through a quantum computational algorithm, one may employ this algorithm to describe the time evolution of the quantum walker.Comment: few typos corrected, 13 pages, 2 figures, to appear in Physica

Topological Insulators with Inversion Symmetry

Topological insulators are materials with a bulk excitation gap generated by the spin orbit interaction, and which are different from conventional insulators. This distinction is characterized by Z_2 topological invariants, which characterize the groundstate. In two dimensions there is a single Z_2 invariant which distinguishes the ordinary insulator from the quantum spin Hall phase. In three dimensions there are four Z_2 invariants, which distinguish the ordinary insulator from "weak" and "strong" topological insulators. These phases are characterized by the presence of gapless surface (or edge) states. In the 2D quantum spin Hall phase and the 3D strong topological insulator these states are robust and are insensitive to weak disorder and interactions. In this paper we show that the presence of inversion symmetry greatly simplifies the problem of evaluating the Z_2 invariants. We show that the invariants can be determined from the knowledge of the parity of the occupied Bloch wavefunctions at the time reversal invariant points in the Brillouin zone. Using this approach, we predict a number of specific materials are strong topological insulators, including the semiconducting alloy Bi_{1-x} Sb_x as well as \alpha-Sn and HgTe under uniaxial strain. This paper also includes an expanded discussion of our formulation of the topological insulators in both two and three dimensions, as well as implications for experiments.Comment: 16 pages, 7 figures; published versio

Internet-delivered cognitive-behaviour therapy (ICBT) for obsessive-compulsive disorder when delivered as routine clinical care: A phase IV clinical trial

Cognitive-behaviour therapy (CBT) is an effective treatment for obsessive-compulsive disorder (OCD), but many patients experience difficulty accessing this treatment. Internet-delivered CBT (ICBT) enhances access to CBT for individuals with OCD and has been shown to be efficacious in Phase I, II, and III clinical trials. However, there are fewer studies investigating ICBT for OCD in Phase IV clinical trials, which demonstrate the effectiveness of the intervention when provided as part of routine care. The aim of the present study was to report on the effectiveness of ICBT for OCD, using data from Australia’s MindSpot Clinic, a federally funded treatment service that provides free ICBT to Australian adults with anxiety, depression, and pain conditions. A total of 225 MindSpot users (68 % female; Mage = 34.82; SD = 11.02) were included in the study. Within-group effect sizes at post-treatment on the Yale-Brown Obsessive-Compulsive Scale, indicated medium effect sizes (g = 0.6; 95 % CI: 0.5−0.7), increasing to large effects at three-month follow up (g = 0.9; 95 % CI: 0.8–1.0). Effects on secondary outcome measures including measures of depression, generalized anxiety, and psychological distress ranged from (g = 0.5–0.6) at post-treatment and (g = 0.5–0.7) at three-month follow up. Results from benchmarking analyses indicated that the results from routine care were significantly smaller than those found in a recent clinical trial using the same treatment protocol. The results indicate that ICBT delivered in real world settings is associated with meaningful improvements in OCD symptoms, however future research may wish to examine which patients respond best to this treatment approach and how to enhance outcomes

Treating anxiety and depression in older adults: Randomised controlled trial comparing guided V. Self-guided internet-delivered cognitive-behavioural therapy

© 2016 The Royal College of Psychiatrists. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence. Background Symptoms of anxiety and depression are prevalent in older adults. Aims To compare clinician-guided and self-guided versions of a transdiagnostic internet-delivered cognitive-behavioural therapy (iCBT) intervention for adults aged 60 years and above. Method Adults (n=433) with symptoms of anxiety and depression were randomly allocated to: (1) clinician-guided treatment (n=153); (2) initial clinician interview followed by self-guided treatment (n=140); or (3) self-guided treatment without interview (n=140). Results Large reductions (d ≥1.00) in symptoms of depression and anxiety were observed across groups, and sustained at follow-up. No differences were observed in clinical outcomes or satisfaction ratings. Age did not affect outcomes. Conclusions Carefully developed iCBT interventions may significantly reduce symptoms of anxiety and depression in older adults when delivered in either clinician-guided or self-guided formats