Reply to Comment on "A local realist model for correlations of the singlet state"

The general conclusion of Seevinck and Larsson is that our model exploits the so-called coincidence-time loophole and produces sinusoidal (quantum-like) correlations but does not model the singlet state because it does not violate the relevant Bell inequality derived by Larsson and Gill, since in order to obtain the sinusoidal correlations the probability of coincidences in our model goes to zero. In this reply, we refute their arguments that lead to this conclusion and demonstrate that our model can reproduce results of photon and ion-trap experiments with frequencies of coincidences that are not in conflict with the observations.Comment: Corrected typo

Energy Fluctuations in One Dimensional Classical Magnets

The time- and frequency dependent energy fluctuations in the Heisenberg chain are studied by means of a continued fraction representation. In a broad wave vector and temperature range, the energy fluctuations are found to display dominant oscillatory behavior.

Simulation of Quantum Computation: A deterministic event-based approach

We demonstrate that locally connected networks of machines that have primitive learning capabilities can be used to perform a deterministic, event-based simulation of quantum computation. We present simulation results for basic quantum operations such as the Hadamard and the controlled-NOT gate, and for seven-qubit quantum networks that implement Shor's numbering factoring algorithm.Comment: J. Comp. Theor. Nanoscience (in press); http://www.compphys.net/dl

Event-based simulation of single-photon beam splitters and Mach-Zehnder interferometers

We demonstrate that networks of locally connected processing units with a primitive learning capability exhibit behavior that is usually only attributed to quantum systems. We describe networks that simulate single-photon beam-splitter and Mach-Zehnder interferometer experiments on a causal, event-by-event basis and demonstrate that the simulation results are in excellent agreement with quantum theory.Comment: EuroPhys. Lett. (in press); http://www.compphys.net/dl

Event-by-event simulation of quantum phenomena

In this talk, I discuss recent progress in the development of simulation algorithms that do not rely on any concept of quantum theory but are nevertheless capable of reproducing the averages computed from quantum theory through an event-by-event simulation. The simulation approach is illustrated by applications to single-photon Mach-Zehnder interferometer experiments and Einstein-Podolsky-Rosen-Bohm experiments with photons.Comment: V Brazilian Meeting on Simulational Physics, Ouro Preto, 200

Efficient data processing and quantum phenomena: Single-particle systems

We study the relation between the acquisition and analysis of data and quantum theory using a probabilistic and deterministic model for photon polarizers. We introduce criteria for efficient processing of data and then use these criteria to demonstrate that efficient processing of the data contained in single events is equivalent to the observation that Malus' law holds. A strictly deterministic process that also yields Malus' law is analyzed in detail. We present a performance analysis of the probabilistic and deterministic model of the photon polarizer. The latter is an adaptive dynamical system that has primitive learning capabilities. This additional feature has recently been shown to be sufficient to perform event-by-event simulations of interference phenomena, without using concepts of wave mechanics. We illustrate this by presenting results for a system of two chained Mach-Zehnder interferometers, suggesting that systems that perform efficient data processing and have learning capability are able to exhibit behavior that is usually attributed to quantum systems only.Comment: http://www.compphys.net/dl

Massive Parallel Quantum Computer Simulator

We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.Comment: To appear in Comp. Phys. Com

Event-based computer simulation model of Aspect-type experiments strictly satisfying Einstein's locality conditions

Inspired by Einstein-Podolsky-Rosen-Bohm experiments with photons, we construct an event-based simulation model in which every essential element in the ideal experiment has a counterpart. The model satisfies Einstein's criteria of local causality and does not rely on concepts of quantum and probability theory. We consider experiments in which the averages correspond to those of a singlet and product state of a system of two $S=1/2$ particles. The data is analyzed according to the experimental procedure, employing a time window to identify pairs. We study how the time window and the passage time of the photons, which depends on the relative angle between their polarization and the polarizer's direction, influences the correlations, demonstrating that the properties of the optical elements in the observation stations affect the correlations although the stations are separated spatially and temporarily. We show that the model can reproduce results which are considered to be intrinsically quantum mechanical

Understanding vulnerability for depression from a cognitive neuroscience perspective: a reappraisal of attentional factors and a new conceptual framework

We propose a framework to understand increases in vulnerability for depression after recurrent episodes that links attention processes and schema activation to negative mood states, by integrating cognitive and neurobiological findings. Depression is characterized by a mood-congruent attentional bias at later stages of information processing. The basic idea of our framework is that decreased activity in prefrontal areas, mediated by the serotonin metabolism which the HPA axis controls, is associated with an impaired attenuation of subcortical regions, resulting in prolonged activation of the amygdala in response to stressors in the environment. Reduced prefrontal control in interaction with depressogenic schemas leads to impaired ability to exert attentional inhibitory control over negative elaborative processes such as rumination, leading in turn to sustained negative affect. These elaborative processes are triggered by the activation of negative schemas after confrontation with stressors. In our framework, attentional impairments are postulated as a crucial process in explaining the increasing vulnerability after depressive episodes, linking cognitive and biological vulnerability factors. We review the empirical data on the biological factors associated with the attentional impairments and detail how they are associated with rumination and mood regulation. The aim of our framework is to stimulate translational research

Event-based simulation of quantum physics experiments

We review an event-based simulation approach which reproduces the statistical distributions of wave theory not by requiring the knowledge of the solution of the wave equation of the whole system but by generating detection events one-by-one according to an unknown distribution. We illustrate its applicability to various single photon and single neutron interferometry experiments and to two Bell test experiments, a single-photon Einstein-Podolsky-Rosen experiment employing post-selection for photon pair identification and a single-neutron Bell test interferometry experiment with nearly $100\%$ detection efficiency.Comment: Lectures notes of the Advanced School on Quantum Foundations and Open Quantum Systems, Jo\~ao Pessoa, Brazil, July 2012, edited by T. M. Nieuwenhuizen et al, World Scientific, to appea