Home About us Contact
|
Home About us Contact | ||
|
|
||
Quantum Physics (quantum + physics)
Selected AbstractsIntroductory quantum physics courses using a LabVIEW multimedia moduleCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2007Ismael Orquín Abstract We present the development of a LabVIEW multimedia module for introductory Quantum Physics courses and our experience in the use of this application as an educational tool in learning methodologies. The program solves the time-dependent Schrödinger equation (TDSE) for arbitrary potentials. We describe the numerical method used for solving this equation, as well as some mathematical tools employed to reduce the calculation time and to obtain more accurate results. As an illustration, we present the evolution of a wave packet for three different potentials: the repulsive barrier potential, the repulsive step potential, and the harmonic oscillator. This application has been successfully integrated in the learning strategies of the course Quantum Physics for Engineering at the Polytechnic University of Valencia, Spain. © 2007 Wiley Periodicals, Inc. Comput Appl Eng Educ. 15: 124,133, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20100 [source] Free space quantum key distribution: Towards a real life applicationFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 8-10 2006H. Weier Abstract Quantum key distribution (QKD) [1] is the first method of quantum information science that will find its way into our everyday life. It employs fundamental laws of quantum physics to ensure provably secure symmetric key generation between two parties. The key can then be used to encrypt and decrypt sensitive data with unconditional security. Here, we report on a free space QKD implementation using strongly attenuated laser pulses over a distance of 480 m. It is designed to work continuously without human interaction. Until now, it produces quantum keys unattended at night for more than 12 hours with a sifted key rate of more than 50 kbit/s and a quantum bit error rate between 3% and 5%. [source] Time asymmetric quantum theory , I. Modifying an axiom of quantum physicsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 6 2003A.R. Bohm A slight modification of one axiom of quantum theory changes a reversible theory into a time asymmetric theory. Whereas the standard Hilbert space axiom does not distinguish mathematically between the space of states (in-states of scattering theory) and the space of observables (out-"states" of scattering theory) the new axiom associates states and observables to two different Hardy subspaces which are dense in the same Hilbert space and analytic in the lower and upper complex energy plane, respectively. As a consequence of this new axiom the dynamical equations (Schrödinger or Heisenberg) integrate to a semigroup evolution. Extending this new Hardy space axiom to a relativistic theory provides a relativistic theory of resonance scattering and decay with Born probablilities that fulfill Einstein causality and the exponential decay law. [source] Time asymmetric quantum theory , III.FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 6 2003Decaying states, the causal Poincaré semigroup Abstract These Gamow kets span an irreducible representation space for Poincaré transformations which, similar to the Wigner representations for stable particles, are characterized by spin (angular momentum of the partial wave amplitude) and complex mass (position of the resonance pole). The Poincaré transformations of the Gamow kets, as well as of the Lippmann-Schwinger plane wave scattering states, form only a semigroup of Poincaré transformations into the forward light cone. Their transformation properties are derived. From these one obtains an unambiguous definition of resonance mass and width for relativistic resonances. The physical interpretation of these transformations for the Born probabilities and the problem of causality in relativistic quantum physics is discussed. [source] MONTE CARLO SIMULATION OF FAR INFRARED RADIATION HEAT TRANSFER: THEORETICAL APPROACHJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2006F. TANAKA ABSTRACT We developed radiation heat transfer models with the combination of the Monte Carlo (MC) method and computational fluid dynamic approach and two-dimensional heat transfer models based on the fundamental quantum physics of radiation and fluid dynamics. We investigated far infrared radiation (FIR) heating in laminar and buoyancy airflow. A simple prediction model in laminar airflow was tested with an analytical solution and commercial software (CFX 4). The adequate number of photon tracks for MC simulation was established. As for the complex designs model, the predicted results agreed well with the experimental data with root mean square error of 3.8 K. Because food safety public concerns are increasing, we applied this model to the prediction of the thermal inactivation level by coupling with the microbial kinetics model. Under buoyancy airflow condition, uniformity of FIR heating was improved by selecting adequate wall temperature and emissivity. [source] Notes on theory and experimental conditions behind two-photon excitation microscopyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2004Alessandro Esposito Abstract This report deals with the fundamental quantum physics behind two-photon excitation also providing a link to the experimental consequences exploited in microscopy. The optical sectioning effect is demonstrated as well as the distribution of excitation and of fluorescence emission. Microsc. Res. Tech. 63:12,17, 2004. © 2003 Wiley-Liss, Inc. [source] A practical method for computing the largest M -eigenvalue of a fourth-order partially symmetric tensorNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 7 2009Yiju Wang Abstract In this paper, we consider a bi-quadratic homogeneous polynomial optimization problem over two unit spheres arising in nonlinear elastic material analysis and in entanglement studies in quantum physics. The problem is equivalent to computing the largest M -eigenvalue of a fourth-order tensor. To solve the problem, we propose a practical method whose validity is guaranteed theoretically. To make the sequence generated by the method converge to a good solution of the problem, we also develop an initialization scheme. The given numerical experiments show the effectiveness of the proposed method. Copyright © 2009 John Wiley & Sons, Ltd. [source] On large-scale diagonalization techniques for the Anderson model of localizationPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2007Olaf Schenk We propose efficient preconditioning algorithms for an eigenvalue problem arising in quantum physics, namely the computation of a few interior eigenvalues and their associated eigenvectors for large-scale sparse real and symmetric indefinite matrices of the Anderson model of localization. Our preconditioning approaches for the shift-and-invert symmetric indefinite linear system are based on maximum weighted matchings and algebraic multi-level incomplete LDLT factorizations. These techniques can be seen as a complement to the alternative idea of using more complete pivoting techniques for the highly ill-conditioned symmetric indefinite Anderson matrices. Our numerical examples reveal that recent algebraic multi-level preconditioning solvers can accelerate the computation of a large-scale eigenvalue problem corresponding to the Anderson model of localization by several orders of magnitude. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Probabilistic observables, conditional correlations, and quantum physicsANNALEN DER PHYSIK, Issue 7 2010C. Wetterich Abstract We discuss the classical statistics of isolated subsystems. Only a small part of the information contained in the classical probability distribution for the subsystem and its environment is available for the description of the isolated subsystem. The "coarse graining of the information" to micro-states implies probabilistic observables. For two-level probabilistic observables only a probability for finding the values one or minus one can be given for any micro-state, while such observables could be realized as classical observables with sharp values on a substate level. For a continuous family of micro-states parameterized by a sphere all the quantum mechanical laws for a two-state system follow under the assumption that the purity of the ensemble is conserved by the time evolution. The correlation functions of quantum mechanics correspond to the use of conditional correlation functions in classical statistics. We further discuss the classical statistical realization of entanglement within a system corresponding to four-state quantum mechanics. We conclude that quantum mechanics can be derived from a classical statistical setting with infinitely many micro-states. [source] Oszillierende Weltmodelle versus Urknallmodelle.BERICHTE ZUR WISSENSCHAFTSGESCHICHTE, Issue 4 2004Das oszillierende Weltmodell Friedmanns, die Ablehnung der Anfangssingularität durch russische Kosmologen und die Zustimmung der katholischen Kirche zur Urknalltheorie Lemaîtres und Hawkings Abstract The Russian mathematician and physicist Friedmann and the Belgian priest and physicist Lemaître were the first to consider non-static world models in the framework of Einstein's general theory of relativity. Friedmann seemed to favour a periodic, oscillating cosmological model. His investigations were taken up by Russian cosmologists in the 1960s. They stated that the singularities present in many of the Friedmann-Lemaître cosmological models seemed to be artificial and were ascribed to the assumption of a highly symmetric distribution of cosmic matter. Their disapproval of singularities seems to be in accord with Soviet ideological requirements during that time like atheism and dialectic materialism. They had to retract their statements after Hawking had proved his singularity theorems and after the microwave background had been discovered. Hawking followed the line of thought which was initiated by Lemaître in the early 1930s. Lemaître had combined for the first time quantum physics and relativistic cosmology and had developed his idea of the primeval atom, a beginning of the universe in a dense state with just one quantum containing the whole mass of the universe. Pope Pius XII brought together this primeval atom and God as the Creator of the universe and declared in 1951 that big bang cosmology is compatible with the Bible. Not surprisingly Hawking was awarded the Pius XI medal by the Vatican in 1975 for his contributions to big bang cosmology. [source] Can we use diffusion MRI as a bio-marker of neurodegenerative processes?BIOESSAYS, Issue 11-12 2008Yaniv Assaf Magnetic resonance imaging (MRI) is an imaging technique with a rapidly expanding application range. This methodology, which relies on quantum physics and substance magnetic properties, is now being routinely used in the clinics and medical research. With the advent of measuring functional brain activity with MRI (functional MRI), this methodology has reached a larger section of the neuroscience community (e.g. psychologists, neurobiologists). In the past, the use of MRI as a biomarker or as an assay to probe tissue pathophysiological condition was limited. However, with the new applications of MRI: molecular imaging, contrast-enhanced imaging and diffusion imaging, MRI is turning into a powerful tool for in vivo characterization of tissue pathophysiology. This review focuses on the diffusion MRI. Although it only measures the averaged Brownian translational motion of water molecules, using different analysis schemes, one can extract a wide range of quantitative indices that represent tissue morphology and compartmentalization. Statistical and visualization routines help to relate these indices to biologically relevant measures such as cell density, water content and size distribution. The aim of this review is to shed light on the potential of this methodology to be used in biological research. To that end, this review is intended for the non-MRI specialists who wish to pursue biological research with this methodology. We will overview the current applications of diffusion MRI and its relation to cellular biology of brain tissue. BioEssays 30:1235,1245, 2008. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||||||||