WorldWideScience

Sample records for quantum mechanical studies

  1. Quantum Mechanical Studies of DNA and LNA

    DEFF Research Database (Denmark)

    Koch, Troels; Shim, Irene; Lindow, Morten

    2014-01-01

    Quantum mechanical (QM) methodology has been employed to study the structure activity relations of DNA and locked nucleic acid (LNA). The QM calculations provide the basis for construction of molecular structure and electrostatic surface potentials from molecular orbitals. The topologies of the e......Quantum mechanical (QM) methodology has been employed to study the structure activity relations of DNA and locked nucleic acid (LNA). The QM calculations provide the basis for construction of molecular structure and electrostatic surface potentials from molecular orbitals. The topologies...

  2. Quantum mechanics

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    The book is on quantum mechanics. The emphasis is on the basic concepts and the methodology. The chapters include: Breakdown of classical concepts; Quantum mechanical concepts; Basic postulates of quantum mechanics; solution of problems in quantum mechanics; Simple harmonic oscillator; and Angular Momentum

  3. Quantum Mechanical Study of Atoms and Molecules

    Science.gov (United States)

    Sahni, R. C.

    1961-01-01

    This paper, following a brief introduction, is divided into five parts. Part I outlines the theory of the molecular orbital method for the ground, ionized and excited states of molecules. Part II gives a brief summary of the interaction integrals and their tabulation. Part III outlines an automatic program designed for the computation of various states of molecules. Part IV gives examples of the study of ground, ionized and excited states of CO, BH and N2 where the program of automatic computation and molecular integrals have been utilized. Part V enlists some special problems of Molecular Quantum Mechanics are being tackled at New York University.

  4. Quantum Mechanical Study of Nanoscale MOSFET

    Science.gov (United States)

    Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan

    2001-01-01

    The steady state characteristics of MOSFETS that are of practical Interest are the drive current, off-current, dope of drain current versus drain voltage, and threshold voltage. In this section, we show that quantum mechanical simulations yield significantly different results from drift-diffusion based methods. These differences arise because of the following quantum mechanical features: (I) polysilicon gate depletion in a manner opposite to the classical case (II) dependence of the resonant levels in the channel on the gate voltage, (III) tunneling of charge across the gate oxide and from source to drain, (IV) quasi-ballistic flow of electrons. Conclusions dI/dV versus V does not increase in a manner commensurate with the increase in number of subbands. - The increase in dI/dV with bias is much smaller then the increase in the number of subbands - a consequence of bragg reflection. Our calculations show an increase in transmission with length of contact, as seen in experiments. It is desirable for molecular electronics applications to have a small contact area, yet large coupling. In this case, the circumferential dependence of the nanotube wave function dictates: - Transmission in armchair tubes saturates around unity - Transmission in zigzag tubes saturates at two.

  5. Quantum mechanical studies of complex ferroelectric perovskites

    Science.gov (United States)

    Ramer, Nicholas John

    In many electronic device applications, there is a need to interconvert electrical energy and other types of energy. Ferroelectric materials, which possess a voltage-dependent polarization, can enable this energy conversion process. Because of the broad interest in ferroelectric materials for these devices, there is a critical research effort, both experimental and theoretical, to understand these materials and aid in the development of materials with improved properties. This thesis presents detailed quantum mechanical investigations of the behavior of a complex ferroelectric perovskite under applied stress. In particular, we have chosen to study the solid solution PbZr1-xTix O3 (PZT). Since the study of ferroelectricity involves understanding both its structural and electronic signatures in materials, it has necessitated the development of a novel theoretical technique which improves the accuracy of the pseudopotentials used in our density functional theory calculations as well as a new method for constructing three-dimensional atomistic responses to small amounts of external stress. To examine the material's behavior under larger amounts of stress, we have studied the behavior of a composition of PZT lying near a structural phase boundary. On either side of the phase boundary, the material is characterized by a different polarization direction and may easily be switched between phases by applying external stress. In addition to stress-induced phase transitions, most ferroelectric materials also have composition dependent phase boundaries. Since different compositions of PZT would require increased computational effort, we have formulated an improved virtual crystal approach that makes tractable the study of the entire composition range. Using this method, we have been able to show for the first time via first-principles calculations, a composition dependent phase transition in a ferroelectric material. This thesis has accomplished three important goals: new

  6. Quantum mechanics

    CERN Document Server

    Rae, Alastair I M

    2016-01-01

    A Thorough Update of One of the Most Highly Regarded Textbooks on Quantum Mechanics Continuing to offer an exceptionally clear, up-to-date treatment of the subject, Quantum Mechanics, Sixth Edition explains the concepts of quantum mechanics for undergraduate students in physics and related disciplines and provides the foundation necessary for other specialized courses. This sixth edition builds on its highly praised predecessors to make the text even more accessible to a wider audience. It is now divided into five parts that separately cover broad topics suitable for any general course on quantum mechanics. New to the Sixth Edition * Three chapters that review prerequisite physics and mathematics, laying out the notation, formalism, and physical basis necessary for the rest of the book * Short descriptions of numerous applications relevant to the physics discussed, giving students a brief look at what quantum mechanics has made possible industrially and scientifically * Additional end-of-chapter problems with...

  7. Quantum mechanics

    CERN Document Server

    Powell, John L

    2015-01-01

    Suitable for advanced undergraduates, this thorough text focuses on the role of symmetry operations and the essentially algebraic structure of quantum-mechanical theory. Based on courses in quantum mechanics taught by the authors, the treatment provides numerous problems that require applications of theory and serve to supplement the textual material.Starting with a historical introduction to the origins of quantum theory, the book advances to discussions of the foundations of wave mechanics, wave packets and the uncertainty principle, and an examination of the Schrödinger equation that includ

  8. Quantum mechanics

    International Nuclear Information System (INIS)

    Rae, A.I.M.

    1981-01-01

    This book, based on a thirty lecture course given to students at the beginning of their second year, covers the quantum mechanics required by physics undergraduates. Early chapters deal with wave mechanics, including a discussion of the energy states of the hydrogen atom. These are followed by a more formal development of the theory, leading to a discussion of some advanced applications and an introduction to the conceptual problems associated with quantum measurement theory. Emphasis is placed on the fundamentals of quantum mechanics. Problems are included at the end of each chapter. (U.K.)

  9. Quantum mechanics

    International Nuclear Information System (INIS)

    Basdevant, J.L.; Dalibard, J.; Joffre, M.

    2008-01-01

    All physics is quantum from elementary particles to stars and to the big-bang via semi-conductors and chemistry. This theory is very subtle and we are not able to explain it without the help of mathematic tools. This book presents the principles of quantum mechanics and describes its mathematical formalism (wave function, Schroedinger equation, quantum operators, spin, Hamiltonians, collisions,..). We find numerous applications in the fields of new technologies (maser, quantum computer, cryptography,..) and in astrophysics. A series of about 90 exercises with their answers is included. This book is based on a physics course at a graduate level. (A.C.)

  10. Quantum mechanics

    CERN Document Server

    Fitzpatrick, Richard

    2015-01-01

    Quantum mechanics was developed during the first few decades of the twentieth century via a series of inspired guesses made by various physicists, including Planck, Einstein, Bohr, Schroedinger, Heisenberg, Pauli, and Dirac. All these scientists were trying to construct a self-consistent theory of microscopic dynamics that was compatible with experimental observations. The purpose of this book is to present quantum mechanics in a clear, concise, and systematic fashion, starting from the fundamental postulates, and developing the theory in as logical manner as possible. Topics covered in the book include the fundamental postulates of quantum mechanics, angular momentum, time-dependent and time-dependent perturbation theory, scattering theory, identical particles, and relativistic electron theory.

  11. Quantum mechanics

    CERN Document Server

    Ghosh, P K

    2014-01-01

    Quantum mechanics, designed for advanced undergraduate and graduate students of physics, mathematics and chemistry, provides a concise yet self-contained introduction to the formal framework of quantum mechanics, its application to physical problems and the interpretation of the theory. Starting with a review of some of the necessary mathematics, the basic concepts are carefully developed in the text. After building a general formalism, detailed treatment of the standard material - the harmonic oscillator, the hydrogen atom, angular momentum theory, symmetry transformations, approximation methods, identical particle and many-particle systems, and scattering theory - is presented. The concluding chapter discusses the interpretation of quantum mechanics. Some of the important topics discussed in the book are the rigged Hilbert space, deformation quantization, path integrals, coherent states, geometric phases, decoherene, etc. This book is characterized by clarity and coherence of presentation.

  12. Quantum mechanics symmetries

    CERN Document Server

    Greiner, Walter

    1989-01-01

    "Quantum Dynamics" is a major survey of quantum theory based on Walter Greiner's long-running and highly successful courses at the University of Frankfurt. The key to understanding in quantum theory is to reinforce lecture attendance and textual study by working through plenty of representative and detailed examples. Firm belief in this principle led Greiner to develop his unique course and to transform it into a remarkable and comprehensive text. The text features a large number of examples and exercises involving many of the most advanced topics in quantum theory. These examples give practical and precise demonstrations of how to use the often subtle mathematics behind quantum theory. The text is divided into five volumes: Quantum Mechanics I - An Introduction, Quantum Mechanics II - Symmetries, Relativistic Quantum Mechanics, Quantum Electrodynamics, Gauge Theory of Weak Interactions. These five volumes take the reader from the fundamental postulates of quantum mechanics up to the latest research in partic...

  13. Quantumness beyond quantum mechanics

    International Nuclear Information System (INIS)

    Sanz, Ángel S

    2012-01-01

    Bohmian mechanics allows us to understand quantum systems in the light of other quantum traits than the well-known ones (coherence, diffraction, interference, tunnelling, discreteness, entanglement, etc.). Here the discussion focusses precisely on two of these interesting aspects, which arise when quantum mechanics is thought within this theoretical framework: the non-crossing property, which allows for distinguishability without erasing interference patterns, and the possibility to define quantum probability tubes, along which the probability remains constant all the way. Furthermore, taking into account this hydrodynamic-like description as a link, it is also shown how this knowledge (concepts and ideas) can be straightforwardly transferred to other fields of physics (for example, the transmission of light along waveguides).

  14. Quantum mechanics

    CERN Document Server

    Rae, Alastair I M

    2007-01-01

    PREFACESINTRODUCTION The Photoelectric Effect The Compton Effect Line Spectra and Atomic Structure De Broglie Waves Wave-Particle Duality The Rest of This Book THE ONE-DIMENSIONAL SCHRÖDINGER EQUATIONS The Time-Dependent Schrödinger Equation The Time-Independent Schrödinger Equation Boundary ConditionsThe Infinite Square Well The Finite Square Well Quantum Mechanical Tunneling The Harmonic Oscillator THE THREE-DIMENSIONAL SCHRÖDINGER EQUATIONS The Wave Equations Separation in Cartesian Coordinates Separation in Spherical Polar Coordinates The Hydrogenic Atom THE BASIC POSTULATES OF QUANTUM MEC

  15. Quantum mechanical simulation methods for studying biological systems

    International Nuclear Information System (INIS)

    Bicout, D.; Field, M.

    1996-01-01

    Most known biological mechanisms can be explained using fundamental laws of physics and chemistry and a full understanding of biological processes requires a multidisciplinary approach in which all the tools of biology, chemistry and physics are employed. An area of research becoming increasingly important is the theoretical study of biological macromolecules where numerical experimentation plays a double role of establishing a link between theoretical models and predictions and allowing a quantitative comparison between experiments and models. This workshop brought researchers working on different aspects of the development and application of quantum mechanical simulation together, assessed the state-of-the-art in the field and highlighted directions for future research. Fourteen lectures (theoretical courses and specialized seminars) deal with following themes: 1) quantum mechanical calculations of large systems, 2) ab initio molecular dynamics where the calculation of the wavefunction and hence the energy and forces on the atoms for a system at a single nuclear configuration are combined with classical molecular dynamics algorithms in order to perform simulations which use a quantum mechanical potential energy surface, 3) quantum dynamical simulations, electron and proton transfer processes in proteins and in solutions and finally, 4) free seminars that helped to enlarge the scope of the workshop. (N.T.)

  16. Quantum mechanics

    CERN Document Server

    Mandl, Franz

    1992-01-01

    The Manchester Physics Series General Editors: D. J. Sandiford; F. Mandl; A. C. Phillips Department of Physics and Astronomy, University of Manchester Properties of Matter B. H. Flowers and E. Mendoza Optics Second Edition F. G. Smith and J. H. Thomson Statistical Physics Second Edition F. Mandl Electromagnetism Second Edition I. S. Grant and W. R. Phillips Statistics R. J. Barlow Solid State Physics Second Edition J. R. Hook and H. E. Hall Quantum Mechanics F. Mandl Particle Physics Second Edition B. R. Martin and G. Shaw The Physics of Stars Second Edition A. C. Phillips Computing for Scient

  17. Some studies on arithmetical chaos in classical and quantum mechanics

    International Nuclear Information System (INIS)

    Bolte, J.

    1993-04-01

    Several aspects of classical and quantum mechanics applied to a class of strongly chaotic systems are studied. The latter consists of single particles moving without external forces on surfaces of constant negative Gaussian curvature whose corresponding fundamental groups are supplied with an arithmetic structure. It is shown that the arithmetical features of the considered systems lead to exceptional properties of the corresponding spectra of lengths of closed geodesics (periodic orbits). The most significant one is an exponential growth of degeneracies in these geodesic length spectra. Furthermore, the arithmetical systems are distinguished by a structure that appears as a generalization of geometric symmetries. These pseudosymmetries occur in the quantization of the classical arithmetic systems as Hecke operators, which form an infinite algebra of self-adjoint operators commuting with the Hamiltonian. The statistical properties of quantum energies in the arithmetical systems have previously been identified as exceptional. They do not fit into the general scheme of random matrix theory. It is shown with the help of a simplified model for the spectral form factor how the spectral statistics in arithmetical quantum chaos can be understood by the properties of the corresponding classical geodesic length spectra. A decisive role is played by the exponentially increasing multiplicities of lengths. The model developed for the level spacings distribution and for the number variance is compared to the corresponding quantities obtained from quantum energies for a specific arithmetical system. Finally, the convergence properties of a representation for the Selberg zeta function as a Dirichlet series are studied. It turns out that the exceptional classical and quantum mechanical properties shared by the arithmetical systems prohibit a convergence of this important function in the physically interesting domain. (orig.)

  18. Quantum mechanics

    International Nuclear Information System (INIS)

    Ghatak, A.K.; Lokanathan, S.

    1975-01-01

    This textbook on quantum mechanics is intended for students at the graduate and post-graduate level. A balanced account of theory and applications is presented. Emphasis is laid on making results plausible and methods to be followed in solving problems. The various chapters in the book are devoted to the following: (1) Wave particle duality and uncertainty principle (2) Wave packets and time-dependent Schroedinger equation (3) Simple solutions of Schroedinger equation (4) Vector spaces and linear operators : Dirac notation (5) Angular momentum and spin (6) Addition of angular momenta (7) Time independent perturbation theory (8) The variational method (9) The WKB approximation (10) Elementary theory of scattering (11) Time-dependent perturbation theory (12) Motion in a magnetic field (13) Interaction of radiation with matter and (14) Relativistic theory. (A.K.)

  19. Physics: quantum mechanics

    International Nuclear Information System (INIS)

    Basdevant, J.L.

    1983-01-01

    This book is the second part of the physic lectures on quantum mechanics from Ecole Polytechnique. It contains some physic complements a little more thoroughly studied, mathematical complements to which refer, and an exercise and problem collection [fr

  20. Quantum Mechanics/Molecular Mechanics Study of the Sialyltransferase Reaction Mechanism.

    Science.gov (United States)

    Hamada, Yojiro; Kanematsu, Yusuke; Tachikawa, Masanori

    2016-10-11

    The sialyltransferase is an enzyme that transfers the sialic acid moiety from cytidine 5'-monophospho-N-acetyl-neuraminic acid (CMP-NeuAc) to the terminal position of glycans. To elucidate the catalytic mechanism of sialyltransferase, we explored the potential energy surface along the sialic acid transfer reaction coordinates by the hybrid quantum mechanics/molecular mechanics method on the basis of the crystal structure of sialyltransferase CstII. Our calculation demonstrated that CstII employed an S N 1-like reaction mechanism via the formation of a short-lived oxocarbenium ion intermediate. The computational barrier height was 19.5 kcal/mol, which reasonably corresponded with the experimental reaction rate. We also found that two tyrosine residues (Tyr156 and Tyr162) played a vital role in stabilizing the intermediate and the transition states by quantum mechanical interaction with CMP.

  1. Quantum mechanics with quantum time

    International Nuclear Information System (INIS)

    Kapuscik, E.

    1984-01-01

    Using a non-canonical Lie structure of classical mechanics a new algebra of quantum mechanical observables is constructed. The new algebra, in addition to the notion of classical time, makes it possible to introduce the notion of quantum time. A new type of uncertainty relation is derived. (author)

  2. Quantum mechanics concept assessment: Development and validation study

    Directory of Open Access Journals (Sweden)

    Homeyra R. Sadaghiani

    2015-03-01

    Full Text Available As part of an ongoing investigation of students’ learning in first semester upper-division quantum mechanics, we needed a high-quality conceptual assessment instrument for comparing outcomes of different curricular approaches. The process of developing such a tool started with converting a preliminary version of a 14-item open-ended quantum mechanics assessment tool (QMAT to a multiple-choice (MC format. Further question refinement, development of effective distractors, adding new questions, and robust statistical analysis has led to a 31-item quantum mechanics concept assessment (QMCA test. The QMCA is used as post-test only to assess students’ knowledge about five main topics of quantum measurement: the time-independent Schrödinger equation, wave functions and boundary conditions, time evolution, and probability density. During two years of testing and refinement, the QMCA has been given in alpha (N=61 and beta versions (N=263 to students in upper division quantum mechanics courses at 11 different institutions with an average post-test score of 54%. By allowing for comparisons of student learning across different populations and institutions, the QMCA provides instructors and researchers a more standard measure of effectiveness of different curricula or teaching strategies on student conceptual understanding of quantum mechanics. In this paper, we discuss the construction of effective distractors and the use of student interviews and expert feedback to revise and validate both questions and distractors. We include the results of common statistical tests of reliability and validity, which suggest the instrument is presently in a stable, usable, and promising form.

  3. Study of quantum spin correlations of relativistic electron pairs - Testing nonlocality of relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Bodek, K.; Rozpędzik, D.; Zejma, J.; Caban, P.; Rembieliński, J.; Włodarczyk, M.; Ciborowski, J.; Enders, J.; Köhler, A.; Kozela, A.

    2013-01-01

    The Polish-German project QUEST aims at studying relativistic quantum spin correlations of the Einstein-Rosen-Podolsky-Bohm type, through measurement of the correlation function and the corresponding probabilities for relativistic electron pairs. The results will be compared to theoretical predictions obtained by us within the framework of relativistic quantum mechanics, based on assumptions regarding the form of the relativistic spin operator. Agreement or divergence will be interpreted in the context of non-uniqueness of the relativistic spin operator in quantum mechanics as well as dependence of the correlation function on the choice of observables representing the spin. Pairs of correlated electrons will originate from the Mo/ller scattering of polarized 15 MeV electrons provided by the superconducting Darmstadt electron linear accelerator S-DALINAC, TU Darmstadt, incident on a Be target. Spin projections will be determined using the Mott polarimetry technique. Measurements (starting 2013) are planned for longitudinal and transverse beam polarizations and different orientations of the beam polarization vector w.r.t. the Mo/ller scattering plane. This is the first project to study relativistic spin correlations for particles with mass

  4. Quantum Mechanics Concept Assessment: Development and Validation Study

    Science.gov (United States)

    Sadaghiani, Homeyra R.; Pollock, Steven J.

    2015-01-01

    As part of an ongoing investigation of students' learning in first semester upper-division quantum mechanics, we needed a high-quality conceptual assessment instrument for comparing outcomes of different curricular approaches. The process of developing such a tool started with converting a preliminary version of a 14-item open-ended quantum…

  5. Probability in quantum mechanics

    Directory of Open Access Journals (Sweden)

    J. G. Gilson

    1982-01-01

    Full Text Available By using a fluid theory which is an alternative to quantum theory but from which the latter can be deduced exactly, the long-standing problem of how quantum mechanics is related to stochastic processes is studied. It can be seen how the Schrödinger probability density has a relationship to time spent on small sections of an orbit, just as the probability density has in some classical contexts.

  6. Fundamentals of Quantum Mechanics

    Science.gov (United States)

    Tang, C. L.

    2005-06-01

    Quantum mechanics has evolved from a subject of study in pure physics to one with a wide range of applications in many diverse fields. The basic concepts of quantum mechanics are explained in this book in a concise and easy-to-read manner emphasising applications in solid state electronics and modern optics. Following a logical sequence, the book is focused on the key ideas and is conceptually and mathematically self-contained. The fundamental principles of quantum mechanics are illustrated by showing their application to systems such as the hydrogen atom, multi-electron ions and atoms, the formation of simple organic molecules and crystalline solids of practical importance. It leads on from these basic concepts to discuss some of the most important applications in modern semiconductor electronics and optics. Containing many homework problems and worked examples, the book is suitable for senior-level undergraduate and graduate level students in electrical engineering, materials science and applied physics. Clear exposition of quantum mechanics written in a concise and accessible style Precise physical interpretation of the mathematical foundations of quantum mechanics Illustrates the important concepts and results by reference to real-world examples in electronics and optoelectronics Contains homeworks and worked examples, with solutions available for instructors

  7. 2D Quantum Mechanical Study of Nanoscale MOSFETs

    Science.gov (United States)

    Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, B.; Kwak, Dochan (Technical Monitor)

    2000-01-01

    With the onset of quantum confinement in the inversion layer in nanoscale MOSFETs, behavior of the resonant level inevitably determines all device characteristics. While most classical device simulators take quantization into account in some simplified manner, the important details of electrostatics are missing. Our work addresses this shortcoming and provides: (a) a framework to quantitatively explore device physics issues such as the source-drain and gate leakage currents, DIBL, and threshold voltage shift due to quantization, and b) a means of benchmarking quantum corrections to semiclassical models (such as density-gradient and quantum-corrected MEDICI). We have developed physical approximations and computer code capable of realistically simulating 2-D nanoscale transistors, using the non-equilibrium Green's function (NEGF) method. This is the most accurate full quantum model yet applied to 2-D device simulation. Open boundary conditions and oxide tunneling are treated on an equal footing. Electrons in the ellipsoids of the conduction band are treated within the anisotropic effective mass approximation. We present the results of our simulations of MIT 25, 50 and 90 nm "well-tempered" MOSFETs and compare them to those of classical and quantum corrected models. The important feature of quantum model is smaller slope of Id-Vg curve and consequently higher threshold voltage. Surprisingly, the self-consistent potential profile shows lower injection barrier in the channel in quantum case. These results are qualitatively consistent with ID Schroedinger-Poisson calculations. The effect of gate length on gate-oxide leakage and subthreshold current has been studied. The shorter gate length device has an order of magnitude smaller current at zero gate bias than the longer gate length device without a significant trade-off in on-current. This should be a device design consideration.

  8. Quantum mechanics. An introduction

    International Nuclear Information System (INIS)

    Lesch, H.

    2008-01-01

    The following topics are dealt with: The way to quantum mechanics starting from thermal radiation and the stability of matter, Heisenberg's uncertainty relation, the impact of quantum mechanics on technology, the description of the big bang by means of quantum mechanics

  9. Quantum mechanics theory and experiment

    CERN Document Server

    Beck, Mark

    2012-01-01

    This textbook presents quantum mechanics at the junior/senior undergraduate level. It is unique in that it describes not only quantum theory, but also presents five laboratories that explore truly modern aspects of quantum mechanics. These laboratories include "proving" that light contains photons, single-photon interference, and tests of local realism. The text begins by presenting the classical theory of polarization, moving on to describe the quantum theory of polarization. Analogies between the two theories minimize conceptual difficulties that students typically have when first presented with quantum mechanics. Furthermore, because the laboratories involve studying photons, using photon polarization as a prototypical quantum system allows the laboratory work to be closely integrated with the coursework. Polarization represents a two-dimensional quantum system, so the introduction to quantum mechanics uses two-dimensional state vectors and operators. This allows students to become comfortable with the mat...

  10. An approximate approach to quantum mechanical study of biomacromolecules

    Science.gov (United States)

    Chen, Xihua

    This thesis summarizes the author's major work in Prof. John Z.H. Zhang's Threoretical Chemistry research group. In Chapter 1, we present a general description of MFCC (molecular fractionation with conjugated caps) method that has been developed in this group to treat biomacromolecules in a divide-and-conquer fashion. Then we give in detail a computational study of MFCC application to peptide/protein that contains disulfide bonds. Continued on the basis of previous MFCC tests, this study provides another numerical support for the accuracy of the MFCC approach to full quantum mechanical calculation of protein/peptide-small molecule interaction. In Chapter 2, we further develop the MFCC scheme for quantum mechanical computation of DNA-ligand interaction energy. We study three oligonuclear acid interaction systems: dinucleotide dCG/water, trinucleotide dCGT/water and a Watson-Crick paired DNA segment dCGT/dGCA. The MFCC interaction energies are found to be in excellent agreement with the corresponding results obtained from the full system ab initio calculations. This study is an exemplification of the application of the general MFCC approach to biomacromolecules. In Chapter 3, firstly, a MFCC-downhill simplex method is proposed to study binding structures of ligands (atoms, ions, or small molecules) in large molecular complex systems. This method employs the MFCC approach to compute the interaction energy-structure relation of the system and implements the downhill simplex algorithm for structural optimization. Secondly, this method is numerically tested on a system of [KCp(18-crown-6)], as a simplest monatomic case study, to optimize the binding position of the potassium cation in a fixed coordination Cp and 18-crown-6 coordinating sphere. The result of the MFCC-downhill simplex optimization shows good agreement with both the crystal structure and with the full-system downhill simplex optimized structure. The effects of the initial structure of the simplex and of the

  11. Testing Nonassociative Quantum Mechanics.

    Science.gov (United States)

    Bojowald, Martin; Brahma, Suddhasattwa; Büyükçam, Umut

    2015-11-27

    The familiar concepts of state vectors and operators in quantum mechanics rely on associative products of observables. However, these notions do not apply to some exotic systems such as magnetic monopoles, which have long been known to lead to nonassociative algebras. Their quantum physics has remained obscure. This Letter presents the first derivation of potentially testable physical results in nonassociative quantum mechanics, based on effective potentials. They imply new effects which cannot be mimicked in usual quantum mechanics with standard magnetic fields.

  12. Engineering quantum mechanics

    CERN Document Server

    Ahn, Doyeol

    2011-01-01

    A clear introduction to quantum mechanics concepts Quantum mechanics has become an essential tool for modern engineering, particularly due to the recent developments in quantum computing as well as the rapid progress in optoelectronic devices. Engineering Quantum Mechanics explains the fundamentals of this exciting field, providing broad coverage of both traditional areas such as semiconductor and laser physics as well as relatively new yet fast-growing areas such as quantum computation and quantum information technology. The book begins with basic quantum mechanics, reviewing measurements and probability, Dirac formulation, the uncertainty principle, harmonic oscillator, angular momentum eigenstates, and perturbation theory. Then, quantum statistical mechanics is explored, from second quantization and density operators to coherent and squeezed states, coherent interactions between atoms and fields, and the Jaynes-Cummings model. From there, the book moves into elementary and modern applications, discussing s...

  13. Lectures on quantum mechanics

    International Nuclear Information System (INIS)

    Weinberg, Steven

    2015-01-01

    Quantum mechanics represents the central revolution of modern natural science and reaches in its importance farely beyond physics. Neither chemistry nor biology on the molecular scale would be understandable without it. Modern information technology from the laptop over the mobile telephone and the flat screen until the supercomputer would be unthinkable without quantum-mechanical effects. It desribes the world on the atomic and subatomic scale and is by this the starting point of our modern worldview. The Nobel-prize carrier Steven Weinberg has done ever among others by his theory of the unification of the weak and the electromagnetic interaction one of the most important contributions to this revolution. In this book he reproduces his personal view of quantum mechanics, which captivates by its strictly logic construction, precise linguistic representation, and mathematical clearness and completeness. This book appeals to studyings of natural sciences, especially of physics. Accompanied is the test by exercise problems, which allow the studying to apply immediately the knowledge, but also test their understanding. Because of its precision and clearness ''Lectures on Quantum Mechanics'' by Weinberg is also essentially suited for the self-study.

  14. Extended quantum mechanics

    International Nuclear Information System (INIS)

    Pavel Bona

    2000-01-01

    The work can be considered as an essay on mathematical and conceptual structure of nonrelativistic quantum mechanics which is related here to some other (more general, but also to more special and 'approximative') theories. Quantum mechanics is here primarily reformulated in an equivalent form of a Poisson system on the phase space consisting of density matrices, where the 'observables', as well as 'symmetry generators' are represented by a specific type of real valued (densely defined) functions, namely the usual quantum expectations of corresponding selfjoint operators. It is shown in this paper that inclusion of additional ('nonlinear') symmetry generators (i. e. 'Hamiltonians') into this reformulation of (linear) quantum mechanics leads to a considerable extension of the theory: two kinds of quantum 'mixed states' should be distinguished, and operator - valued functions of density matrices should be used in the role of 'nonlinear observables'. A general framework for physical theories is obtained in this way: By different choices of the sets of 'nonlinear observables' we obtain, as special cases, e.g. classical mechanics on homogeneous spaces of kinematical symmetry groups, standard (linear) quantum mechanics, or nonlinear extensions of quantum mechanics; also various 'quasiclassical approximations' to quantum mechanics are all sub theories of the presented extension of quantum mechanics - a version of the extended quantum mechanics. A general interpretation scheme of extended quantum mechanics extending the usual statistical interpretation of quantum mechanics is also proposed. Eventually, extended quantum mechanics is shown to be (included into) a C * -algebraic (hence linear) quantum theory. Mathematical formulation of these theories is presented. The presentation includes an analysis of problems connected with differentiation on infinite-dimensional manifolds, as well as a solution of some problems connected with the work with only densely defined unbounded

  15. A study of deterministic models for quantum mechanics

    International Nuclear Information System (INIS)

    Sutherland, R.

    1980-01-01

    A theoretical investigation is made into the difficulties encountered in constructing a deterministic model for quantum mechanics and into the restrictions that can be placed on the form of such a model. The various implications of the known impossibility proofs are examined. A possible explanation for the non-locality required by Bell's proof is suggested in terms of backward-in-time causality. The efficacy of the Kochen and Specker proof is brought into doubt by showing that there is a possible way of avoiding its implications in the only known physically realizable situation to which it applies. A new thought experiment is put forward to show that a particle's predetermined momentum and energy values cannot satisfy the laws of momentum and energy conservation without conflicting with the predictions of quantum mechanics. Attention is paid to a class of deterministic models for which the individual outcomes of measurements are not dependent on hidden variables associated with the measuring apparatus and for which the hidden variables of a particle do not need to be randomized after each measurement

  16. Theoretical physics. Quantum mechanics

    International Nuclear Information System (INIS)

    Rebhan, Eckhard

    2008-01-01

    From the first in two comprehensive volumes appeared Theoretical Physics of the author by this after Mechanics and Electrodynamics also Quantum mechanics appears as thinner single volume. First the illustrative approach via wave mechanics is reproduced. The more abstract Hilbert-space formulation introduces the author later by postulates, which are because of the preceding wave mechanics sufficiently plausible. All concepts of quantum mechanics, which contradict often to the intuitive understanding formed by macroscopic experiences, are extensively discussed and made by means of many examples as well as problems - in the largest part provided with solutions - understandable. To the interpretation of quantum mechanics an extensive special chapter is dedicated. this book arose from courses on theoretical physics, which the author has held at the Heinrich-Heine University in Duesseldorf, and was in numerous repetitions fitted to the requirement of the studyings. it is so designed that it is also after the study suited as reference book or for the renewing. All problems are very thoroughly and such extensively studied that each step is separately reproducible. About motivation and good understandability is cared much

  17. Advanced Visual Quantum Mechanics

    CERN Document Server

    Thaller, Bernd

    2005-01-01

    Advanced Visual Quantum Mechanics is a systematic effort to investigate and to teach quantum mechanics with the aid of computer-generated animations. It is a self-contained textbook that combines selected topics from atomic physics (spherical symmetry, the hydrogen atom, and particles with spin) with an introduction to quantum information theory (qubits, EPR paradox, teleportation, quantum computers). It explores relativistic quantum mechanics and the strange behavior of Dirac equation solutions. A series of appendices covers important topics from perturbation and scattering theory. The book places an emphasis on ideas and concepts, with a fair to moderate amount of mathematical rigor. Though this book stands alone, it can also be paired with Thaller Visual Quantum Mechanics to form a comprehensive course in quantum mechanics. The software for the first book earned the European Academic Software Award 2000 for outstanding innovation in its field.

  18. Quantum mechanics in chemistry

    CERN Document Server

    Schatz, George C

    2002-01-01

    Intended for graduate and advanced undergraduate students, this text explores quantum mechanical techniques from the viewpoint of chemistry and materials science. Dynamics, symmetry, and formalism are emphasized. An initial review of basic concepts from introductory quantum mechanics is followed by chapters examining symmetry, rotations, and angular momentum addition. Chapter 4 introduces the basic formalism of time-dependent quantum mechanics, emphasizing time-dependent perturbation theory and Fermi's golden rule. Chapter 5 sees this formalism applied to the interaction of radiation and matt

  19. Dynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region

    International Nuclear Information System (INIS)

    Moin, Syed Tarique; Hofer, Thomas S.; Weiss, Alexander K. H.; Rode, Bernd M.

    2013-01-01

    Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment

  20. Dynamics of ligand exchange mechanism at Cu(II) in water: an ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region.

    Science.gov (United States)

    Moin, Syed Tarique; Hofer, Thomas S; Weiss, Alexander K H; Rode, Bernd M

    2013-07-07

    Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment.

  1. Quantum mechanics and computation

    International Nuclear Information System (INIS)

    Cirac Sasturain, J. I.

    2000-01-01

    We review how some of the basic principles of Quantum Mechanics can be used in the field of computation. In particular, we explain why a quantum computer can perform certain tasks in a much more efficient way than the computers we have available nowadays. We give the requirements for a quantum system to be able to implement a quantum computer and illustrate these requirements in some particular physical situations. (Author) 16 refs

  2. Quantum mechanics for pedestrians

    CERN Document Server

    Pade, Jochen

    2014-01-01

    This book provides an introduction into the fundamentals of non-relativistic quantum mechanics. In Part 1, the essential principles are developed. Applications and extensions of the formalism can be found in Part 2. The book includes not only material that is presented in traditional textbooks on quantum mechanics, but also discusses in detail current issues such as interaction-free quantum measurements, neutrino oscillations, various topics in the field of quantum information as well as fundamental problems and epistemological questions, such as the measurement problem, entanglement, Bell's inequality, decoherence, and the realism debate. A chapter on current interpretations of quantum mechanics concludes the book. To develop quickly and clearly the main principles of quantum mechanics and its mathematical formulation, there is a systematic change between wave mechanics and algebraic representation in the first chapters. The required mathematical tools are introduced step by step. Moreover, the appendix coll...

  3. Studies on quantum field theory and statistical mechanics

    International Nuclear Information System (INIS)

    Zhang, S.

    1987-01-01

    This dissertation is a summary of research in various areas of theoretical physics and is divided into three parts. In the first part, quantum fluctuations of the recently proposed superconducting cosmic strings are studied. It is found that vortices on the string world sheet represent an important class of fluctuation modes which tend to disorder the system. Both heuristic arguments and detailed renormalization group analysis reveal that these vortices do not appear in bound pairs but rather from a gas of free vortices. Based on this observation we argue that this fluctuation mode violates the topological conservation law on which superconductivity is based. Anomalies and topological aspects of supersymmetric quantum field theories are studied in the second part of this dissertation. Using the superspace formulation of the N = 1 spinning string, we obtain a path integral measure which is free from the world-sheet general coordinate as well as the supersymmetry anomalies and therefore determine the conformal anomaly and critical dimension of the spinning string. We also apply Fujikawa's formalism to computer the chiral anomaly in conformal as well as ordinary supergravity. Finally, we given a Noether-method construction of the supersymmetrized Chern-Simons term in five dimensional supergravity. In the last part of this dissertation, the soliton excitations in the quarter-filled Peierls-Hubbard model are investigated in both the large and the small U limit. For a strictly one dimensional system at zero temperature, we find that solitons in both limits are in one-to-one correspondence, while in the presence of weak three dimensional couplings or at finite temperature, the large U systems differ qualitatively from the small U systems in that the spin associated with the solitons ceases to be a sharp quantum observable

  4. Classicality in quantum mechanics

    International Nuclear Information System (INIS)

    Dreyer, Olaf

    2007-01-01

    In this article we propose a solution to the measurement problem in quantum mechanics. We point out that the measurement problem can be traced to an a priori notion of classicality in the formulation of quantum mechanics. If this notion of classicality is dropped and instead classicality is defined in purely quantum mechanical terms the measurement problem can be avoided. We give such a definition of classicality. It identifies classicality as a property of large quantum system. We show how the probabilistic nature of quantum mechanics is a result of this notion of classicality. We also comment on what the implications of this view are for the search of a quantum theory of gravity

  5. Classicality in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Dreyer, Olaf [Theoretical Physics, Blackett Laboratory, Imperial College London, London, SW7 2AZ (United Kingdom)

    2007-05-15

    In this article we propose a solution to the measurement problem in quantum mechanics. We point out that the measurement problem can be traced to an a priori notion of classicality in the formulation of quantum mechanics. If this notion of classicality is dropped and instead classicality is defined in purely quantum mechanical terms the measurement problem can be avoided. We give such a definition of classicality. It identifies classicality as a property of large quantum system. We show how the probabilistic nature of quantum mechanics is a result of this notion of classicality. We also comment on what the implications of this view are for the search of a quantum theory of gravity.

  6. Introduction to quantum mechanics

    CERN Document Server

    Phillips, A C

    2003-01-01

    Introduction to Quantum Mechanics is an introduction to the power and elegance of quantum mechanics. Assuming little in the way of prior knowledge, quantum concepts are carefully and precisely presented, and explored through numerous applications and problems. Some of the more challenging aspects that are essential for a modern appreciation of the subject have been included, but are introduced and developed in the simplest way possible.Undergraduates taking a first course on quantum mechanics will find this text an invaluable introduction to the field and help prepare them for more adv

  7. Lectures on Quantum Mechanics

    CERN Document Server

    Dirac, Paul Adrien Maurice

    1964-01-01

    The author of this concise, brilliant series of lectures on mathematical methods in quantum mechanics was one of the shining intellects in the field, winning a Nobel prize in 1933 for his pioneering work in the quantum mechanics of the atom. Beyond that, he developed the transformation theory of quantum mechanics (which made it possible to calculate the statistical distribution of certain variables), was one of the major authors of the quantum theory of radiation, codiscovered the Fermi-Dirac statistics, and predicted the existence of the positron.The four lectures in this book were delivered

  8. Fractional quantum mechanics

    CERN Document Server

    Laskin, Nick

    2018-01-01

    Fractional quantum mechanics is a recently emerged and rapidly developing field of quantum physics. This is the first monograph on fundamentals and physical applications of fractional quantum mechanics, written by its founder. The fractional Schrödinger equation and the fractional path integral are new fundamental physical concepts introduced and elaborated in the book. The fractional Schrödinger equation is a manifestation of fractional quantum mechanics. The fractional path integral is a new mathematical tool based on integration over Lévy flights. The fractional path integral method enhances the well-known Feynman path integral framework. Related topics covered in the text include time fractional quantum mechanics, fractional statistical mechanics, fractional classical mechanics and the α-stable Lévy random process. The book is well-suited for theorists, pure and applied mathematicians, solid-state physicists, chemists, and others working with the Schrödinger equation, the path integral technique...

  9. Locality and quantum mechanics.

    Science.gov (United States)

    Unruh, W G

    2018-07-13

    It is argued that it is best not to think of quantum mechanics as non-local, but rather that it is non-realistic.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).

  10. Maximally causal quantum mechanics

    International Nuclear Information System (INIS)

    Roy, S.M.

    1998-01-01

    We present a new causal quantum mechanics in one and two dimensions developed recently at TIFR by this author and V. Singh. In this theory both position and momentum for a system point have Hamiltonian evolution in such a way that the ensemble of system points leads to position and momentum probability densities agreeing exactly with ordinary quantum mechanics. (author)

  11. Questioning quantum mechanics

    Science.gov (United States)

    Frappier, Mélanie

    2018-03-01

    A century after its inception, quantum mechanics continues to puzzle us with dead-and-alive cats, waves "collapsing" into particles, and "spooky action at a distance." In his first book, What Is Real?, science writer and astrophysicist Adam Becker sets out to explore why the physics community is still arguing today about quantum mechanics's true meaning.

  12. Problems in quantum mechanics

    CERN Document Server

    Goldman, Iosif Ilich; Geilikman, B T

    2006-01-01

    This challenging book contains a comprehensive collection of problems in nonrelativistic quantum mechanics of varying degrees of difficulty. It features answers and completely worked-out solutions to each problem. Geared toward advanced undergraduates and graduate students, it provides an ideal adjunct to any textbook in quantum mechanics.

  13. A quantum mechanics/molecular mechanics study on the hydrolysis mechanism of New Delhi metallo-β-lactamase-1.

    Science.gov (United States)

    Zhu, Kongkai; Lu, Junyan; Liang, Zhongjie; Kong, Xiangqian; Ye, Fei; Jin, Lu; Geng, Heji; Chen, Yong; Zheng, Mingyue; Jiang, Hualiang; Li, Jun-Qian; Luo, Cheng

    2013-03-01

    New Delhi metallo-β-lactamase-1 (NDM-1) has emerged as a major global threat to human health for its rapid rate of dissemination and ability to make pathogenic microbes resistant to almost all known β-lactam antibiotics. In addition, effective NDM-1 inhibitors have not been identified to date. In spite of the plethora of structural and kinetic data available, the accurate molecular characteristics of and details on the enzymatic reaction of NDM-1 hydrolyzing β-lactam antibiotics remain incompletely understood. In this study, a combined computational approach including molecular docking, molecular dynamics simulations and quantum mechanics/molecular mechanics calculations was performed to characterize the catalytic mechanism of meropenem catalyzed by NDM-1. The quantum mechanics/molecular mechanics results indicate that the ionized D124 is beneficial to the cleavage of the C-N bond within the β-lactam ring. Meanwhile, it is energetically favorable to form an intermediate if no water molecule coordinates to Zn2. Moreover, according to the molecular dynamics results, the conserved residue K211 plays a pivotal role in substrate binding and catalysis, which is quite consistent with previous mutagenesis data. Our study provides detailed insights into the catalytic mechanism of NDM-1 hydrolyzing meropenem β-lactam antibiotics and offers clues for the discovery of new antibiotics against NDM-1 positive strains in clinical studies.

  14. Quantum chemical study of the mechanism of action of vitamin K epoxide reductase (VKOR)

    Science.gov (United States)

    Deerfield, David, II; Davis, Charles H.; Wymore, Troy; Stafford, Darrel W.; Pedersen, Lee G.

    Possible model, but simplistic, mechanisms for the action of vitamin K epoxide reductase (VKOR) are investigated with quantum mechanical methods (B3LYP/6-311G**). The geometries of proposed model intermediates in the mechanisms are energy optimized. Finally, the energetics of the proposed (pseudo-enzymatic) pathways are compared. We find that the several pathways are all energetically feasible. These results will be useful for designing quantum mechanical/molecular mechanical method (QM/MM) studies of the enzymatic pathway once three-dimensional structural data are determined and available for VKOR.

  15. Understand quantum mechanics

    International Nuclear Information System (INIS)

    Omnes, R.

    2000-01-01

    The author presents the interpretation of quantum mechanics in a simple and direct way. This book may be considered as a complement of specialized books whose aim is to present the mathematical developments of quantum mechanics. As early as the beginning of quantum theory, Bohr, Heisenberg and Pauli proposed the basis of what is today called the interpretation of Copenhagen. This interpretation is still valid but 2 important discoveries have led to renew some aspects of the interpretation of Copenhagen. The first one was the discovery of the decoherence phenomenon which is responsible for the absence of quantum interferences in the macroscopic world. The second discovery was the achievement of the complete derivation of classical physics from quantum physics, it means that the classical determinism fits in the framework of quantum probabilism. A short summary ends each chapter. (A.C.)

  16. Postulates of quantum mechanics

    International Nuclear Information System (INIS)

    Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.

    1977-01-01

    Postulates of quantum mechanics and physical interpretation on observables and their measurement are presented. The physical content of Schroedinger equation, the superposition principle and the physical forecastings are also exposed. In complement are also presented: physical study of a particle in a infinite potential well; study of probability current; mean deviations of two conjugate observables; measurements on a part only of a physical system; density operator; evolution operator; Heisenberg and Schoredinger pictures; gauge invariance; propagator of the Schroedinger equation; unsteady levels lifetime; bound states of a particle in a potential well of any shape; non-bound states of a particle in a well or a potential barrier of some shape; quantum properties of a particle in a one-dimensional periodic structure [fr

  17. Supersymmetry in quantum mechanics

    CERN Document Server

    Cooper, Fred; Sukhatme, Uday

    2001-01-01

    This invaluable book provides an elementary description of supersymmetric quantum mechanics which complements the traditional coverage found in the existing quantum mechanics textbooks. It gives physicists a fresh outlook and new ways of handling quantum-mechanical problems, and also leads to improved approximation techniques for dealing with potentials of interest in all branches of physics. The algebraic approach to obtaining eigenstates is elegant and important, and all physicists should become familiar with this. The book has been written in such a way that it can be easily appreciated by

  18. Relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Ollitrault, J.Y.

    1998-12-01

    These notes form an introduction to relativistic quantum mechanics. The mathematical formalism has been reduced to the minimum in order to enable the reader to calculate elementary physical processes. The second quantification and the field theory are the logical followings of this course. The reader is expected to know analytical mechanics (Lagrangian and Hamiltonian), non-relativistic quantum mechanics and some basis of restricted relativity. The purpose of the first 3 chapters is to define the quantum mechanics framework for already known notions about rotation transformations, wave propagation and restricted theory of relativity. The next 3 chapters are devoted to the application of relativistic quantum mechanics to a particle with 0,1/5 and 1 spin value. The last chapter deals with the processes involving several particles, these processes require field theory framework to be thoroughly described. (A.C.)

  19. Mathematics and quantum mechanics

    International Nuclear Information System (INIS)

    Santander, M.

    2000-01-01

    Several episodes in the relation between Mathematics and Quantum Mechanics are discussed; and the emphasis is put in the existence of multiple and sometimes unexpected connections between ideas originating in Mathematics and in Quantum Physics. The question of the unresasonable effectiveness of Mathematics in Physics is also presented in the same light. (Author) 3 refs

  20. Primer of quantum mechanics

    CERN Document Server

    Chester, Marvin

    2003-01-01

    Introductory text examines the classical quantum bead on a track: its state and representations; operator eigenvalues; harmonic oscillator and bound bead in a symmetric force field; and bead in a spherical shell. Also, spin, matrices and structure of quantum mechanics; simplest atom; indistinguishable particles; and stationary-state perturbation theory.

  1. Lectures on Quantum Mechanics

    Science.gov (United States)

    Weinberg, Steven

    2015-09-01

    Preface; Notation; 1. Historical introduction; 2. Particle states in a central potential; 3. General principles of quantum mechanics; 4. Spin; 5. Approximations for energy eigenstates; 6. Approximations for time-dependent problems; 7. Potential scattering; 8. General scattering theory; 9. The canonical formalism; 10. Charged particles in electromagnetic fields; 11. The quantum theory of radiation; 12. Entanglement; Author index; Subject index.

  2. Quantum mechanics of leptogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Mendizabal Cofre, Sebastian

    2010-08-15

    Leptogenesis is an attractive mechanism that simultaneously explains the matterantimatter asymmetry of the universe as well as the small masses of the standard model neutrinos. This is performed by naturally extending the standard model with the insertion of right handed neutrinos. Leptogenesis is usually studied via the semi-classical Boltzmann equations. However, these equations suffer from basic conceptual problems and they lack to include many quantum phenomena, such as memory effects and coherence oscillations. In order to fully describe leptogenesis, a full quantum treatment is required. In this work we show how to address leptogenesis systematically in a purely quantum way. We start by studying scalar and fermionic excitations in a plasma by solving the Kadanoff-Baym equations of motion for Green's functions, with significant emphasis on the initial and boundary conditions of the solutions. We compute analytically the asymmetry generated from the departure of equilibrium of a particle in a thermal bath. The comparison with the semi-classical Boltzmann approach is also analysed, leading to a qualitative difference between both methods. The non-locality of the Kadanoff-Baym equations shows how off-shell effects can have a huge impact on the generated asymmetry, effects that cannot be studied with the Boltzmann equations. The insertion of standard model interactions like the decay widths for the particles of the bath is also discussed. We explain how with a trivial insertion of these widths we regain locality on the processes, i.e. we regain the Boltzmann equations. (orig.)

  3. Quantum mechanics of leptogenesis

    International Nuclear Information System (INIS)

    Mendizabal Cofre, Sebastian

    2009-07-01

    Leptogenesis is an attractive mechanism that simultaneously explains the matterantimatter asymmetry of the universe as well as the small masses of the standard model neutrinos. This is performed by naturally extending the standard model with the insertion of right handed neutrinos. Leptogenesis is usually studied via the semi-classical Boltzmann equations. However, these equations suffer from basic conceptual problems and they lack to include many quantum phenomena, such as memory effects and coherence oscillations. In order to fully describe leptogenesis, a full quantum treatment is required. In this work we show how to address leptogenesis systematically in a purely quantum way. We start by studying scalar and fermionic excitations in a plasma by solving the Kadanoff-Baym equations of motion for Green's functions, with significant emphasis on the initial and boundary conditions of the solutions. We compute analytically the asymmetry generated from the departure of equilibrium of a particle in a thermal bath. The comparison with the semi-classical Boltzmann approach is also analysed, leading to a qualitative difference between both methods. The non-locality of the Kadanoff-Baym equations shows how off-shell effects can have a huge impact on the generated asymmetry, effects that cannot be studied with the Boltzmann equations. The insertion of standard model interactions like the decay widths for the particles of the bath is also discussed. We explain how with a trivial insertion of these widths we regain locality on the processes, i.e. we regain the Boltzmann equations. (orig.)

  4. Beyond conventional quantum mechanics

    International Nuclear Information System (INIS)

    Ghirardi, C.

    1991-10-01

    The author reviews some recent attempts to overcome the conceptual difficulties encountered by trying to interpret quantum mechanics as giving a complete, objective and unified description of natural phenomena. 38 refs

  5. Physics: quantum mechanics

    International Nuclear Information System (INIS)

    Basdevant, J.L.

    1983-01-01

    From important experiment descriptions (sometimes, intentionally simplified), the essential concepts in Quantum Mechanics are first introduced. Wave function notion is described, Schroedinger equation is established, and, after applications rich in physical signification, quantum state and Hilbert space formalism are introduced, which will help to understand many essential phenomena. Then the quantum mechanic general formulation is written and some important consequences are deduced. This formalism is applied to a simple physical problem series (angular momentum, hydrogen atom, etc.) aiming at assimilating the theory operation and its application [fr

  6. Supersymmetric symplectic quantum mechanics

    Science.gov (United States)

    de Menezes, Miralvo B.; Fernandes, M. C. B.; Martins, Maria das Graças R.; Santana, A. E.; Vianna, J. D. M.

    2018-02-01

    Symplectic Quantum Mechanics SQM considers a non-commutative algebra of functions on a phase space Γ and an associated Hilbert space HΓ to construct a unitary representation for the Galilei group. From this unitary representation the Schrödinger equation is rewritten in phase space variables and the Wigner function can be derived without the use of the Liouville-von Neumann equation. In this article we extend the methods of supersymmetric quantum mechanics SUSYQM to SQM. With the purpose of applications in quantum systems, the factorization method of the quantum mechanical formalism is then set within supersymmetric SQM. A hierarchy of simpler hamiltonians is generated leading to new computation tools for solving the eigenvalue problem in SQM. We illustrate the results by computing the states and spectra of the problem of a charged particle in a homogeneous magnetic field as well as the corresponding Wigner function.

  7. Lectures on quantum mechanics

    CERN Document Server

    Weinberg, Steven

    2013-01-01

    Nobel Laureate Steven Weinberg combines his exceptional physical insight with his gift for clear exposition to provide a concise introduction to modern quantum mechanics. Ideally suited to a one-year graduate course, this textbook is also a useful reference for researchers. Readers are introduced to the subject through a review of the history of quantum mechanics and an account of classic solutions of the Schrödinger equation, before quantum mechanics is developed in a modern Hilbert space approach. The textbook covers many topics not often found in other books on the subject, including alternatives to the Copenhagen interpretation, Bloch waves and band structure, the Wigner–Eckart theorem, magic numbers, isospin symmetry, the Dirac theory of constrained canonical systems, general scattering theory, the optical theorem, the 'in-in' formalism, the Berry phase, Landau levels, entanglement and quantum computing. Problems are included at the ends of chapters, with solutions available for instructors at www.cam...

  8. Quantum mechanical suppression of chaos

    International Nuclear Information System (INIS)

    Bluemel, R.; Smilansky, U.

    1990-01-01

    The relation between determinism and predictability is the central issue in the study of 'deterministic chaos'. Much knowledge has been accumulated in the past 10 years about the chaotic dynamics of macroscopic (classical) systems. The implications of chaos in the microscopic quantum world is examined, in other words, how to reconcile the correspondence principle with the inherent uncertainties which reflect the wave nature of quantum dynamics. Recent atomic physics experiments demonstrate clearly that chaos is relevant to the microscopic world. In particular, such experiments emphasise the urgent need to clarify the genuine quantum mechanism which imposes severe limitations on quantum dynamics, and renders it so very different from its classical counterpart. (author)

  9. Effective equations for the quantum pendulum from momentous quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, Hector H.; Chacon-Acosta, Guillermo [Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Departamento de Matematicas Aplicadas y Sistemas, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40, Mexico D. F. 01120 (Mexico)

    2012-08-24

    In this work we study the quantum pendulum within the framework of momentous quantum mechanics. This description replaces the Schroedinger equation for the quantum evolution of the system with an infinite set of classical equations for expectation values of configuration variables, and quantum dispersions. We solve numerically the effective equations up to the second order, and describe its evolution.

  10. Geometric Aspects of Quantum Mechanics and Quantum Entanglement

    International Nuclear Information System (INIS)

    Chruscinski, Dariusz

    2006-01-01

    It is shown that the standard non-relativistic Quantum Mechanics gives rise to elegant and rich geometrical structures. The space of quantum states is endowed with nontrivial Fubini-Study metric which is responsible for the 'peculiarities' of the quantum world. We show that there is also intricate connection between geometrical structures and quantum entanglement

  11. Why quantum mechanics?

    International Nuclear Information System (INIS)

    Landsberg, P.T.

    1988-01-01

    It is suggested that an oversight occurred in classical mechanics when time-derivatives of observables were treated on the same footing as the undifferentiated observables. Removal of this oversight points in the direction of quantum mechanics. Additional light is thrown on uncertainty relations and on quantum mechanics, as a possible form of a subtle statistical mechanics, by the formulation of a classical uncertainty relation for a very simple model. The existence of universal motion, i.e., of zero-point energy, is lastly made plausible in terms of a gravitational constant which is time-dependent. By these three considerations an attempt is made to link classical and quantum mechanics together more firmly, thus giving a better understanding of the latter

  12. Quo Vadis Quantum Mechanics?

    CERN Document Server

    Dolev, S; Kolenda, N

    2005-01-01

    For more than a century, quantum mechanics has served as a very powerful theory that has expanded physics and technology far beyond their classical limits, yet it has also produced some of the most difficult paradoxes known to the human mind. This book represents the combined efforts of sixteen of today's most eminent theoretical physicists to lay out future directions for quantum physics. The authors include Yakir Aharonov, Anton Zeilinger; the Nobel laureates Anthony Leggett and Geradus 't Hooft; Basil Hiley, Lee Smolin and Henry Stapp. Following a foreword by Roger Penrose, the individual chapters address questions such as quantum non-locality, the measurement problem, quantum insights into relativity, cosmology and thermodynamics, and the possible bearing of quantum phenomena on biology and consciousness.

  13. Supersymmetry and quantum mechanics

    International Nuclear Information System (INIS)

    Cooper, F.; Sukhatme, U.

    1995-01-01

    In the past ten years, the ideas of supersymmetry have been profitably applied to many nonrelativistic quantum mechanical problems. In particular, there is now a much deeper understanding of why certain potentials are analytically solvable and an array of powerful new approximation methods for handling potentials which are not exactly solvable. In this report, we review the theoretical formulation of supersymmetric quantum mechanics and discuss many applications. Exactly solvable potentials can be understood in terms of a few basic ideas which include supersymmetric partner potentials, shape invariance and operator transformations. Familiar solvable potentials all have the property of shape invariance. We describe new exactly solvable shape invariant potentials which include the recently discovered self-similar potentials as a special case. The connection between inverse scattering, isospectral potentials and supersymmetric quantum mechanics is discussed and multi-soliton solutions of the KdV equation are constructed. Approximation methods are also discussed within the framework of supersymmetric quantum mechanics and in particular it is shown that a supersymmetry inspired WKB approximation is exact for a class of shape invariant potentials. Supersymmetry ideas give particularly nice results for the tunneling rate in a double well potential and for improving large N expansions. We also discuss the problem of a charged Dirac particle in an external magnetic field and other potentials in terms of supersymmetric quantum mechanics. Finally, we discuss structures more general than supersymmetric quantum mechanics such as parasupersymmetric quantum mechanics in which there is a symmetry between a boson and a para-fermion of order p. ((orig.))

  14. Time in quantum mechanics

    CERN Document Server

    Mayato, R; Egusquiza, I

    2002-01-01

    The treatment of time in quantum mechanics is still an important and challenging open question in the foundation of the theory. This book describes the problems, and the attempts and achievements in defining, formalizing and measuring different time quantities in quantum theory, such as the parametric (clock) time, tunneling times, decay times, dwell times, delay times, arrival times or jump times. This multiauthored book, written as an introductory guide for the non-initiated as well as a useful source of information for the expert, covers many of the open questions. A brief historical overview is to be found in the introduction. It is followed by 12 chapters devoted to conceptual and theoretical investigations as well as experimental issues in quantum-mechanical time measurements. This unique monograph should attract physicists as well as philosophers of science working in the foundations of quantum physics.

  15. Axiomation of quantum mechanics

    International Nuclear Information System (INIS)

    Kotecky, R.

    1975-01-01

    Deeper understanding of the basic structure of the formalism of the modern quantum theory (as has been established during its 50 years' stormy development) has been brought about by its axiomatization - by founding the formalism merely on experimentally directly accountable postulates without referring to historical development, without any a priori nonessential or empirically nonexplicable assumptions. A summary is given of the common formalism of quantum mechanics and its most significant axiomatizations. The assumptions are discussed under which respective axiomatically described abstract structures may be modelled by means of the common formalisn of quantum theory (established on the theory of Hilbert spaces). (author)

  16. Analytical mechanics for relativity and quantum mechanics

    CERN Document Server

    Johns, Oliver Davis

    2011-01-01

    Analytical Mechanics for Relativity and Quantum Mechanics is an innovative and mathematically sound treatment of the foundations of analytical mechanics and the relation of classical mechanics to relativity and quantum theory. It is intended for use at the introductory graduate level. A distinguishing feature of the book is its integration of special relativity into teaching of classical mechanics. After a thorough review of the traditional theory, Part II of the book introduces extended Lagrangian and Hamiltonian methods that treat time as a transformable coordinate rather than the fixed parameter of Newtonian physics. Advanced topics such as covariant Langrangians and Hamiltonians, canonical transformations, and Hamilton-Jacobi methods are simplified by the use of this extended theory. And the definition of canonical transformation no longer excludes the Lorenz transformation of special relativity. This is also a book for those who study analytical mechanics to prepare for a critical exploration of quantum...

  17. Hilbert space and quantum mechanics

    CERN Document Server

    Gallone, Franco

    2015-01-01

    The topics of this book are the mathematical foundations of non-relativistic quantum mechanics and the mathematical theory they require. The main characteristic of the book is that the mathematics is developed assuming familiarity with elementary analysis only. Moreover, all the proofs are carried out in detail. These features make the book easily accessible to readers with only the mathematical training offered by undergraduate education in mathematics or in physics, and also ideal for individual study. The principles of quantum mechanics are discussed with complete mathematical accuracy and an effort is made to always trace them back to the experimental reality that lies at their root. The treatment of quantum mechanics is axiomatic, with definitions followed by propositions proved in a mathematical fashion. No previous knowledge of quantum mechanics is required. This book is designed so that parts of it can be easily used for various courses in mathematics and mathematical physics, as suggested in the Pref...

  18. Time Dependent Quantum Mechanics

    OpenAIRE

    Morrison, Peter G.

    2012-01-01

    We present a systematic method for dealing with time dependent quantum dynamics, based on the quantum brachistochrone and matrix mechanics. We derive the explicit time dependence of the Hamiltonian operator for a number of constrained finite systems from this formalism. Once this has been achieved we go on to calculate the wavevector as a function of time, in order to demonstrate the use of matrix methods with respect to several concrete examples. Interesting results are derived for elliptic ...

  19. Proceedings of quantum field theory, quantum mechanics, and quantum optics

    International Nuclear Information System (INIS)

    Dodonov, V.V.; Man; ko, V.I.

    1991-01-01

    This book contains papers presented at the XVIII International Colloquium on Group Theoretical Methods in Physics held in Moscow on June 4-9, 1990. Topics covered include; applications of algebraic methods in quantum field theory, quantum mechanics, quantum optics, spectrum generating groups, quantum algebras, symmetries of equations, quantum physics, coherent states, group representations and space groups

  20. Manin's quantum spaces and standard quantum mechanics

    International Nuclear Information System (INIS)

    Floratos, E.G.

    1990-01-01

    Manin's non-commutative coordinate algebra of quantum groups is shown to be identical, for unitary coordinates, with the conventional operator algebras of quantum mechanics. The deformation parameter q is a pure phase for unitary coordinates. When q is a root of unity. Manin's algebra becomes the matrix algebra of quantum mechanics for a discretized and finite phase space. Implications for quantum groups and the associated non-commutative differential calculus of Wess and Zumino are discussed. (orig.)

  1. Learning quantum field theory from elementary quantum mechanics

    International Nuclear Information System (INIS)

    Gosdzinsky, P.; Tarrach, R.

    1991-01-01

    The study of the Dirac delta potentials in more than one dimension allows the introduction within the framework of elementary quantum mechanics of many of the basic concepts of modern quantum field theory: regularization, renormalization group, asymptotic freedom, dimensional transmutation, triviality, etc. It is also interesting, by itself, as a nonstandard quantum mechanical problem

  2. From wave mechanics to quantum chemistry

    International Nuclear Information System (INIS)

    Daudel, R.

    1996-01-01

    The origin of wave mechanics, which is now called quantum mechanics, is evoked. The main stages of the birth of quantum chemistry are related as resulting from the application of quantum mechanics to the study of molecular properties and chemical reactions. (author). 14 refs

  3. Relativistic Quantum Mechanics

    International Nuclear Information System (INIS)

    Antoine, J-P

    2004-01-01

    The aim of relativistic quantum mechanics is to describe the finer details of the structure of atoms and molecules, where relativistic effects become nonnegligible. It is a sort of intermediate realm, between the familiar nonrelativistic quantum mechanics and fully relativistic quantum field theory, and thus it lacks the simplicity and elegance of both. Yet it is a necessary tool, mostly for quantum chemists. Pilkuhn's book offers to this audience an up-to-date survey of these methods, which is quite welcome since most previous textbooks are at least ten years old. The point of view of the author is to start immediately in the relativistic domain, following the lead of Maxwell's equations rather than classical mechanics, and thus to treat the nonrelativistic version as an approximation. Thus Chapter 1 takes off from Maxwell's equations (in the noncovariant Coulomb gauge) and gradually derives the basic aspects of Quantum Mechanics in a rather pedestrian way (states and observables, Hilbert space, operators, quantum measurement, scattering,. Chapter 2 starts with the Lorentz transformations, then continues with the Pauli spin equation and the Dirac equation and some of their applications (notably the hydrogen atom). Chapter 3 is entitled 'Quantum fields and particles', but falls short of treating quantum field theory properly: only creation/annihilation operators are considered, for a particle in a box. The emphasis is on two-electron states (the Pauli principle, the Foldy--Wouthuysen elimination of small components of Dirac spinors, Breit projection operators. Chapter 4 is devoted to scattering theory and the description of relativistic bound states. Chapter 5, finally, covers hyperfine interactions and radiative corrections. As we said above, relativistic quantum mechanics is by nature limited in scope and rather inelegant and Pilkuhn's book is no exception. The notation is often heavy (mostly noncovariant) and the mathematical level rather low. The central topic

  4. Fundamentals of quantum mechanics

    CERN Document Server

    House, J E

    2017-01-01

    Fundamentals of Quantum Mechanics, Third Edition is a clear and detailed introduction to quantum mechanics and its applications in chemistry and physics. All required math is clearly explained, including intermediate steps in derivations, and concise review of the math is included in the text at appropriate points. Most of the elementary quantum mechanical models-including particles in boxes, rigid rotor, harmonic oscillator, barrier penetration, hydrogen atom-are clearly and completely presented. Applications of these models to selected “real world” topics are also included. This new edition includes many new topics such as band theory and heat capacity of solids, spectroscopy of molecules and complexes (including applications to ligand field theory), and small molecules of astrophysical interest.

  5. Fundamentals of quantum mechanics

    CERN Document Server

    Erkoc, Sakir

    2006-01-01

    HISTORICAL EXPERIMENTS AND THEORIESDates of Important Discoveries and Events Blackbody RadiationPhotoelectrice Effect Quantum Theory of Spectra TheComptone Effect Matterwaves, the de Broglie HypothesisThe Davisson -Germer Experiment Heisenberg's Uncertainity PrincipleDifference Between Particles and Waves Interpretation of the Wavefunction AXIOMATIC STRUCTURE OF QUANTUM MECHANICSThe Necessity of Quantum TheoryFunction Spaces Postulates of Quantum Mechanics The Kronecker Delta and the Dirac Delta Function Dirac Notation OBSERVABLES AND SUPERPOSITIONFree Particle Particle In A Box Ensemble Average Hilbert -Space Interpretation The Initial Square Wave Particle Beam Superposition and Uncertainty Degeneracy of States Commutators and Uncertainty TIME DEVELOPMENT AND CONSERVATION THEOREMSTime Development of State Functions, The Discrete Case The Continuous Case, Wave Packets Particle Beam Gaussian Wave Packet Free Particle Propagator The Limiting Cases of the Gaussian Wave Packets Time Development of Expectation Val...

  6. Quantum mechanics selected topics

    CERN Document Server

    Perelomov, Askold Mikhailovich

    1998-01-01

    It can serve as a good supplement to any quantum mechanics textbook, filling the gap between standard textbooks and higher-level books on the one hand and journal articles on the other. This book provides a detailed treatment of the scattering theory, multidimensional quasi-classical approximation, non-stationary problems for oscillators and the theory of unstable particles. It will be useful for postgraduate students and researchers who wish to find new, interesting information hidden in the depths of non-relativistic quantum mechanics.

  7. Noncommutative quantum mechanics

    Science.gov (United States)

    Gamboa, J.; Loewe, M.; Rojas, J. C.

    2001-09-01

    A general noncommutative quantum mechanical system in a central potential V=V(r) in two dimensions is considered. The spectrum is bounded from below and, for large values of the anticommutative parameter θ, we find an explicit expression for the eigenvalues. In fact, any quantum mechanical system with these characteristics is equivalent to a commutative one in such a way that the interaction V(r) is replaced by V=V(HHO,Lz), where HHO is the Hamiltonian of the two-dimensional harmonic oscillator and Lz is the z component of the angular momentum. For other finite values of θ the model can be solved by using perturbation theory.

  8. Elementary quantum mechanics

    CERN Document Server

    Saxon, David S

    2012-01-01

    Based on lectures for an undergraduate UCLA course in quantum mechanics, this volume focuses on the formulas of quantum mechanics rather than applications. Widely used in both upper-level undergraduate and graduate courses, it offers a broad self-contained survey rather than in-depth treatments.Topics include the dual nature of matter and radiation, state functions and their interpretation, linear momentum, the motion of a free particle, Schrödinger's equation, approximation methods, angular momentum, and many other subjects. In the interests of keeping the mathematics as simple as possible, m

  9. Time Asymmetric Quantum Mechanics

    Directory of Open Access Journals (Sweden)

    Arno R. Bohm

    2011-09-01

    Full Text Available The meaning of time asymmetry in quantum physics is discussed. On the basis of a mathematical theorem, the Stone-von Neumann theorem, the solutions of the dynamical equations, the Schrödinger equation (1 for states or the Heisenberg equation (6a for observables are given by a unitary group. Dirac kets require the concept of a RHS (rigged Hilbert space of Schwartz functions; for this kind of RHS a mathematical theorem also leads to time symmetric group evolution. Scattering theory suggests to distinguish mathematically between states (defined by a preparation apparatus and observables (defined by a registration apparatus (detector. If one requires that scattering resonances of width Γ and exponentially decaying states of lifetime τ=h/Γ should be the same physical entities (for which there is sufficient evidence one is led to a pair of RHS's of Hardy functions and connected with it, to a semigroup time evolution t_0≤t<∞, with the puzzling result that there is a quantum mechanical beginning of time, just like the big bang time for the universe, when it was a quantum system. The decay of quasi-stable particles is used to illustrate this quantum mechanical time asymmetry. From the analysis of these processes, we show that the properties of rigged Hilbert spaces of Hardy functions are suitable for a formulation of time asymmetry in quantum mechanics.

  10. Facets of contextual realism in quantum mechanics

    International Nuclear Information System (INIS)

    Pan, Alok Kumar; Home, Dipankar

    2011-01-01

    In recent times, there is an upsurge of interest in demonstrating the quantum contextuality. In this proceedings, we explore the two different forms of arguments that have been used for showing the contextual character of quantum mechanics. First line of study concerns the violations of the noncontextual realist models by quantum mechanics, where second line of study that is qualitatively distinct from the earlier one, demonstrates the contextuality within the formalism of quantum mechanics.

  11. Insights into the catalytic mechanism of dehydrogenase BphB: A quantum mechanics/molecular mechanics study.

    Science.gov (United States)

    Zhang, Ruiming; Shi, Xiangli; Sun, Yanhui; Zhang, Qingzhu; Wang, Wenxing

    2018-05-17

    The present study delineated the dehydrogenation mechanism of cis-2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DDBPH) and cis-2,3-dihydro-2,3-dihydroxy-4,4'-dichlorobiphenyl (2,3-DD-4,4'-DBPH) by Pandoraea pnomenusa strain B-356 cis-2,3-dihydro-2,3-dihydroxybiphenyl dehydrogenase (BphB) in atomistic detail. The enzymatic process was investigated by a combined quantum mechanics/molecular mechanics (QM/MM) approach. Five different snapshots were extracted and calculated, which revealed that the Boltzmann-weighted average barriers of 2,3-DDBPH and 2,3-DD-4,4'-DBPH dehydrogenation processes are 10.7 and 11.5 kcal mol -1 , respectively. The established dehydrogenation mechanism provides new insight into the degradation processes of other chlorinated 2,3-DDBPH. In addition to Asn115, Ser142, and Lys149, the importance of Ile 89, Asn143, Pro184, Met 187, Thr189, and Lue 191 during the dehydrogenation process of 2,3-DDBPH and 2,3-DD-4,4'-DBPH were also highlighted to search for promising mutation targets for improving the catalytic efficiency of BphB. Copyright © 2018. Published by Elsevier Ltd.

  12. Performance assessment of semiempirical molecular orbital methods in describing halogen bonding: quantum mechanical and quantum mechanical/molecular mechanical-molecular dynamics study.

    Science.gov (United States)

    Ibrahim, Mahmoud A A

    2011-10-24

    The performance of semiempirical molecular-orbital methods--MNDO, MNDO-d, AM1, RM1, PM3 and PM6--in describing halogen bonding was evaluated, and the results were compared with molecular mechanical (MM) and quantum mechanical (QM) data. Three types of performance were assessed: (1) geometrical optimizations and binding energy calculations for 27 halogen-containing molecules complexed with various Lewis bases (Two of the tested methods, AM1 and RM1, gave results that agree with the QM data.); (2) charge distribution calculations for halobenzene molecules, determined by calculating the solvation free energies of the molecules relative to benzene in explicit and implicit generalized Born (GB) solvents (None of the methods gave results that agree with the experimental data.); and (3) appropriateness of the semiempirical methods in the hybrid quantum-mechanical/molecular-mechanical (QM/MM) scheme, investigated by studying the molecular inhibition of CK2 protein by eight halobenzimidazole and -benzotriazole derivatives using hybrid QM/MM molecular-dynamics (MD) simulations with the inhibitor described at the QM level by the AM1 method and the rest of the system described at the MM level. The pure MM approach with inclusion of an extra point of positive charge on the halogen atom approach gave better results than the hybrid QM/MM approach involving the AM1 method. Also, in comparison with the pure MM-GBSA (generalized Born surface area) binding energies and experimental data, the calculated QM/MM-GBSA binding energies of the inhibitors were improved by replacing the G(GB,QM/MM) solvation term with the corresponding G(GB,MM) term.

  13. Quantum chemical study of the mechanisms of oxidation of ethylene ...

    Indian Academy of Sciences (India)

    lanl2tz basis set.32–36. Spartan uses a graphical model builder for input preparation. Molecules were constructed and mini- mized interactively using an appropriate molecular mechanics force field. All structural optimizations were done without symmetry restrictions. Normal mode analysis was performed to verify the nature ...

  14. Quantum mechanics over sets

    Science.gov (United States)

    Ellerman, David

    2014-03-01

    In models of QM over finite fields (e.g., Schumacher's ``modal quantum theory'' MQT), one finite field stands out, Z2, since Z2 vectors represent sets. QM (finite-dimensional) mathematics can be transported to sets resulting in quantum mechanics over sets or QM/sets. This gives a full probability calculus (unlike MQT with only zero-one modalities) that leads to a fulsome theory of QM/sets including ``logical'' models of the double-slit experiment, Bell's Theorem, QIT, and QC. In QC over Z2 (where gates are non-singular matrices as in MQT), a simple quantum algorithm (one gate plus one function evaluation) solves the Parity SAT problem (finding the parity of the sum of all values of an n-ary Boolean function). Classically, the Parity SAT problem requires 2n function evaluations in contrast to the one function evaluation required in the quantum algorithm. This is quantum speedup but with all the calculations over Z2 just like classical computing. This shows definitively that the source of quantum speedup is not in the greater power of computing over the complex numbers, and confirms the idea that the source is in superposition.

  15. Supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Crombrugghe, M. de; Rittenberg, V.

    1982-12-01

    We give a general construction for supersymmetric Hamiltonians in quantum mechanics. We find that N-extended supersymmetry imposes very strong constraints, and for N > 4 the Hamiltonian is integrable. We give a variety of examples, for one-particle and for many-particle systems, in different numbers of dimensions. (orig.)

  16. Kowalevski top in quantum mechanics

    International Nuclear Information System (INIS)

    Matsuyama, A.

    2013-01-01

    The quantum mechanical Kowalevski top is studied by the direct diagonalization of the Hamiltonian. The spectra show different behaviors depending on the region divided by the bifurcation sets of the classical invariant tori. Some of these spectra are nearly degenerate due to the multiplicity of the invariant tori. The Kowalevski top has several symmetries and symmetry quantum numbers can be assigned to the eigenstates. We have also carried out the semiclassical quantization of the Kowalevski top by the EBK formulation. It is found that the semiclassical spectra are close to the exact values, thus the eigenstates can be also labeled by the integer quantum numbers. The symmetries of the system are shown to have close relations with the semiclassical quantum numbers and the near-degeneracy of the spectra. -- Highlights: •Quantum spectra of the Kowalevski top are calculated. •Semiclassical quantization is carried out by the EBK formulation. •Quantum states are labeled by the semiclassical integer quantum numbers. •Multiplicity of the classical torus makes the spectra nearly degenerate. •Symmetries, quantum numbers and near-degenerate spectra are closely related

  17. Relational quantum mechanics

    International Nuclear Information System (INIS)

    Rovelli, C.

    1996-01-01

    I suggest that the common unease with taking quantum mechanics as a fundamental description of nature (the open-quotes measurement problemclose quotes) could derive from the use of an incorrect notion, as the unease with the Lorentz transformations before Einstein derived from the notion of observer-independent time. I suggest that this incorrect notion that generates the unease with quantum mechanics is the notion of open-quotes observer-independent stateclose quotes of a system, or open-quotes observer-independent values of physical quantities.close quotes I reformulate the problem of the open-quotes interpretation of quantum mechanicsclose quotes as the problem of deriving the formalism from a set of simple physical postulates. I consider a reformulation of quantum mechanics in terms of information theory. All systems are assumed to be equivalent, there is no observer-observed distinction, and the theory describes only the information that systems have about each other; nevertheless, the theory is complete

  18. The essentials of quantum mechanics

    International Nuclear Information System (INIS)

    Omnes, R.

    2006-09-01

    This book is an introduction to quantum mechanics, the author explains the foundation, interpretation and today limits of this science. The consequences of quantum concepts are reviewed through the lens of recent experimental data. In that way, issues like wave-particle duality, uncertainty principle, decoherence, relationship with classical mechanics or the unicity of reality, issues that were difficult to grasp before, appear now clearer. The book has been divided into 8 chapters: 1) possibility and chance, 2) quantum formalism, 3) fundamental quantum concepts, 4) how to deal with quantum mechanics, 5) decoherence theory, 6) the quantum logic system, 7) the emergence of classical physics, and 8) quantum measurements. (A.C.)

  19. Renormalisation in Quantum Mechanics, Quantum Instantons and Quantum Chaos

    OpenAIRE

    Jirari, H.; Kröger, H.; Luo, X. Q.; Moriarty, K. J. M.

    2001-01-01

    We suggest how to construct non-perturbatively a renormalized action in quantum mechanics. We discuss similarties and differences with the standard effective action. We propose that the new quantum action is suitable to define and compute quantum instantons and quantum chaos.

  20. Quantum mechanics and electrodynamics

    CERN Document Server

    Zamastil, Jaroslav

    2017-01-01

    This book highlights the power and elegance of algebraic methods of solving problems in quantum mechanics. It shows that symmetries not only provide elegant solutions to problems that can be solved exactly, but also substantially simplify problems that must be solved approximately. Furthermore, the book provides an elementary exposition of quantum electrodynamics and its application to low-energy physics, along with a thorough analysis of the role of relativistic, magnetic, and quantum electrodynamic effects in atomic spectroscopy. Included are essential derivations made clear through detailed, transparent calculations. The book’s commitment to deriving advanced results with elementary techniques, as well as its inclusion of exercises will enamor it to advanced undergraduate and graduate students.

  1. A quantum mechanical model of "dark matter"

    OpenAIRE

    Belokurov, V. V.; Shavgulidze, E. T.

    2014-01-01

    The role of singular solutions in some simple quantum mechanical models is studied. The space of the states of two-dimensional quantum harmonic oscillator is shown to be separated into sets of states with different properties.

  2. Concepts in quantum mechanics

    CERN Document Server

    Mathur, Vishnu S

    2008-01-01

    NEED FOR QUANTUM MECHANICS AND ITS PHYSICAL BASIS Inadequacy of Classical Description for Small Systems Basis of Quantum Mechanics Representation of States Dual Vectors: Bra and Ket Vectors Linear Operators Adjoint of a Linear Operator Eigenvalues and Eigenvectors of a Linear Operator Physical Interpretation Observables and Completeness Criterion Commutativity and Compatibility of Observables Position and Momentum Commutation Relations Commutation Relation and the Uncertainty ProductAppendix: Basic Concepts in Classical MechanicsREPRESENTATION THEORY Meaning of Representation How to Set up a Representation Representatives of a Linear Operator Change of Representation Coordinate Representation Replacement of Momentum Observable p by -ih d/dqIntegral Representation of Dirac Bracket A2|F|A1> The Momentum Representation Dirac Delta FunctionRelation between the Coordinate and Momentum RepresentationsEQUATIONS OF MOTIONSchrödinger Equation of Motion Schrödinger Equation in the Coordinate Representation Equation o...

  3. Lattice studies of quark spectra and supersymmetric quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Schierenberg, Sebastian

    2012-06-24

    In the first part of this work, we study quark spectra at either non-zero temperature or chemical potential. In the first case, we find a possible explanation for the Anderson localization that is observed in the spectrum. We introduce a random matrix model that has the same localization and shares other important properties of the QCD Dirac operator, too. In the case of a non-vanishing chemical potential, we show that the eigenvalue spacing distributions of the Dirac operator are described by simple random matrix models. In the second part of this work, we study supersymmetry on the lattice. We summarize our progress with the blocking approach and show possible problems. Furthermore, we construct a lattice action which is improved with respect to supersymmetry and study this action numerically.

  4. Lattice studies of quark spectra and supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Schierenberg, Sebastian

    2012-01-01

    In the first part of this work, we study quark spectra at either non-zero temperature or chemical potential. In the first case, we find a possible explanation for the Anderson localization that is observed in the spectrum. We introduce a random matrix model that has the same localization and shares other important properties of the QCD Dirac operator, too. In the case of a non-vanishing chemical potential, we show that the eigenvalue spacing distributions of the Dirac operator are described by simple random matrix models. In the second part of this work, we study supersymmetry on the lattice. We summarize our progress with the blocking approach and show possible problems. Furthermore, we construct a lattice action which is improved with respect to supersymmetry and study this action numerically.

  5. A Practical Quantum Mechanics Molecular Mechanics Method for the Dynamical Study of Reactions in Biomolecules.

    Science.gov (United States)

    Mendieta-Moreno, Jesús I; Marcos-Alcalde, Iñigo; Trabada, Daniel G; Gómez-Puertas, Paulino; Ortega, José; Mendieta, Jesús

    2015-01-01

    Quantum mechanics/molecular mechanics (QM/MM) methods are excellent tools for the modeling of biomolecular reactions. Recently, we have implemented a new QM/MM method (Fireball/Amber), which combines an efficient density functional theory method (Fireball) and a well-recognized molecular dynamics package (Amber), offering an excellent balance between accuracy and sampling capabilities. Here, we present a detailed explanation of the Fireball method and Fireball/Amber implementation. We also discuss how this tool can be used to analyze reactions in biomolecules using steered molecular dynamics simulations. The potential of this approach is shown by the analysis of a reaction catalyzed by the enzyme triose-phosphate isomerase (TIM). The conformational space and energetic landscape for this reaction are analyzed without a priori assumptions about the protonation states of the different residues during the reaction. The results offer a detailed description of the reaction and reveal some new features of the catalytic mechanism. In particular, we find a new reaction mechanism that is characterized by the intramolecular proton transfer from O1 to O2 and the simultaneous proton transfer from Glu 165 to C2. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. p-Adic quantum mechanics

    International Nuclear Information System (INIS)

    Vladimirov, V.S.; Volovich, I.V.

    1988-01-01

    Quantum mechanics above the field of p-adic numbers is constructed. Three formulations of p-adic quantum mechanics are considered: 1) quantum mechanics with complex-valued wave functions and p-adic coordinates and pulses; an approach based on Weyl representation is suggested; 2) the probability (Euclidean) formulation; 3) the secondary quantization representation (Fock representation) with p-adic wave functions

  7. Quantum mechanics. 2. printing (paperback).

    International Nuclear Information System (INIS)

    Lipkin, H.J.

    1986-01-01

    Intended for a first year graduate course in quantum mechanics, this collection of topics can also be considered as a set of self-contained 'monographs for pedestrians' on the Moessbauer effect, many-body quantum mechanics, kaon physics, scattering theory, Feynman diagrams, symmetries and relativistic quantum mechanics. (Auth.)

  8. Symmetry and quantum mechanics

    CERN Document Server

    Corry, Scott

    2016-01-01

    This book offers an introduction to quantum mechanics for professionals, students, and others in the field of mathematics who have a minimal background in physics with an understanding of linear algebra and group theory. It covers such topics as Lie groups, algebras and their representations, and analysis (Hilbert space, distributions, the spectral Theorem, and the Stone-Von Neumann Theorem). The book emphasizes the role of symmetry and is useful to physicists as it provides a mathematical introduction to the topic.

  9. Supersymmetry in quantum mechanics

    International Nuclear Information System (INIS)

    Lahiri, A.; Roy, P.K.; Bagghi, B.

    1990-01-01

    A pedagogical review on supersymmetry in quantum mechanics is presented which provides a comprehensive coverage of the subject. First, the key ingredients of the quantization of the systems with anticommuting variables are discussed. The supersymmetric Hamiltonian in quantum mechanics is then constructed by emphasizing the role of partner potentials and the superpotentials. The authors also make explicit the mathematical formulation of the Hamiltonian by considering in detail the N = 1 and N = 2 supersymmetric (quantum) mechanics. Supersymmetry is then discussed in the context of one-dimensional problems and the importance of the factorization method is highlighted. They treat in detail the technique of constructing a hierarchy of Hamiltonians employing the so-called 'shape-invariance' of potentials. To make transparent the relationship between supersymmetry and solvable potentials, they also solve several examples. They then go over the formulation of supersymmetry in radial problems, paying a special attention to the Coulomb and isotropic oscillator potentials. They show that the ladder operator technique may be suitable modified in higher dimensions for generating isospectral Hamiltonians. Next, the criteria for the breaking of supersymmetry is considered and their range of applicability is examined by suitably modifying he definition of Witten's index. Finally, the authors perform some numerical calculations for a class of potentials to show how a modified WKB approximation works in supersymmetric cases

  10. Quantum Mechanics and Molecular Mechanics Study of the Catalytic Mechanism of Human AMSH-LP Domain Deubiquitinating Enzymes.

    Science.gov (United States)

    Zhu, Wenyou; Liu, Yongjun; Ling, Baoping

    2015-08-25

    Deubiquitinating enzymes (DUBs) catalyze the cleavage of the isopeptide bond in polyubiquitin chains to control and regulate the deubiquitination process in all known eukaryotic cells. The human AMSH-LP DUB domain specifically cleaves the isopeptide bonds in the Lys63-linked polyubiquitin chains. In this article, the catalytic mechanism of AMSH-LP has been studied using a combined quantum mechanics and molecular mechanics method. Two possible hydrolysis processes (Path 1 and Path 2) have been considered. Our calculation results reveal that the activation of Zn(2+)-coordinated water molecule is the essential step for the hydrolysis of isopeptide bond. In Path 1, the generated hydroxyl first attacks the carbonyl group of Gly76, and then the amino group of Lys63 is protonated, which is calculated to be the rate limiting step with an energy barrier of 13.1 kcal/mol. The energy barrier of the rate limiting step and the structures of intermediate and product are in agreement with the experimental results. In Path 2, the protonation of amino group of Lys63 is prior to the nucleophilic attack of activated hydroxyl. The two proton transfer processes in Path 2 correspond to comparable overall barriers (33.4 and 36.1 kcal/mol), which are very high for an enzymatic reaction. Thus, Path 2 can be ruled out. During the reaction, Glu292 acts as a proton transfer mediator, and Ser357 mainly plays a role in stabilizing the negative charge of Gly76. Besides acting as a Lewis acid, Zn(2+) also influences the reaction by coordinating to the reaction substrates (W1 and Gly76).

  11. QUANTUM MECHANICS. Quantum squeezing of motion in a mechanical resonator.

    Science.gov (United States)

    Wollman, E E; Lei, C U; Weinstein, A J; Suh, J; Kronwald, A; Marquardt, F; Clerk, A A; Schwab, K C

    2015-08-28

    According to quantum mechanics, a harmonic oscillator can never be completely at rest. Even in the ground state, its position will always have fluctuations, called the zero-point motion. Although the zero-point fluctuations are unavoidable, they can be manipulated. Using microwave frequency radiation pressure, we have manipulated the thermal fluctuations of a micrometer-scale mechanical resonator to produce a stationary quadrature-squeezed state with a minimum variance of 0.80 times that of the ground state. We also performed phase-sensitive, back-action evading measurements of a thermal state squeezed to 1.09 times the zero-point level. Our results are relevant to the quantum engineering of states of matter at large length scales, the study of decoherence of large quantum systems, and for the realization of ultrasensitive sensing of force and motion. Copyright © 2015, American Association for the Advancement of Science.

  12. Modern logic and quantum mechanics

    International Nuclear Information System (INIS)

    Garden, R.W.

    1984-01-01

    The book applies the methods of modern logic and probabilities to ''interpreting'' quantum mechanics. The subject is described and discussed under the chapter headings: classical and quantum mechanics, modern logic, the propositional logic of mechanics, states and measurement in mechanics, the traditional analysis of probabilities, the probabilities of mechanics and the model logic of predictions. (U.K.)

  13. Study on linear canonical transformation in a framework of a phase space representation of quantum mechanics

    International Nuclear Information System (INIS)

    Raoelina Andriambololona; Ranaivoson, R.T.R.; Rakotoson, H.; Solofoarisina, W.C.

    2015-04-01

    We present a study on linear canonical transformation in the framework of a phase space representation of quantum mechanics that we have introduced in our previous work. We begin with a brief recall about the so called phase space representation. We give the definition of linear canonical transformation with the transformation law of coordinate and momentum operators. We establish successively the transformation laws of mean values, dispersions, basis state and wave functions.Then we introduce the concept of isodispersion linear canonical transformation.

  14. Quantum-Mechanical Particle Confined to Surfaces of Revolution - Truncated Cone and Elliptic Torus Case Studies

    DEFF Research Database (Denmark)

    Gravesen, Jens; Willatzen, Morten; Voon, L.C. Lew Yan

    2005-01-01

    The theory of a quantum-mechanical particle confined to a surface of revolution is described using differential geometry methods including the derivation of a general set of three ordinary differential equations in curved coordinates. The problem is shown to be completely separable with the present...... hard-wall boundary conditions. Two case studies of recent experimental interest. the nanocone and torus-shaped nanoring structures. are analyzed in terms of eigenstates, energies. and symmetry characteristics based on the theory presented....

  15. Lectures on Quantum Mechanics

    CERN Document Server

    Basdevant, Jean-Louis

    2007-01-01

    Beautifully illustrated and engagingly written, Lectures on Quantum Mechanics presents theoretical physics with a breathtaking array of examples and anecdotes. Basdevant's style is clear and stimulating, in the manner of a brisk classroom lecture that students can follow with ease and enjoyment. Here is a sample of the book's style, from the opening of Chapter 1: "If one were to ask a passer-by to quote a great formula of physics, chances are that the answer would be 'E = mc2'. Nevertheless, the formula 'E=hV' which was written in the same year 1905 by the same Albert Einstein, and which started quantum theory, concerns their daily life considerably more. In fact, of the three watershed years for physics toward the beginning of the 20th century - 1905: the Special Relativity of Einstein, Lorentz and Poincaré; 1915: the General Relativity of Einstein, with its extraordinary reflections on gravitation, space and time; and 1925: the full development of Quantum Mechanics - it is surely the last which has the mos...

  16. Supersymmetric quantum mechanics: another nontrivial quantum superpotential

    International Nuclear Information System (INIS)

    Cervero, J.M.

    1991-01-01

    A nontrivial example of a quantum superpotential in the framework of supersymmetric quantum mechanics is constructed using integrable soliton-like functions. The model is shown to be fully solvable and some consequences regarding the physical properties of the model such as transparence and boundary effects are discussed. (orig.)

  17. Bananaworld quantum mechanics for primates

    CERN Document Server

    Bub, Jeffrey

    2016-01-01

    What on earth do bananas have to do with quantum mechanics? From a modern perspective, quantum mechanics is about strangely counterintuitive correlations between separated systems, which can be exploited in feats like quantum teleportation, unbreakable cryptographic schemes, and computers with enormously enhanced computing power. Schro?dinger coined the term "entanglement" to describe these bizarre correlations. Bananaworld -- an imaginary island with "entangled" bananas -- brings to life the fascinating discoveries of the new field of quantum information without the mathematical machinery of quantum mechanics. The connection with quantum correlations is fully explained in sections written for the non-physicist reader with a serious interest in understanding the mysteries of the quantum world. The result is a subversive but entertaining book that is accessible and interesting to a wide range of readers, with the novel thesis that quantum mechanics is about the structure of information. What we have discovered...

  18. Operator methods in quantum mechanics

    CERN Document Server

    Schechter, Martin

    2003-01-01

    This advanced undergraduate and graduate-level text introduces the power of operator theory as a tool in the study of quantum mechanics, assuming only a working knowledge of advanced calculus and no background in physics. The author presents a few simple postulates describing quantum theory, gradually introducing the mathematical techniques that help answer questions important to the physical theory; in this way, readers see clearly the purpose of the method and understand the accomplishment. The entire book is devoted to the study of a single particle moving along a straight line. By posing q

  19. Emergent mechanics, quantum and un-quantum

    Science.gov (United States)

    Ralston, John P.

    2013-10-01

    There is great interest in quantum mechanics as an "emergent" phenomenon. The program holds that nonobvious patterns and laws can emerge from complicated physical systems operating by more fundamental rules. We find a new approach where quantum mechanics itself should be viewed as an information management tool not derived from physics nor depending on physics. The main accomplishment of quantum-style theory comes in expanding the notion of probability. We construct a map from macroscopic information as data" to quantum probability. The map allows a hidden variable description for quantum states, and efficient use of the helpful tools of quantum mechanics in unlimited circumstances. Quantum dynamics via the time-dependent Shroedinger equation or operator methods actually represents a restricted class of classical Hamiltonian or Lagrangian dynamics, albeit with different numbers of degrees of freedom. We show that under wide circumstances such dynamics emerges from structureless dynamical systems. The uses of the quantum information management tools are illustrated by numerical experiments and practical applications

  20. Quantum mechanical resonances

    International Nuclear Information System (INIS)

    Cisneros S, A.; McIntosh, H.V.

    1982-01-01

    A discussion of the nature of quantum mechanical resonances is presented from the point of view of the spectral theory of operators. In the case of Bohr-Feshbach resonances, graphs are presented to illustrate the theory showing the decay of a doubly excited metastable state and the excitation of the resonance by an incident particle with proper energy. A characterization of resonances is given as well as a procedure to determine widths using the spectral density function. A sufficient condition is given for the validity of the Breit-Wigner formula for Bohr-Feshbach resonances. (author)

  1. Unwaving quantum mechanics

    International Nuclear Information System (INIS)

    Torre, A.C. de la; Mirabella, D.; Izus, G.

    1990-01-01

    The so called diffraction experiments are explained making no reference to any wave whatsoever. It is proposed that these waves are a mere mathematical artifact without any physical reality. If propensities and transmission between them are accepted as a physical reality, then the wave concept can be set aside along with duality and complementarity, thus eliminating controversy on the interpretation of quantum mechanics. An outline is made of the formulation of the theory based on the preparation of the system according to propensities and the transmission between them. (Author). 19 refs., 1 fig

  2. Classical Mechanics as Nonlinear Quantum Mechanics

    International Nuclear Information System (INIS)

    Nikolic, Hrvoje

    2007-01-01

    All measurable predictions of classical mechanics can be reproduced from a quantum-like interpretation of a nonlinear Schroedinger equation. The key observation leading to classical physics is the fact that a wave function that satisfies a linear equation is real and positive, rather than complex. This has profound implications on the role of the Bohmian classical-like interpretation of linear quantum mechanics, as well as on the possibilities to find a consistent interpretation of arbitrary nonlinear generalizations of quantum mechanics

  3. Case study of a successful learner's epistemological framings of quantum mechanics

    Science.gov (United States)

    Dini, Vesal; Hammer, David

    2017-06-01

    Research on student epistemologies in introductory courses has highlighted the importance of understanding physics as "a refinement of everyday thinking" [A. Einstein, J. Franklin Inst. 221, 349 (1936), 10.1016/S0016-0032(36)91047-5]. That view is difficult to sustain in quantum mechanics, for students as for physicists. How might students manage the transition? In this article, we present a case study of a graduate student's approaches and reflections on learning over two semesters of quantum mechanics, based on a series of nine interviews. We recount his explicit grappling with the shift in epistemology from classical to quantum, and we argue that his success in learning largely involved his framing mathematics as expressing physical meaning. At the same time, we show he was not entirely stable in these framings, shifting away from them in particular during his study of scattering. The case speaks to literature on students' epistemologies, with respect to the roles of everyday thinking and mathematics. We discuss what this case suggests for further research, with possible implications for instruction.

  4. Bell's theorem and quantum mechanics

    Science.gov (United States)

    Rosen, Nathan

    1994-02-01

    Bell showed that assuming locality leads to a disagreement with quantum mechanics. Here the nature of the nonlocality that follows from quantum mechanics is investigated. Note by the Editor—Readers will recognize Professor Rosen, author of this paper, as one of the co-authors of the famous EPR paper, Albert Einstein, Boris Podolsky, and Nathan Rosen, ``Can Quantum-Mechanical Description of Physical Reality be considered Complete?'', Phys. Rev. 47, 770-780 (1935). Robert H. Romer, Editor

  5. Quantum mechanics and Bell's inequalities

    International Nuclear Information System (INIS)

    Jones, R.T.; Adelberger, E.G.

    1994-01-01

    Santos argues that, if one interprets probabilities as ratios of detected events to copies of the physical system initially prepared, the quantum mechanical predictions for the classic tests of Bell's inequalities do not violate the inequalities. Furthermore, he suggests that quantum mechanical states which do violate the inequalities are not physically realizable. We discuss a physically realizable experiment, meeting his requirements, where quantum mechanics does violate the inequalities

  6. A textbook of quantum mechanics

    International Nuclear Information System (INIS)

    Mathews, P.M.; Venkatesan, K.

    1977-01-01

    After briefly surveying the inadequacy of the classical ideas and elementary older quantum theory, the ideas of wave mechanics, the postulates of quantum mechanics, exactly soluble problems, approximation techniques, scattering theory, angular momentum, time dependent problems and the basic ideas of relativistic quantum mechanics are discussed. The book is meant for the Master of Science degree course students of Indian Universities. (M.G.B.)

  7. QUANTUM MECHANICAL STUDY OF THE COMPETITIVE HYDRATION BETWEEN PROTONATED QUINAZOLINE AND LI+, NA+, AND CA2+ IONS

    Science.gov (United States)

    Hydration reactions are fundamental to many biological functions and environmental processes. The energetics of hydration of inorganic and organic chemical species influences their fate and transport behavior in the environment. In this study, gas-phase quantum mechanical calcula...

  8. Holomorphic anomaly and quantum mechanics

    Science.gov (United States)

    Codesido, Santiago; Mariño, Marcos

    2018-02-01

    We show that the all-orders WKB periods of one-dimensional quantum mechanical oscillators are governed by the refined holomorphic anomaly equations of topological string theory. We analyze in detail the double-well potential and the cubic and quartic oscillators, and we calculate the WKB expansion of their quantum free energies by using the direct integration of the anomaly equations. We reproduce in this way all known results about the quantum periods of these models, which we express in terms of modular forms on the WKB curve. As an application of our results, we study the large order behavior of the WKB expansion in the case of the double well, which displays the double factorial growth typical of string theory.

  9. Statistical ensembles in quantum mechanics

    International Nuclear Information System (INIS)

    Blokhintsev, D.

    1976-01-01

    The interpretation of quantum mechanics presented in this paper is based on the concept of quantum ensembles. This concept differs essentially from the canonical one by that the interference of the observer into the state of a microscopic system is of no greater importance than in any other field of physics. Owing to this fact, the laws established by quantum mechanics are not of less objective character than the laws governing classical statistical mechanics. The paradoxical nature of some statements of quantum mechanics which result from the interpretation of the wave functions as the observer's notebook greatly stimulated the development of the idea presented. (Auth.)

  10. Quantum Mechanics for Electrical Engineers

    CERN Document Server

    Sullivan, Dennis M

    2011-01-01

    The main topic of this book is quantum mechanics, as the title indicates.  It specifically targets those topics within quantum mechanics that are needed to understand modern semiconductor theory.   It begins with the motivation for quantum mechanics and why classical physics fails when dealing with very small particles and small dimensions.  Two key features make this book different from others on quantum mechanics, even those usually intended for engineers:   First, after a brief introduction, much of the development is through Fourier theory, a topic that is at

  11. Conceptual foundations of quantum mechanics

    International Nuclear Information System (INIS)

    Shimony, A.

    1989-01-01

    Radical innovation in the quantum mechanical framework such as objective indefiniteness, objective chance, objective probability, potentiality, entanglement and quantum nonlocality are discussed and related to the standard formalism. Examples are given which though problematic in classical mechanics are simply explained with these new concepts. Evidence is presented that the conceptual innovations of quantum mechanics cannot be separated from its predictive power. Proposals for solving ''the reduction of the wave packet'' anomaly are presented. Further radical innovations in quantum mechanics are anticipated. (U.K.)

  12. Quantum mechanics the theoretical minimum

    CERN Document Server

    Susskind, Leonard

    2014-01-01

    From the bestselling author of The Theoretical Minimum, an accessible introduction to the math and science of quantum mechanicsQuantum Mechanics is a (second) book for anyone who wants to learn how to think like a physicist. In this follow-up to the bestselling The Theoretical Minimum, physicist Leonard Susskind and data engineer Art Friedman offer a first course in the theory and associated mathematics of the strange world of quantum mechanics. Quantum Mechanics presents Susskind and Friedman’s crystal-clear explanations of the principles of quantum states, uncertainty and time dependence, entanglement, and particle and wave states, among other topics. An accessible but rigorous introduction to a famously difficult topic, Quantum Mechanics provides a tool kit for amateur scientists to learn physics at their own pace.

  13. Decoherence in quantum mechanics and quantum cosmology

    Science.gov (United States)

    Hartle, James B.

    1992-01-01

    A sketch of the quantum mechanics for closed systems adequate for cosmology is presented. This framework is an extension and clarification of that of Everett and builds on several aspects of the post-Everett development. It especially builds on the work of Zeh, Zurek, Joos and Zeh, and others on the interactions of quantum systems with the larger universe and on the ideas of Griffiths, Omnes, and others on the requirements for consistent probabilities of histories.

  14. Quantum mechanics and the psyche

    Science.gov (United States)

    Galli Carminati, G.; Martin, F.

    2008-07-01

    In this paper we apply the last developments of the theory of measurement in quantum mechanics to the phenomenon of consciousness and especially to the awareness of unconscious components. Various models of measurement in quantum mechanics can be distinguished by the fact that there is, or there is not, a collapse of the wave function. The passive aspect of consciousness seems to agree better with models in which there is no collapse of the wave function, whereas in the active aspect of consciousness—i.e., that which goes together with an act or a choice—there seems to be a collapse of the wave function. As an example of the second possibility we study in detail the photon delayed-choice experiment and its consequences for subjective or psychological time. We apply this as an attempt to explain synchronicity phenomena. As a model of application of the awareness of unconscious components we study the mourning process. We apply also the quantum paradigm to the phenomenon of correlation at a distance between minds, as well as to group correlations that appear during group therapies or group training. Quantum entanglement leads to the formation of group unconscious or collective unconscious. Finally we propose to test the existence of such correlations during sessions of group training.

  15. A quantum mechanical/molecular mechanical study of the hydroxylation of phenol and halogeneted derivatives by phenol hydroxylase

    NARCIS (Netherlands)

    Ridder, L.; Mulholland, A.J.; Rietjens, I.M.C.M.; Vervoort, J.

    2000-01-01

    A combined quantum mechanical and molecular mechanical (QM/MM) method (AM1/CHARMM) was used to investigate the mechanism of the aromatic hydroxylation of phenol by a flavin dependent phenol hydroxylase (PH), an essential reaction in the degradation of a wide range of aromatic compounds. The model

  16. Quantum mechanics II advanced topics

    CERN Document Server

    Rajasekar, S

    2015-01-01

    Quantum Mechanics II: Advanced Topics uses more than a decade of research and the authors’ own teaching experience to expound on some of the more advanced topics and current research in quantum mechanics. A follow-up to the authors introductory book Quantum Mechanics I: The Fundamentals, this book begins with a chapter on quantum field theory, and goes on to present basic principles, key features, and applications. It outlines recent quantum technologies and phenomena, and introduces growing topics of interest in quantum mechanics. The authors describe promising applications that include ghost imaging, detection of weak amplitude objects, entangled two-photon microscopy, detection of small displacements, lithography, metrology, and teleportation of optical images. They also present worked-out examples and provide numerous problems at the end of each chapter.

  17. Systematic study of imidazoles inhibiting IDO1 via the integration of molecular mechanics and quantum mechanics calculations.

    Science.gov (United States)

    Zou, Yi; Wang, Fang; Wang, Yan; Guo, Wenjie; Zhang, Yihua; Xu, Qiang; Lai, Yisheng

    2017-05-05

    Indoleamine 2,3-dioxygenase 1 (IDO1) is regarded as an attractive target for cancer immunotherapy. To rationalize the detailed interactions between IDO1 and its inhibitors at the atomic level, an integrated computational approach by combining molecular mechanics and quantum mechanics methods was employed in this report. Specifically, the binding modes of 20 inhibitors was initially investigated using the induced fit docking (IFD) protocol, which outperformed other two docking protocols in terms of correctly predicting ligand conformations. Secondly, molecular dynamics (MD) simulations and MM/PBSA free energy calculations were employed to determine the dynamic binding process and crucial residues were confirmed through close contact analysis, hydrogen-bond analysis and binding free energy decomposition calculations. Subsequent quantum mechanics and nonbonding interaction analysis were carried out to provide in-depth explanations on the critical role of those key residues, and Arg231 and 7-propionate of the heme group were major contributors to ligand binding, which lowed a great amount of interaction energy. We anticipate that these findings will be valuable for enzymatic studies and rational drug design. Copyright © 2017. Published by Elsevier Masson SAS.

  18. Insights into the Reaction Mechanism of Aromatic Ring Cleavage by Homogentisate Dioxygenase: A Quantum Mechanical/Molecular Mechanical Study.

    Science.gov (United States)

    Qi, Yue; Lu, Jiarui; Lai, Wenzhen

    2016-05-26

    To elucidate the reaction mechanism of the ring cleavage of homogentisate by homogentisate dioxygenase, quantum mechanical/molecular mechanical (QM/MM) calculations were carried out by using two systems in different protonation states of the substrate C2 hydroxyl group. When the substrate C2 hydroxyl group is ionized (the ionized pathway), the superoxo attack on the substrate is the rate-limiting step in the catalytic cycle, with a barrier of 15.9 kcal/mol. Glu396 was found to play an important role in stabilizing the bridge species and its O-O cleavage product by donating a proton via a hydrogen-bonded water molecule. When the substrate C2 hydroxyl group is not ionized (the nonionized pathway), the O-O bond cleavage of the bridge species is the rate-limiting step, with a barrier of 15.3 kcal/mol. The QM/MM-optimized geometries for the dioxygen and alkylperoxo complexes using the nonionized model (for the C2 hydroxyl group) are in agreement with the experimental crystal structures, suggesting that the C2 hydroxyl group is more likely to be nonionized.

  19. Introduction to quantum statistical mechanics

    International Nuclear Information System (INIS)

    Bogolyubov, N.N.; Bogolyubov, N.N.

    1980-01-01

    In a set of lectures, which has been delivered at the Physical Department of Moscow State University as a special course for students represented are some basic ideas of quantum statistical mechanics. Considered are in particular, the Liouville equations in classical and quantum mechanics, canonical distribution and thermodynamical functions, two-time correlation functions and Green's functions in the theory of thermal equilibrium

  20. Quantum mechanics & the big world

    NARCIS (Netherlands)

    Wezel, Jasper van

    2007-01-01

    Quantum Mechanics is one of the most successful physical theories of the last century. It explains physical phenomena from the smallest to the largest lengthscales. Despite this triumph, quantum mechanics is often perceived as a mysterious theory, involving superposition states that are alien to our

  1. QUANTUM MECHANICS WITHOUT STATISTICAL POSTULATES

    International Nuclear Information System (INIS)

    Geiger, G.

    2000-01-01

    The Bohmian formulation of quantum mechanics describes the measurement process in an intuitive way without a reduction postulate. Due to the chaotic motion of the hidden classical particle all statistical features of quantum mechanics during a sequence of repeated measurements can be derived in the framework of a deterministic single system theory

  2. Quantum mechanics and its limits

    International Nuclear Information System (INIS)

    Lamehi-Rachti, M.; Mittig, W.

    1977-01-01

    Bell has shown (Bell's inequality) that local hidden variable theories lead to predictions in contradiction with quantum mechanics. This has been tested in low energy proton-proton scattering by the simultaneous measurement of the polarisation of the two protons. The results are in agreement with quantum mechanics and thus in contradiction with the inequality of Bell [fr

  3. Foundations of Quantum Mechanics and Quantum Computation

    Science.gov (United States)

    Aspect, Alain; Leggett, Anthony; Preskill, John; Durt, Thomas; Pironio, Stefano

    2013-03-01

    I ask the question: What can we infer about the nature and structure of the physical world (a) from experiments already done to test the predictions of quantum mechanics (b) from the assumption that all future experiments will agree with those predictions? I discuss existing and projected experiments related to the two classic paradoxes of quantum mechanics, named respectively for EPR and Schrödinger's Cat, and show in particular that one natural conclusion from both types of experiment implies the abandonment of the concept of macroscopic counterfactual definiteness.

  4. On Galilean covariant quantum mechanics

    International Nuclear Information System (INIS)

    Horzela, A.; Kapuscik, E.; Kempczynski, J.; Joint Inst. for Nuclear Research, Dubna

    1991-08-01

    Formalism exhibiting the Galilean covariance of wave mechanics is proposed. A new notion of quantum mechanical forces is introduced. The formalism is illustrated on the example of the harmonic oscillator. (author)

  5. Quantum mechanics a fundamental approach

    CERN Document Server

    Wan, K Kong

    2018-01-01

    The mathematical formalism of quantum theory in terms of vectors and operators in infinite-dimensional complex vector spaces is very abstract. The definitions of many mathematical quantities used do not seem to have an intuitive meaning. This makes it difficult to appreciate the mathematical formalism and hampers the understanding of quantum mechanics. This book provides intuition and motivation to the mathematics of quantum theory, introducing the mathematics in its simplest and familiar form, for instance, with three-dimensional vectors and operators, which can be readily understood. Feeling confident about and comfortable with the mathematics used helps readers appreciate and understand the concepts and formalism of quantum mechanics. Quantum mechanics is presented in six groups of postulates. A chapter is devoted to each group of postulates with a detailed discussion. Systems with superselection rules, and some conceptual issues such as quantum paradoxes and measurement, are also discussed. The book conc...

  6. Logical foundation of quantum mechanics

    International Nuclear Information System (INIS)

    Stachow, E.W.

    1980-01-01

    The subject of this article is the reconstruction of quantum mechanics on the basis of a formal language of quantum mechanical propositions. During recent years, research in the foundations of the language of science has given rise to a dialogic semantics that is adequate in the case of a formal language for quantum physics. The system of sequential logic which is comprised by the language is more general than classical logic; it includes the classical system as a special case. Although the system of sequential logic can be founded without reference to the empirical content of quantum physical propositions, it establishes an essential part of the structure of the mathematical formalism used in quantum mechanics. It is the purpose of this paper to demonstrate the connection between the formal language of quantum physics and its representation by mathematical structures in a self-contained way. (author)

  7. Study of the equations of a particle in Non- Relativistic Quantum Mechanics

    International Nuclear Information System (INIS)

    Miltao, Milton Souza Ribeiro; Silva, Vanessa Santos Teles da

    2011-01-01

    Full text: The study of group theory is relevant to the treatment of physical problems, in which concepts of invariance and symmetry are important. In the field of Non-Relativistic Quantum Mechanics, we can do algebraic considerations taking into account the principles of symmetry, considering the framework of the study of Galileo transformations, which have characteristics of group. Therefore, we discuss the Stern-Gerlach experiment that had the historical importance of demonstrating that the electron has an intrinsic angular momentum. Through discussion of this experiment, we found that the spin appears in Non-Relativistic Quantum Mechanics as a feature of the algebraic structure underlying any physical theory represented by a group. From these studies, we have algebraic considerations for physical systems in non-relativistic domain, which are described by the Schroedinger and Pauli equations, describing the dynamics of particles of spin zero and 1/2 respectively, taking into account the structure of the transformations Galileo. Due to the operatorial, we represent Galileo's transformations by matrices by choosing an appropriate basis of space-time. Using these arrays, we saw group characteristics associated with these transformations, which we call the Galileo Group. We note the invariance of the Schroedinger and Pauli equations after these changes, as well as the physical state associated with it, which is represented by a radius vector in Hilbert space. (author)

  8. Relationship between quantum walks and relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Chandrashekar, C. M.; Banerjee, Subhashish; Srikanth, R.

    2010-01-01

    Quantum walk models have been used as an algorithmic tool for quantum computation and to describe various physical processes. This article revisits the relationship between relativistic quantum mechanics and the quantum walks. We show the similarities of the mathematical structure of the decoupled and coupled forms of the discrete-time quantum walk to that of the Klein-Gordon and Dirac equations, respectively. In the latter case, the coin emerges as an analog of the spinor degree of freedom. Discrete-time quantum walk as a coupled form of the continuous-time quantum walk is also shown by transforming the decoupled form of the discrete-time quantum walk to the Schroedinger form. By showing the coin to be a means to make the walk reversible and that the Dirac-like structure is a consequence of the coin use, our work suggests that the relativistic causal structure is a consequence of conservation of information. However, decoherence (modeled by projective measurements on position space) generates entropy that increases with time, making the walk irreversible and thereby producing an arrow of time. The Lieb-Robinson bound is used to highlight the causal structure of the quantum walk to put in perspective the relativistic structure of the quantum walk, the maximum speed of walk propagation, and earlier findings related to the finite spread of the walk probability distribution. We also present a two-dimensional quantum walk model on a two-state system to which the study can be extended.

  9. The interpretation of quantum mechanics: a case-study in the sociology of science

    International Nuclear Information System (INIS)

    Harvey, W.

    1981-01-01

    The aim of this study was to investigate the role of social processes in scientific investigation, and to relate the products of scientific activity to particular features of the social context in which that activity took place. The group of scientists under examination shared a common interest in the interpretation of Quantum Mechanics. This is not a typical scientific speciality; it lacks both a cohesive social structure and an agreed set of theories and practices. It is argued that social and cognitive factors interact in a complex way to bring about and maintain this fragmented state. In particular, methodological differences are identified as a major cause of disputes in this field. A sub-group of physicists performed experimental tests of Quantum Mechanics. Accounts of the behavior of these physicists in terms of general codes of scientific conduct (norms) seem to be unsatisfactory; instead, we must refer to many specific features of their local social context. The construction and evaluation of knowledge-claims can also be best described by referring to the cultural context of this work. These conclusions support a relativist view, in which the outcome of scientific activity is not uniquely determined by empirical data, but is flexible, and can reflect social pressures from inside or outside science. (author)

  10. Quantum mechanics a modern development

    CERN Document Server

    Ballentine, Leslie E

    2015-01-01

    Although there are many textbooks that deal with the formal apparatus of quantum mechanics (QM) and its application to standard problems, none take into account the developments in the foundations of the subject which have taken place in the last few decades. There are specialized treatises on various aspects of the foundations of QM, but none that integrate those topics with the standard material. This book aims to remove that unfortunate dichotomy, which has divorced the practical aspects of the subject from the interpretation and broader implications of the theory. In this edition a new chapter on quantum information is added. As the topic is still in a state of rapid development, a comprehensive treatment is not feasible. The emphasis is on the fundamental principles and some key applications, including quantum cryptography, teleportation of states, and quantum computing. The impact of quantum information theory on the foundations of quantum mechanics is discussed. In addition, there are minor revisions ...

  11. Mathematical foundation of quantum mechanics

    CERN Document Server

    Parthasarathy, K R

    2005-01-01

    This is a brief introduction to the mathematical foundations of quantum mechanics based on lectures given by the author to Ph.D.students at the Delhi Centre of the Indian Statistical Institute in order to initiate active research in the emerging field of quantum probability. The material in the first chapter is included in the author's book "An Introduction to Quantum Stochastic Calculus" published by Birkhauser Verlag in 1992 and the permission of the publishers to reprint it here is acknowledged. Apart from quantum probability, an understanding of the role of group representations in the development of quantum mechanics is always a fascinating theme for mathematicians. The first chapter deals with the definitions of states, observables and automorphisms of a quantum system through Gleason's theorem, Hahn-Hellinger theorem and Wigner's theorem. Mackey's imprimitivity theorem and the theorem of inducing representations of groups in stages are proved directly for projective unitary antiunitary representations ...

  12. Relativistic quantum mechanics of leptons and fields

    International Nuclear Information System (INIS)

    Grandy, W.T. Jr.

    1991-01-01

    This book serves as an advanced text on the Dirac theory, and provides a monograph summarizing the description of relativistic quantum mechanics and quantum electrodynamics as classical field theories. It presents a broad, detailed, and up-to-date exposition of relativistic quantum mechanics, including the two-body problem. It also demonstrates the extent to which the behavior of stable particles and their interactions can be understood without introducing operator (second-quantized) fields. The subsequent difficulties are studied in detail and possible resolutions are presented through quantum field theory

  13. A quantum information approach to statistical mechanics

    International Nuclear Information System (INIS)

    Cuevas, G.

    2011-01-01

    The field of quantum information and computation harnesses and exploits the properties of quantum mechanics to perform tasks more efficiently than their classical counterparts, or that may uniquely be possible in the quantum world. Its findings and techniques have been applied to a number of fields, such as the study of entanglement in strongly correlated systems, new simulation techniques for many-body physics or, generally, to quantum optics. This thesis aims at broadening the scope of quantum information theory by applying it to problems in statistical mechanics. We focus on classical spin models, which are toy models used in a variety of systems, ranging from magnetism, neural networks, to quantum gravity. We tackle these models using quantum information tools from three different angles. First, we show how the partition function of a class of widely different classical spin models (models in different dimensions, different types of many-body interactions, different symmetries, etc) can be mapped to the partition function of a single model. We prove this by first establishing a relation between partition functions and quantum states, and then transforming the corresponding quantum states to each other. Second, we give efficient quantum algorithms to estimate the partition function of various classical spin models, such as the Ising or the Potts model. The proof is based on a relation between partition functions and quantum circuits, which allows us to determine the quantum computational complexity of the partition function by studying the corresponding quantum circuit. Finally, we outline the possibility of applying quantum information concepts and tools to certain models of dis- crete quantum gravity. The latter provide a natural route to generalize our results, insofar as the central quantity has the form of a partition function, and as classical spin models are used as toy models of matter. (author)

  14. Coherent states in quantum mechanics

    International Nuclear Information System (INIS)

    Rodrigues, R. de Lima; Fernandes Junior, Damasio; Batista, Sheyla Marques

    2001-12-01

    We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out. (author)

  15. Coherent states in quantum mechanics

    CERN Document Server

    Rodrigues, R D L; Fernandes, D

    2001-01-01

    We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out.

  16. Communication: Quantum mechanics without wavefunctions

    Energy Technology Data Exchange (ETDEWEB)

    Schiff, Jeremy [Department of Mathematics, Bar-Ilan University, Ramat Gan 52900 (Israel); Poirier, Bill [Department of Chemistry and Biochemistry, Texas Tech University, Box 41061, Lubbock, Texas 79409-1061 (United States) and Department of Physics, Texas Tech University, Box 41051, Lubbock, Texas 79409-1051 (United States)

    2012-01-21

    We present a self-contained formulation of spin-free non-relativistic quantum mechanics that makes no use of wavefunctions or complex amplitudes of any kind. Quantum states are represented as ensembles of real-valued quantum trajectories, obtained by extremizing an action and satisfying energy conservation. The theory applies for arbitrary configuration spaces and system dimensionalities. Various beneficial ramifications--theoretical, computational, and interpretational--are discussed.

  17. Communication: Quantum mechanics without wavefunctions

    International Nuclear Information System (INIS)

    Schiff, Jeremy; Poirier, Bill

    2012-01-01

    We present a self-contained formulation of spin-free non-relativistic quantum mechanics that makes no use of wavefunctions or complex amplitudes of any kind. Quantum states are represented as ensembles of real-valued quantum trajectories, obtained by extremizing an action and satisfying energy conservation. The theory applies for arbitrary configuration spaces and system dimensionalities. Various beneficial ramifications--theoretical, computational, and interpretational--are discussed.

  18. Quantum mechanics and experience

    CERN Document Server

    Albert, David Z

    1992-01-01

    The more science tells us about the world, the stranger it looks. Ever since physics first penetrated the atom, early in this century, what it found there has stood as a radical and unanswered challenge to many of our most cherished conceptions of nature. It has literally been called into question since then whether or not there are always objective matters of fact about the whereabouts of subatomic particles, or about the locations of tables and chairs, or even about the very contents of our thoughts. A new kind of uncertainty has become a principle of science. This book is an original and provocative investigation of that challenge, as well as a novel attempt at writing about science in a style that is simultaneously elementary and deep. It is a lucid and self-contained introduction to the foundations of quantum mechanics, accessible to anyone with a high school mathematics education, and at the same time a rigorous discussion of the most important recent advances in our understanding of that subject, some...

  19. Entangled states in quantum mechanics

    Science.gov (United States)

    Ruža, Jānis

    2010-01-01

    In some circles of quantum physicists, a view is maintained that the nonseparability of quantum systems-i.e., the entanglement-is a characteristic feature of quantum mechanics. According to this view, the entanglement plays a crucial role in the solution of quantum measurement problem, the origin of the “classicality” from the quantum physics, the explanation of the EPR paradox by a nonlocal character of the quantum world. Besides, the entanglement is regarded as a cornerstone of such modern disciplines as quantum computation, quantum cryptography, quantum information, etc. At the same time, entangled states are well known and widely used in various physics areas. In particular, this notion is widely used in nuclear, atomic, molecular, solid state physics, in scattering and decay theories as well as in other disciplines, where one has to deal with many-body quantum systems. One of the methods, how to construct the basis states of a composite many-body quantum system, is the so-called genealogical decomposition method. Genealogical decomposition allows one to construct recurrently by particle number the basis states of a composite quantum system from the basis states of its forming subsystems. These coupled states have a structure typical for entangled states. If a composite system is stable, the internal structure of its forming basis states does not manifest itself in measurements. However, if a composite system is unstable and decays onto its forming subsystems, then the measurables are the quantum numbers, associated with these subsystems. In such a case, the entangled state has a dynamical origin, determined by the Hamiltonian of the corresponding decay process. Possible correlations between the quantum numbers of resulting subsystems are determined by the symmetries-conservation laws of corresponding dynamical variables, and not by the quantum entanglement feature.

  20. Quantum Mechanics as Classical Physics

    OpenAIRE

    Sebens, CT

    2015-01-01

    Here I explore a novel no-collapse interpretation of quantum mechanics which combines aspects of two familiar and well-developed alternatives, Bohmian mechanics and the many-worlds interpretation. Despite reproducing the empirical predictions of quantum mechanics, the theory looks surprisingly classical. All there is at the fundamental level are particles interacting via Newtonian forces. There is no wave function. However, there are many worlds.

  1. Quantum mechanics by walking 1. Foundations

    International Nuclear Information System (INIS)

    Pade, Jochen

    2012-01-01

    Quantum mechanics by walking introduces to the foundations of non-relativistic quantum mechanics. This book applies to studyings of teaching physics as well as all studyings of physics, who look for an appropriate, easy, fresh, and modern approach to the field. In the present first volume the essential principles of quantum mechanics are worked out. in order to be able to develop their mathematical formulation as fastly and clearly as possible, systematically between wave mechanics and algebraic presentation is changed. Beside themes, which are traditionally in textbooks of quantum mechanics, extensively actual aspects like interaction-free quantum measurement, neutrino oscillations, or quantum cryptography are considered as well as fundamental problems and epistemological questions discussed, as they occur in connection with the measurement process. The list of the postulates of quantum mechanics closes this volume; they form the framework for the extensions and applications, which are discussed in the second volume. The required mathematical aids are introduced step by step. In the appendix the most important mathematical tools are compactly collected, so that supplementing literature can be far reachingly abandoned. Furthermore in the appendix supplementing themes are deepened as for instance the Quantum Zeno effect or delayed-choice experiments.

  2. Applications of supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Rietdijk, R.H.

    1992-01-01

    The central subject of the thesis is the spinning particle model. It is a theory describing in a pseudoclassical way a Dirac particle which moves in an arbitrary d-dimensional space-time.In addition to space-time coordinates, the particle has spin which is described in terms of anti-commuting coordinates. Along the particles world line there is a super-symmetry between the fermionic spin variables and the bosonic position coordinates of the particle. It is straightforward to quantisize this model giving rise to supersymmetric quantum mechanics. The model does indeed describe a particle with spin 1/2, like a quark or an electron. There are two aspects of this model which is studied extensively in this thesis. First, to investigate the symmetries of the spinning particle on an arbitrary Riemannian manifold. Second, attention is drawn to the application of supersymmetric quantum mechanical models (i.e. spinning particle models) defined on an arbitrary Riemannian manifold to the calculation of anomalies in quantum field theories defined on the same manifold. (author). 49 refs.; 7 figs

  3. Contact geometry and quantum mechanics

    Science.gov (United States)

    Herczeg, Gabriel; Waldron, Andrew

    2018-06-01

    We present a generally covariant approach to quantum mechanics in which generalized positions, momenta and time variables are treated as coordinates on a fundamental "phase-spacetime". We show that this covariant starting point makes quantization into a purely geometric flatness condition. This makes quantum mechanics purely geometric, and possibly even topological. Our approach is especially useful for time-dependent problems and systems subject to ambiguities in choices of clock or observer. As a byproduct, we give a derivation and generalization of the Wigner functions of standard quantum mechanics.

  4. Quantum mechanics in Hilbert space

    CERN Document Server

    Prugovecki, Eduard

    1981-01-01

    A critical presentation of the basic mathematics of nonrelativistic quantum mechanics, this text is suitable for courses in functional analysis at the advanced undergraduate and graduate levels. Its readable and self-contained form is accessible even to students without an extensive mathematical background. Applications of basic theorems to quantum mechanics make it of particular interest to mathematicians working in functional analysis and related areas.This text features the rigorous proofs of all the main functional-analytic statements encountered in books on quantum mechanics. It fills the

  5. Variational principle in quantum mechanics

    International Nuclear Information System (INIS)

    Popiez, L.

    1986-01-01

    The variational principle in a standard, path integral formulation of quantum mechanics (as proposed by Dirac and Feynman) appears only in the context of a classical limit n to 0 and manifests itself through the method of abstract stationary phase. Symbolically it means that a probability amplitude averaged over trajectories denotes a classical evolution operator for points in a configuration space. There exists, however, the formulation of quantum dynamics in which variational priniple is one of basic postulates. It is explained that the translation between stochastic and quantum mechanics in this case can be understood as in Nelson's stochastic mechanics

  6. Density functional theory and quantum mechanics/molecular mechanics study of cysteine protease inhibition by nitrile-based inhibitors.

    Directory of Open Access Journals (Sweden)

    Sam P De Visser

    2013-12-01

    Full Text Available Cysteine protease enzymes are important for human physiology and catalyze key protein degradation pathways. These enzymes react via a nucleophilic reaction mechanism that involves a cysteine residue and the proton of a proximal histidine. Particularly efficient inhibitors of these enzymes are nitrile-based, however, the details of the catalytic reaction mechanism currently are poorly understood. To gain further insight into the inhibition of these molecules, we have performed a combined density functional theory and quantum mechanics/molecular mechanics study on the reaction of a nitrile-based inhibitor with the enzyme active site amino acids. We show here that small perturbations to the inhibitor structure can have dramatic effects on the catalysis and inhibition processes. Thus, we investigated a range of inhibitor templates and show that specific structural changes reduce the inhibitory efficiency by several orders of magnitude. Moreover, as the reaction takes place on a polar surface, we find strong differences between the DFT and QM/MM calculated energetics. In particular, the DFT model led to dramatic distortions from the starting structure and the convergence to a structure that would not fit the enzyme active site. In the subsequent QM/MM study we investigated the use of mechanical versus electronic embedding on the kinetics, thermodynamics and geometries along the reaction mechanism. We find minor effects on the kinetics of the reaction but large geometric and thermodynamics differences as a result of inclusion of electronic embedding corrections. The work here highlights the importance of model choice in the investigation of this biochemical reaction mechanism.

  7. New developments in quantum mechanics

    CERN Document Server

    Aharonov, Yakir

    1994-01-01

    After a general introduction, some new developments on the more subtle predictions of Quantum Mechanics and their interpretation will be discussed. These include non-local topological effects, physics of pre- and post-selected quantum systems, and the question of observability of the Schrödinger wave itself.

  8. Quantum mechanics from classical statistics

    International Nuclear Information System (INIS)

    Wetterich, C.

    2010-01-01

    Quantum mechanics can emerge from classical statistics. A typical quantum system describes an isolated subsystem of a classical statistical ensemble with infinitely many classical states. The state of this subsystem can be characterized by only a few probabilistic observables. Their expectation values define a density matrix if they obey a 'purity constraint'. Then all the usual laws of quantum mechanics follow, including Heisenberg's uncertainty relation, entanglement and a violation of Bell's inequalities. No concepts beyond classical statistics are needed for quantum physics - the differences are only apparent and result from the particularities of those classical statistical systems which admit a quantum mechanical description. Born's rule for quantum mechanical probabilities follows from the probability concept for a classical statistical ensemble. In particular, we show how the non-commuting properties of quantum operators are associated to the use of conditional probabilities within the classical system, and how a unitary time evolution reflects the isolation of the subsystem. As an illustration, we discuss a classical statistical implementation of a quantum computer.

  9. Fun with supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Freedman, B.; Cooper, F.

    1984-04-01

    One reason for studying supersymmetric quantum mechanics is that there are a class of superpotentials W(x) which behave at large x as x/sup α/ for which we know from general arguments whether SUSY is broken or unbroken. Thus one can use these superpotentials to test various ideas about how to see if supersymmetry is broken in an arbitrary model. Recently, Witten proposed a topological invariant, the Witten index Δ which counts the number of bosons minus the number of fermions having ground state energy zero. Since if supersymmetry is broken, the ground state energy cannot be zero, one expects if Δ is not zero, SUSY is preserved and the theory is not a good candidate for a realistic model. In this study we evaluate Δ for several examples, and show some unexpected peculiarities of the Witten index for certain choice of superpotentials W(x). We also discuss two other nonperturbative methods of studying supersymmetry breakdown. One involves relating supersymmetric quantum mechanics to a stochastic classical problem and the other involves considering a discrete (but not supersymmetric) version of the theory and studying its behavior as one removes the lattice cuttoff. In this survey we review the Hamiltonian and path integral approaches to supersymmetric quantum mechanics. We then discuss the related path integrals for the Witten Index and for stochastic processes and show how they are indications for supersymmetry breakdown. We then discuss a system where the superpotential W(x) has assymetrical values at +-infinity. We finally discuss nonperturbative strategies for studying supersymmetry breakdown based on introducing a lattice and studying the behavior of the ground state energy as the lattice cutoff is removed. 17 references

  10. Stochastic mechanics and quantum theory

    International Nuclear Information System (INIS)

    Goldstein, S.

    1987-01-01

    Stochastic mechanics may be regarded as both generalizing classical mechanics to processes with intrinsic randomness, as well as providing the sort of detailed description of microscopic events declared impossible under the traditional interpretation of quantum mechanics. It avoids the many conceptual difficulties which arise from the assumption that quantum mechanics, i.e., the wave function, provides a complete description of (microscopic) physical reality. Stochastic mechanics presents a unified treatment of the microscopic and macroscopic domains, in which the process of measurement plays no special physical role and which reduces to Newtonian mechanics in the macroscopic limit

  11. Quantum mechanics of history: The decoherence functional in quantum mechanics

    International Nuclear Information System (INIS)

    Dowker, H.F.; Halliwell, J.J.

    1992-01-01

    We study a formulation of quantum mechanics in which the central notion is that of a quantum-mechanical history---a sequence of events at a succession of times. The primary aim is to identify sets of ''decoherent'' (or ''consistent'') histories for the system. These are quantum-mechanical histories suffering negligible interference with each other, and, therefore, to which probabilities may be assigned. These histories may be found for a given system using the so-called decoherence functional. When the decoherence functional is exactly diagonal, probabilities may be assigned to the histories, and all probability sum rules are satisfied exactly. We propose a condition for approximate decoherence, and argue that it implies that most probability sum rules will be satisfied to approximately the same degree. We also derive an inequality bounding the size of the off-diagonal terms of the decoherence functional. We calculate the decoherence functional for some simple one-dimensional systems, with a variety of initial states. For these systems, we explore the extent to which decoherence is produced using two different types of coarse graining. The first type of coarse graining involves imprecise specification of the particle's position. The second involves coupling the particle to a thermal bath of harmonic oscillators and ignoring the details of the bath (the Caldeira-Leggett model). We argue that both types of coarse graining are necessary in general. We explicitly exhibit the degree of decoherence as a function of the temperature of the bath, and of the width to within which the particle's position is specified. We study the diagonal elements of the decoherence functional, representing the probabilities for the possible histories of the system

  12. Stochastic quantum mechanics and quantum spacetime

    International Nuclear Information System (INIS)

    Prugovecki, E.

    1984-01-01

    This monograph deals in part with the physical, mathematical and epistemological reasons behind the failure of past theoretical frameworks, including conventional relativistic quantum mechanics, to bring about a conssistent unification of relativity with quantum theory. The assessment of the past record is set in an historical perspective by citing from original sources, some of which might be partly forgotten or are not that well known, but forcefully illustrate the motivations and goals of the foudners of relativity and quantum theory as they set about developing their respetive disciplines. The proposed framework for unification, which constitutes the bulk of this book, embraces classical as well as quantum theories by implementing an epsitemic idea first put forth by M. Born, namely that all deterministic values for measurable quantitites. The framework gives rise to a whole range of yet unresearched problems, whose solutions are bound to shed some light on the relationship between relativity and quantum theories of the most fundamental physical and mathematical leves. (author). refs.; figs.; tabs

  13. Stochastic methods in quantum mechanics

    CERN Document Server

    Gudder, Stanley P

    2005-01-01

    Practical developments in such fields as optical coherence, communication engineering, and laser technology have developed from the applications of stochastic methods. This introductory survey offers a broad view of some of the most useful stochastic methods and techniques in quantum physics, functional analysis, probability theory, communications, and electrical engineering. Starting with a history of quantum mechanics, it examines both the quantum logic approach and the operational approach, with explorations of random fields and quantum field theory.The text assumes a basic knowledge of fun

  14. Quantum mechanical irreversibility and measurement

    CERN Document Server

    Grigolini, P

    1993-01-01

    This book is intended as a tutorial approach to some of the techniques used to deal with quantum dissipation and irreversibility, with special focus on their applications to the theory of measurements. The main purpose is to provide readers without a deep expertise in quantum statistical mechanics with the basic tools to develop a critical judgement on whether the major achievements in this field have to be considered a satisfactory solution of quantum paradox, or rather this ambitious achievement has to be postponed to when a new physics, more general than quantum and classical physics, will

  15. Quantum-mechanical study of ionization in slow collisions of antiprotons with hydrogen atoms

    International Nuclear Information System (INIS)

    Sakimoto, Kazuhiro

    2004-01-01

    The cross sections for the ionization p+H→p+p+e at low collision energies are computed with a complete quantum-mechanical method of time-dependent wave-packet propagation, which was applied to the protonium formation (→pp+e) by the present author [Phys. Rev. A 65, 012706 (2002)]. The ionization process shows very large cross sections even near threshold energy. An impact-parameter semiclassical method, in which the trajectory bending is taken into account by the introduction of the adiabatic potential, is also examined for the calculation of the ionization cross section. The semiclassical results are in good agreement with the quantum-mechanical results

  16. Relativistic quantum mechanics

    CERN Document Server

    Horwitz, Lawrence P

    2015-01-01

    This book describes a relativistic quantum theory developed by the author starting from the E.C.G. Stueckelberg approach proposed in the early 40s. In this framework a universal invariant evolution parameter (corresponding to the time originally postulated by Newton) is introduced to describe dynamical evolution. This theory is able to provide solutions for some of the fundamental problems encountered in early attempts to construct a relativistic quantum theory. A relativistically covariant construction is given for which particle spins and angular momenta can be combined through the usual rotation group Clebsch-Gordan coefficients. Solutions are defined for both the classical and quantum two body bound state and scattering problems. The recently developed quantum Lax-Phillips theory of semigroup evolution of resonant states is described. The experiment of Lindner and coworkers on interference in time is discussed showing how the property of coherence in time provides a simple understanding of the results. Th...

  17. A study on pre-service physics teachers' conceptualization on elementary quantum mechanics

    Directory of Open Access Journals (Sweden)

    Glauco Cohen Ferreira Pantoja

    2017-08-01

    Full Text Available In this work, we present the results of a research in which we aimed to evidence obstacles and advances in pre-service teachers’ conceptualization on a subject involving elementary Quantum Mechanics. We based our analysis on the theories due to David Ausubel and Gèrard Vergnaud to study Meaningful Learning patterns, both in predicative and operatory form of knowledge, of six students involved in a didactical intervention composed of six classes, in which we emphasized both similarities and differences between Classical and Quantum Physics. With this intervention, we intended to teach the concepts of Physical System, Dynamical Variables, State of a Physical System and Time Evolution. We guided our data analysis by the methodology of content analysis (Bardin, 2008 and it turned possible to map Meaningful Learning patterns involving the four concepts to which were associated a set of essential features (in the predicative stage and a set of theorems-in-action (in the operatory stage relating the aim-concepts in problem-solving or conceptual mapping.

  18. Geometry-based approach to studying the semi-classical limit in quantum dynamics by the coherent states and quantum mechanics on the torus

    International Nuclear Information System (INIS)

    Faure, F.

    1993-01-01

    This thesis deals with problems linked to the study of the semi-classical limit in quantum dynamics. The first part presents a geometrical formulation which is tantamount to the time dependent variational principle. The classical dynamics is considered as an orthogonal projection of the quantum dynamics on the family of coherent states. The angle of projection provides an information on the validity of the approximation. This angle is studied in an illustrating example. In the second part, we study quantum mechanics on the torus as a phase space, and particularly degeneracies in the spectrum of Harper like models or kicked Harper like models which manifest chaotic dynamics. These models find direct applications in solid state physics, especially with the quantum Hall effect. In this study, we use the Chern index, which is a topological characterization of the localization of the eigenfunctions as some periodicity conditions are changed. The use of the Husimi distribution provides a phase space representation of the quantum states. We discuss the role played by separatrix-states, by the effects of quantum tunneling, and by a classically chaotic dynamics. (orig.)

  19. Quantum mechanics I the fundamentals

    CERN Document Server

    Rajasekar, S

    2015-01-01

    Quantum Mechanics I: The Fundamentals provides a graduate-level account of the behavior of matter and energy at the molecular, atomic, nuclear, and sub-nuclear levels. It covers basic concepts, mathematical formalism, and applications to physically important systems.

  20. Stochastic incompleteness of quantum mechanics

    International Nuclear Information System (INIS)

    Suppes, P.; Zanotti, M.

    1976-01-01

    This article brings out in as conceptually clear terms as possible what seems to be a major incompleteness in the probability theory of particles offered by classical quantum mechanics. The exact nature of this incompleteness is illustrated by consideration of some simple quantum-mechanical examples. In addition, these examples are contrasted with the fundamental assumptions of Brownian motion in classical physics on the one hand, and with a controversey of a deecade ago in mathematical physchology. The central claim is that clasical quantum mechanics is radically incomplete in its probabilistic account of the motion of particles. In the last part of the article the time-dependent joint distribution of position and momentum of the linear harmonic oscillator is derived, and it is shown how the apparently physically paradoxical statistical independence of position and momentum has a natural explanation. The explanation is given within the framework of the non-quantum-mechanical stochastic theory constructed for such oscillators. (Auth.)

  1. Singular potentials in quantum mechanics

    International Nuclear Information System (INIS)

    Aguilera-Navarro, V.C.; Koo, E. Ley

    1995-10-01

    This paper is a review of some mathematical methods as recently developed and applied to deal with singular potentials in Quantum Mechanics. Regular and singular perturbative methods as well as variational treatments are considered. (author). 25 refs

  2. Computing With Quantum Mechanical Oscillators

    National Research Council Canada - National Science Library

    Parks, A

    1991-01-01

    Despite the obvious practical considerations (e.g., stability, controllability), certain quantum mechanical systems seem to naturally lend themselves in a theoretical sense to the task of performing computations...

  3. Quantum mechanics principles and formalism

    CERN Document Server

    McWeeny, Roy

    2012-01-01

    Focusing on main principles of quantum mechanics and their immediate consequences, this graduate student-oriented volume develops the subject as a fundamental discipline, opening with review of origins of Schrödinger's equations and vector spaces.

  4. How to understand quantum mechanics

    CERN Document Server

    Ralston, John P

    2018-01-01

    How to Understand Quantum Mechanics presents an accessible introduction to understanding quantum mechanics in a natural and intuitive way, which was advocated by Erwin Schroedinger and Albert Einstein. A theoretical physicist reveals dozens of easy tricks that avoid long calculations, makes complicated things simple, and bypasses the worthless anguish of famous scientists who died in angst. The author's approach is light-hearted, and the book is written to be read without equations, however all relevant equations still appear with explanations as to what they mean. The book entertainingly rejects quantum disinformation, the MKS unit system (obsolete), pompous non-explanations, pompous people, the hoax of the 'uncertainty principle' (it is just a math relation), and the accumulated junk-DNA that got into the quantum operating system by misreporting it. The order of presentation is new and also unique by warning about traps to be avoided, while separating topics such as quantum probability to let the Schroeding...

  5. Investigation of the CH3Cl + CN(-) reaction in water: Multilevel quantum mechanics/molecular mechanics study.

    Science.gov (United States)

    Xu, Yulong; Zhang, Jingxue; Wang, Dunyou

    2015-06-28

    The CH3Cl + CN(-) reaction in water was studied using a multilevel quantum mechanics/molecular mechanics (MM) method with the multilevels, electrostatic potential, density functional theory (DFT) and coupled-cluster single double triple (CCSD(T)), for the solute region. The detailed, back-side attack SN2 reaction mechanism was mapped along the reaction pathway. The potentials of mean force were calculated under both the DFT and CCSD(T) levels for the reaction region. The CCSD(T)/MM level of theory presents a free energy activation barrier height at 20.3 kcal/mol, which agrees very well with the experiment value at 21.6 kcal/mol. The results show that the aqueous solution has a dominant role in shaping the potential of mean force. The solvation effect and the polarization effect together increase the activation barrier height by ∼11.4 kcal/mol: the solvation effect plays a major role by providing about 75% of the contribution, while polarization effect only contributes 25% to the activation barrier height. Our calculated potential of mean force under the CCSD(T)/MM also has a good agreement with the one estimated using data from previous gas-phase studies.

  6. A quantum mechanical study of La-doped Pb(Zr,Ti)O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Stashans, Arvids [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)]. E-mail: arvids@utpl.edu.ec; Maldonado, Frank [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

    2007-04-15

    Lanthanum-modified Pb(Zr,Ti)O{sub 3} (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr{sub 0.53}Ti{sub 0.47}O{sub 3}, of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report.

  7. A quantum mechanical study of La-doped Pb(Zr,Ti)O3

    International Nuclear Information System (INIS)

    Stashans, Arvids; Maldonado, Frank

    2007-01-01

    Lanthanum-modified Pb(Zr,Ti)O 3 (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr 0.53 Ti 0.47 O 3 , of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report

  8. Observations on finite quantum mechanics

    International Nuclear Information System (INIS)

    Balian, R.; Itzykson, C.

    1986-01-01

    We study the canonical transformations of the quantum mechanics on a finite phase space. For simplicity we assume that the configuration variable takes an odd prime number 4 K±1 of distinct values. We show that the canonical group is unitarily implemented. It admits a maximal abelian subgroup of order 4 K, commuting with the finite Fourier transform F, a finite analogue of the harmonic oscillator group. This provides a natural construction of F 1/K and of an orthogonal basis of eigenstates of F [fr

  9. Quantum mechanics in phase space

    DEFF Research Database (Denmark)

    Hansen, Frank

    1984-01-01

    A reformulation of quantum mechanics for a finite system is given using twisted multiplication of functions on phase space and Tomita's theory of generalized Hilbert algebras. Quantization of a classical observable h is achieved when the twisted exponential Exp0(-h) is defined as a tempered....... Generalized Weyl-Wigner maps related to the notion of Hamiltonian weight are studied and used in the formulation of a twisted spectral theory for functions on phase space. Some inequalities for Wigner functions on phase space are proven. A brief discussion of the classical limit obtained through dilations...

  10. The physics of quantum mechanics

    CERN Document Server

    Binney, James

    2014-01-01

    The Physics of Quantum Mechanics aims to give students a good understanding of how quantum mechanics describes the material world. It shows that the theory follows naturally from the use of probability amplitudes to derive probabilities. It stresses that stationary states are unphysical mathematical abstractions that enable us to solve the theory's governing equation, the time-dependent Schroedinger equation. Every opportunity is taken to illustrate the emergence of the familiarclassical, dynamical world through the quantum interference of stationary states. The text stresses the continuity be

  11. Quantifying Quantum-Mechanical Processes.

    Science.gov (United States)

    Hsieh, Jen-Hsiang; Chen, Shih-Hsuan; Li, Che-Ming

    2017-10-19

    The act of describing how a physical process changes a system is the basis for understanding observed phenomena. For quantum-mechanical processes in particular, the affect of processes on quantum states profoundly advances our knowledge of the natural world, from understanding counter-intuitive concepts to the development of wholly quantum-mechanical technology. Here, we show that quantum-mechanical processes can be quantified using a generic classical-process model through which any classical strategies of mimicry can be ruled out. We demonstrate the success of this formalism using fundamental processes postulated in quantum mechanics, the dynamics of open quantum systems, quantum-information processing, the fusion of entangled photon pairs, and the energy transfer in a photosynthetic pigment-protein complex. Since our framework does not depend on any specifics of the states being processed, it reveals a new class of correlations in the hierarchy between entanglement and Einstein-Podolsky-Rosen steering and paves the way for the elaboration of a generic method for quantifying physical processes.

  12. Science Academies' Refresher Course in Quantum Mechanics

    Indian Academy of Sciences (India)

    IAS Admin

    2013-02-28

    Feb 28, 2013 ... A Refresher Course in Quantum Mechanics for college/university teachers ... The Course will cover the basic and advanced topics of Quantum ... Module 1:- Principles of Quantum Mechanics (with associated mathematics), ...

  13. Quantum ballistic evolution in quantum mechanics: Application to quantum computers

    International Nuclear Information System (INIS)

    Benioff, P.

    1996-01-01

    Quantum computers are important examples of processes whose evolution can be described in terms of iterations of single-step operators or their adjoints. Based on this, Hamiltonian evolution of processes with associated step operators T is investigated here. The main limitation of this paper is to processes which evolve quantum ballistically, i.e., motion restricted to a collection of nonintersecting or distinct paths on an arbitrary basis. The main goal of this paper is proof of a theorem which gives necessary and sufficient conditions that T must satisfy so that there exists a Hamiltonian description of quantum ballistic evolution for the process, namely, that T is a partial isometry and is orthogonality preserving and stable on some basis. Simple examples of quantum ballistic evolution for quantum Turing machines with one and with more than one type of elementary step are discussed. It is seen that for nondeterministic machines the basis set can be quite complex with much entanglement present. It is also proven that, given a step operator T for an arbitrary deterministic quantum Turing machine, it is decidable if T is stable and orthogonality preserving, and if quantum ballistic evolution is possible. The proof fails if T is a step operator for a nondeterministic machine. It is an open question if such a decision procedure exists for nondeterministic machines. This problem does not occur in classical mechanics. Also the definition of quantum Turing machines used here is compared with that used by other authors. copyright 1996 The American Physical Society

  14. Case Study of a Successful Learner's Epistemological Framings of Quantum Mechanics

    Science.gov (United States)

    Dini, Vesal; Hammer, David

    2017-01-01

    Research on student epistemologies in introductory courses has highlighted the importance of understanding physics as "a refinement of everyday thinking" [A. Einstein, J. Franklin Inst. 221, 349 (1936)]. That view is difficult to sustain in quantum mechanics, for students as for physicists. How might students manage the transition? In…

  15. Quantum Mechanics predicts evolutionary biology.

    Science.gov (United States)

    Torday, J S

    2018-07-01

    Nowhere are the shortcomings of conventional descriptive biology more evident than in the literature on Quantum Biology. In the on-going effort to apply Quantum Mechanics to evolutionary biology, merging Quantum Mechanics with the fundamentals of evolution as the First Principles of Physiology-namely negentropy, chemiosmosis and homeostasis-offers an authentic opportunity to understand how and why physics constitutes the basic principles of biology. Negentropy and chemiosmosis confer determinism on the unicell, whereas homeostasis constitutes Free Will because it offers a probabilistic range of physiologic set points. Similarly, on this basis several principles of Quantum Mechanics also apply directly to biology. The Pauli Exclusion Principle is both deterministic and probabilistic, whereas non-localization and the Heisenberg Uncertainty Principle are both probabilistic, providing the long-sought after ontologic and causal continuum from physics to biology and evolution as the holistic integration recognized as consciousness for the first time. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Measurement theory in quantum mechanics

    International Nuclear Information System (INIS)

    Klein, G.

    1980-01-01

    It is assumed that consciousness, memory and liberty (within the limits of the quantum mechanics indeterminism) are fundamental properties of elementary particles. Then, using this assumption it is shown how measurements and observers may be introduced in a natural way in the quantum mechanics theory. There are no longer fundamental differences between macroscopic and microscopic objects, between classical and quantum objects, between observer and object. Thus, discrepancies and paradoxes have disappeared from the conventional quantum mechanics theory. One consequence of the cumulative memory of the particles is that the sum of negentropy plus information is a constant. Using this theory it is also possible to explain the 'paranormal' phenomena and what is their difference from the 'normal' ones [fr

  17. Quantum mechanics in a nutshell

    CERN Document Server

    Mahan, Gerald D

    2009-01-01

    Covering the fundamentals as well as many special topics of current interest, this is the most concise, up-to-date, and accessible graduate-level textbook on quantum mechanics available. Written by Gerald Mahan, a distinguished research physicist and author of an acclaimed textbook on many-particle physics, Quantum Mechanics in a Nutshell is the distillation of many years' teaching experience. Emphasizing the use of quantum mechanics to describe actual quantum systems such as atoms and solids, and rich with interesting applications, the book proceeds from solving for the properties of a single particle in potential; to solving for two particles (the helium atom); to addressing many-particle systems. Applications include electron gas, magnetism, and Bose-Einstein Condensation; examples are carefully chosen and worked; and each chapter has numerous homework problems, many of them original

  18. Emergent quantum mechanics without wavefunctions

    Science.gov (United States)

    Mesa Pascasio, J.; Fussy, S.; Schwabl, H.; Grössing, G.

    2016-03-01

    We present our model of an Emergent Quantum Mechanics which can be characterized by “realism without pre-determination”. This is illustrated by our analytic description and corresponding computer simulations of Bohmian-like “surreal” trajectories, which are obtained classically, i.e. without the use of any quantum mechanical tool such as wavefunctions. However, these trajectories do not necessarily represent ontological paths of particles but rather mappings of the probability density flux in a hydrodynamical sense. Modelling emergent quantum mechanics in a high-low intesity double slit scenario gives rise to the “quantum sweeper effect” with a characteristic intensity pattern. This phenomenon should be experimentally testable via weak measurement techniques.

  19. Emergent quantum mechanics without wavefunctions

    International Nuclear Information System (INIS)

    Pascasio, J Mesa; Fussy, S; Schwabl, H; Grössing, G

    2016-01-01

    We present our model of an Emergent Quantum Mechanics which can be characterized by “realism without pre-determination”. This is illustrated by our analytic description and corresponding computer simulations of Bohmian-like “surreal” trajectories, which are obtained classically, i.e. without the use of any quantum mechanical tool such as wavefunctions. However, these trajectories do not necessarily represent ontological paths of particles but rather mappings of the probability density flux in a hydrodynamical sense. Modelling emergent quantum mechanics in a high-low intesity double slit scenario gives rise to the “quantum sweeper effect” with a characteristic intensity pattern. This phenomenon should be experimentally testable via weak measurement techniques. (paper)

  20. Study of quantum hadronic states using new optimum principles and new coherent production mechanisms

    International Nuclear Information System (INIS)

    Ion, D. B.; Ion, M. L.; Ion-Mihai, R.

    2002-01-01

    We introduced a new kind of quantum entropy for quantum scattering: conjugated nonextensivity entropy S Jθ bar (p,q). Using this new kind of nonextensive entropy we studied the nonextensive quantum scattering states of the hadronic interactions. We proved that probability distributions produced at quantum equilibrium coincide with optimal distributions given by the principle of minimum distance in the space of quantum scattering states. Using optimal states we proved new uncertainty relations and new entropic bands: For experimental tests we used the available phase shifts for the pion-nucleus scatterings and also for the pion-nucleon scatterings. Experimental tests of entropic bands and principle of maximum entropy for conjugated nonextensivity entropy are compared with entropic bands for usual entropy of joint probability S Jθ bar (p) and for pion-nucleus scatterings. Also given are the experimental tests of entropic bands and principle of maximum entropy for conjugated nonextensivity entropy compared with entropic bands for usual entropy of joint probability S Jθ bar (p) and for pion-nucleon scatterings.Our experimental tests proved the existence of the principle of limited entropic uncertainty in hadronic scattering. The experimental tests showed clearly that quantum elastic scattering is well described by the principle of minimum distance in the space of quantum states. By these results we obtained strong evidence for the nonextensivity of the hadronic scattering statistics. (authors)

  1. On obtaining classical mechanics from quantum mechanics

    International Nuclear Information System (INIS)

    Date, Ghanashyam

    2007-01-01

    Constructing a classical mechanical system associated with a given quantum-mechanical one entails construction of a classical phase space and a corresponding Hamiltonian function from the available quantum structures and a notion of coarser observations. The Hilbert space of any quantum-mechanical system naturally has the structure of an infinite-dimensional symplectic manifold ('quantum phase space'). There is also a systematic, quotienting procedure which imparts a bundle structure to the quantum phase space and extracts a classical phase space as the base space. This works straightforwardly when the Hilbert space carries weakly continuous representation of the Heisenberg group and one recovers the linear classical phase space R 2N . We report on how the procedure also allows extraction of nonlinear classical phase spaces and illustrate it for Hilbert spaces being finite dimensional (spin-j systems), infinite dimensional but separable (particle on a circle) and infinite dimensional but non-separable (polymer quantization). To construct a corresponding classical dynamics, one needs to choose a suitable section and identify an effective Hamiltonian. The effective dynamics mirrors the quantum dynamics provided the section satisfies conditions of semiclassicality and tangentiality

  2. Ortho-para H₂ conversion by proton exchange at low temperature: an accurate quantum mechanical study.

    Science.gov (United States)

    Honvault, P; Jorfi, M; González-Lezana, T; Faure, A; Pagani, L

    2011-07-08

    We report extensive, accurate fully quantum, time-independent calculations of cross sections at low collision energies, and rate coefficients at low temperatures for the H⁺ + H₂(v = 0, j) → H⁺ + H₂(v = 0, j') reaction. Different transitions are considered, especially the ortho-para conversion (j = 1 → j' = 0) which is of key importance in astrophysics. This conversion process appears to be very efficient and dominant at low temperature, with a rate coefficient of 4.15 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ at 10 K. The quantum mechanical results are also compared with statistical quantum predictions and the reaction is found to be statistical in the low temperature regime (T < 100 K).

  3. Superconducting Qubits as Mechanical Quantum Engines.

    Science.gov (United States)

    Sachtleben, Kewin; Mazon, Kahio T; Rego, Luis G C

    2017-09-01

    We propose the equivalence of superconducting qubits with a pistonlike mechanical quantum engine. The work reports a study on the nature of the nonequilibrium work exchanged with the quantum-nonadiabatic working medium, which is modeled as a multilevel coupled quantum well system subject to an external control parameter. The quantum dynamics is solved for arbitrary control protocols. It is shown that the work output has two components: one that depends instantaneously on the level populations and another that is due to the quantum coherences built in the system. The nonadiabatic coherent dynamics of the quantum engine gives rise to a resistance (friction) force that decreases the work output. We consider the functional equivalence of such a device and a rf-SQUID flux qubit.

  4. A mathematical companion to quantum mechanics

    CERN Document Server

    Sternberg, Shlomo

    2019-01-01

    This original 2018 work, based on the author's many years of teaching at Harvard University, examines mathematical methods of value and importance to advanced undergraduates and graduate students studying quantum mechanics. Topics include the Fourier transform, the spectral theorem for bounded self-joint operators, unbounded operators and semigroups, Weyl's theorem, the Rayleigh-Ritz method, one dimensional quantum mechanics, Ruelle's theorem, scattering theory, and many other subjects.

  5. Relativistic quantum mechanics an introduction to relativistic quantum fields

    CERN Document Server

    Maiani, Luciano

    2016-01-01

    Written by two of the world's leading experts on particle physics and the standard model - including an award-winning former Director General of CERN - this textbook provides a completely up-to-date account of relativistic quantum mechanics and quantum field theory. It describes the formal and phenomenological aspects of the standard model of particle physics, and is suitable for advanced undergraduate and graduate students studying both theoretical and experimental physics.

  6. Quantum mechanics and precision measurements

    International Nuclear Information System (INIS)

    Ramsey, N.F.

    1995-01-01

    The accuracies of measurements of almost all fundamental physical constants have increased by factors of about 10000 during the past 60 years. Although some of the improvements are due to greater care, most are due to new techniques based on quantum mechanics. Although the Heisenberg Uncertainty Principle often limits measurement accuracies, in many cases the validity of quantum mechanics makes possible the vastly improved measurement accuracies. Seven quantum features that have a profound influence on the science of measurements are: 1) Existence of discrete quantum states of energy. 2) Energy conservation in transitions between two states. 3) Electromagnetic radiation of frequency v is quantized with energy hv per quantum. 4) The identity principle. 5) The Heisenberg Uncertainty Principle. 6) Addition of probability amplitudes (not probabilities). 7) Wave and coherent phase phenomena. Of these seven quantum features, only the Heisenberg Uncertainty Principle limits the accuracy of measurements, and its effect is often negligibly small. The other six features make possible much more accurate measurements of quantum systems than with almost all classical systems. These effects are discussed and illustrated

  7. Quantum mechanics in matrix form

    CERN Document Server

    Ludyk, Günter

    2018-01-01

    This book gives an introduction to quantum mechanics with the matrix method. Heisenberg's matrix mechanics is described in detail. The fundamental equations are derived by algebraic methods using matrix calculus. Only a brief description of Schrödinger's wave mechanics is given (in most books exclusively treated), to show their equivalence to Heisenberg's matrix  method. In the first part the historical development of Quantum theory by Planck, Bohr and Sommerfeld is sketched, followed by the ideas and methods of Heisenberg, Born and Jordan. Then Pauli's spin and exclusion principles are treated. Pauli's exclusion principle leads to the structure of atoms. Finally, Dirac´s relativistic quantum mechanics is shortly presented. Matrices and matrix equations are today easy to handle when implementing numerical algorithms using standard software as MAPLE and Mathematica.

  8. Quantum mechanics interpretation: scalled debate

    International Nuclear Information System (INIS)

    Sanchez Gomez, J. L.

    2000-01-01

    This paper discusses the two main issues of the so called quantum debate, that started in 1927 with the famous Bohr-Einstein controversy; namely non-separability and the projection postulate. Relevant interpretations and formulations of quantum mechanics are critically analyzed in the light of the said issues. The treatment is focused chiefly on fundamental points, so that technical ones are practically not dealt with here. (Author) 20 refs

  9. Learn Quantum Mechanics with Haskell

    Directory of Open Access Journals (Sweden)

    Scott N. Walck

    2016-11-01

    Full Text Available To learn quantum mechanics, one must become adept in the use of various mathematical structures that make up the theory; one must also become familiar with some basic laboratory experiments that the theory is designed to explain. The laboratory ideas are naturally expressed in one language, and the theoretical ideas in another. We present a method for learning quantum mechanics that begins with a laboratory language for the description and simulation of simple but essential laboratory experiments, so that students can gain some intuition about the phenomena that a theory of quantum mechanics needs to explain. Then, in parallel with the introduction of the mathematical framework on which quantum mechanics is based, we introduce a calculational language for describing important mathematical objects and operations, allowing students to do calculations in quantum mechanics, including calculations that cannot be done by hand. Finally, we ask students to use the calculational language to implement a simplified version of the laboratory language, bringing together the theoretical and laboratory ideas.

  10. Nonlinear operators and nonlinear transformations studied via the differential form of the completeness relation in quantum mechanics

    International Nuclear Information System (INIS)

    Fan Hongyi; Yu Shenxi

    1994-01-01

    We show that the differential form of the fundamental completeness relation in quantum mechanics and the technique of differentiation within an ordered product (DWOP) of operators provide a new approach for calculating normal product expansions of some nonlinear operators and study some nonlinear transformations. Their usefulness in perturbative calculations is pointed out. (orig.)

  11. Classical and quantum mechanical studies of HF in an intense laser field

    International Nuclear Information System (INIS)

    Dardi, P.S.; Gray, S.K.

    1982-01-01

    The behavior of an HF molecule in an intense laser field is investigated with both classical trajectories and quantum dynamics. Vibration-rotation transition probabilities and energy absorption as a function of laser pulse time are calculated for the diatomic initially in its ground state. For comparison, results are also reported for a model nonrotating HF molecule. It is found that classical mechanics does not predict the correct time behavior of the system, nor does it predict the correct rotational state distributions. Classical mechanics does, however, predict pulse time averaged quantities to be the correct order of magnitude. There is also a correct general trend of increased multiphoton excitation for laser frequencies red-shifted from the one-photon resonance, although multiphoton resonance peaks are not observed in the classical results and far too little multiphoton excitation is predicted. The effect of laser phase has also been investigated and shown to be relatively unimportant in both the classical and quantum dynamics

  12. Quantum Mechanical Earth: Where Orbitals Become Orbits

    Science.gov (United States)

    Keeports, David

    2012-01-01

    Macroscopic objects, although quantum mechanical by nature, conform to Newtonian mechanics under normal observation. According to the quantum mechanical correspondence principle, quantum behavior is indistinguishable from classical behavior in the limit of very large quantum numbers. The purpose of this paper is to provide an example of the…

  13. Non-relativistic quantum mechanics

    CERN Document Server

    Puri, Ravinder R

    2017-01-01

    This book develops and simplifies the concept of quantum mechanics based on the postulates of quantum mechanics. The text discusses the technique of disentangling the exponential of a sum of operators, closed under the operation of commutation, as the product of exponentials to simplify calculations of harmonic oscillator and angular momentum. Based on its singularity structure, the Schrödinger equation for various continuous potentials is solved in terms of the hypergeometric or the confluent hypergeometric functions. The forms of the potentials for which the one-dimensional Schrödinger equation is exactly solvable are derived in detail. The problem of identifying the states of two-level systems which have no classical analogy is addressed by going beyond Bell-like inequalities and separability. The measures of quantumness of mutual information in two two-level systems is also covered in detail. Offers a new approach to learning quantum mechanics based on the history of quantum mechanics and its postu...

  14. Recent developments in quantum mechanics

    International Nuclear Information System (INIS)

    Piron, C.

    1989-01-01

    It is essentially a review of recent progress in Quantum Mechanics obtained by the ''Geneva School'', put all together in a synthesis for the first time. During these twelve last years Quantum Mechanics has developed deeply in three aspects: 1) the interpretation has been completely clarified but many ''senior'' physicists delight in the mystery of their school-days Quantum Mechanics and do not want to change their minds. 2) The formalism has been developed and generalized to many (if it is not all) physical situations. 3) Many new rules of calculation have been developed. In conclusion many paradoxes and/or unsolved problems have been solved and many calculations which usually appear just as tricks can be explained and justified. I want here to give a brief survey of each one of these three points and to end by some examples which show the power and the efficiency of this new theory. (orig.)

  15. Quantum-mechanical DFT calculation supported Raman spectroscopic study of some amino acids in bovine insulin.

    Science.gov (United States)

    Tah, Bidisha; Pal, Prabir; Roy, Sourav; Dutta, Debodyuti; Mishra, Sabyashachi; Ghosh, Manash; Talapatra, G B

    2014-08-14

    In this article Quantum mechanical (QM) calculations by Density Functional Theory (DFT) have been performed of all amino acids present in bovine insulin. Simulated Raman spectra of those amino acids are compared with their experimental spectra and the major bands are assigned. The results are in good agreement with experiment. We have also verified the DFT results with Quantum mechanical molecular mechanics (QM/MM) results for some amino acids. QM/MM results are very similar with the DFT results. Although the theoretical calculation of individual amino acids are feasible, but the calculated Raman spectrum of whole protein molecule is difficult or even quite impossible task, since it relies on lengthy and costly quantum-chemical computation. However, we have tried to simulate the Raman spectrum of whole protein by adding the proportionate contribution of the Raman spectra of each amino acid present in this protein. In DFT calculations, only the contributions of disulphide bonds between cysteines are included but the contribution of the peptide and hydrogen bonds have not been considered. We have recorded the Raman spectra of bovine insulin using micro-Raman set up. The experimental spectrum is found to be very similar with the resultant simulated Raman spectrum with some exceptions. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Study of optimum methods of optical communication. [accounting for the effects of the turbulent atmosphere and quantum mechanics

    Science.gov (United States)

    Harger, R. O.

    1974-01-01

    Abstracts are reported relating to the techniques used in the research concerning optical transmission of information. Communication through the turbulent atmosphere, quantum mechanics, and quantum communication theory are discussed along with the results.

  17. Stochastic theories of quantum mechanics

    International Nuclear Information System (INIS)

    De la Pena, L.; Cetto, A.M.

    1991-01-01

    The material of this article is organized into five sections. In Sect. I the basic characteristics of quantum systems are briefly discussed, with emphasis on their stochastic properties. In Sect. II a version of stochastic quantum mechanics is presented, to conclude that the quantum formalism admits an interpretation in terms of stochastic processes. In Sect. III the elements of stochastic electrodynamics are described, and its possibilities and limitations as a fundamental theory of quantum systems are discussed. Section IV contains a recent reformulation that overcomes the limitations of the theory discussed in the foregoing section. Finally, in Sect. V the theorems of EPR, Von Neumann and Bell are discussed briefly. The material is pedagogically presented and includes an ample list of references, but the details of the derivations are generally omitted. (Author)

  18. Effects of metal-ion replacement on pyrazinamidase activity: A quantum mechanical study.

    Science.gov (United States)

    Khadem-Maaref, Mahmoud; Mehrnejad, Faramarz; Phirouznia, Arash

    2017-05-01

    Pyrazinamidase (PZase), a metalloenzyme, is responsible for acidic modification of pyrazinamide (PZA), a drug used in tuberculosis treatment. The metal coordination site of the enzyme is able to coordinate various divalent metal cofactors. Previous experimental studies have demonstrated that metal ions, such as Co 2+ , Mn 2+ , and Zn 2+ , are able to reactivate metal-depleted PZase, while others including Cu 2+ , Fe 2+ , and Mg 2+ , cannot restore activity. In this study, we investigated binding of various metal ions to the metal coordination site (MCS) of the enzyme using quantum mechanical calculations. We calculated the metal-ligand (residue) binding energy and the atomic partial charges in the presence of various ions. The results indicated that the tendency of alkaline earth metals to bind to PZase MCS is very low and not suitable for enzyme structural and catalytic function. In contrast, Co 2+ and Ni 2+ ions have very high binding affinity and are favorable to the structural and functional properties of the enzyme. Furthermore, we observed that the rate at which Ni 2+ , Co 2+ and Fe 2+ ions in PZase MCS polarize the OH bond of coordinated water molecules is much higher than the polarization rate created by other ions. This finding suggests that the coordination of Ni 2+ , Co 2+ , or Fe 2+ to PZase facilitates the deprotonation of coordinated water molecules to generate a nucleophile that catalyzes the enzymatic reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Azobenzene as a photoregulator covalently attached to RNA: a quantum mechanics/molecular mechanics-surface hopping dynamics study.

    Science.gov (United States)

    Mondal, Padmabati; Granucci, Giovanni; Rastädter, Dominique; Persico, Maurizio; Burghardt, Irene

    2018-05-28

    The photoregulation of nucleic acids by azobenzene photoswitches has recently attracted considerable interest in the context of emerging biotechnological applications. To understand the mechanism of photoinduced isomerisation and conformational control in these complex biological environments, we employ a Quantum Mechanics/Molecular Mechanics (QM/MM) approach in conjunction with nonadiabatic Surface Hopping (SH) dynamics. Two representative RNA-azobenzene complexes are investigated, both of which contain the azobenzene chromophore covalently attached to an RNA double strand via a β-deoxyribose linker. Due to the pronounced constraints of the local RNA environment, it is found that trans -to- cis isomerization is slowed down to a time scale of ∼10-15 picoseconds, in contrast to 500 femtoseconds in vacuo , with a quantum yield reduced by a factor of two. By contrast, cis -to- trans isomerization remains in a sub-picosecond regime. A volume-conserving isomerization mechanism is found, similarly to the pedal-like mechanism previously identified for azobenzene in solution phase. Strikingly, the chiral RNA environment induces opposite right-handed and left-handed helicities of the ground-state cis -azobenzene chromophore in the two RNA-azobenzene complexes, along with an almost completely chirality conserving photochemical pathway for these helical enantiomers.

  20. The interpretation of quantum mechanics

    International Nuclear Information System (INIS)

    Pippard, A.B.

    1986-01-01

    It is argued that the reduction of the wavepacket following a measurement is no more than a computational convenience to which no meaning should be attached. In a strict application of quantum mechanics all measuring instruments must be included in a single wavefunction. Thus the activity of physics is treated as the analysis of public information, as conveyed by instruments, with quantum mechanics the accepted analytical procedure rather than a model of objective reality. Finally the classical world of particle trajectories that can be agreed on by all observers is shown to be a natural corollary. (author)

  1. General principles of quantum mechanics

    International Nuclear Information System (INIS)

    Pauli, W.

    1980-01-01

    This book is a textbook for a course in quantum mechanics. Starting from the complementarity and the uncertainty principle Schroedingers equation is introduced together with the operator calculus. Then stationary states are treated as eigenvalue problems. Furthermore matrix mechanics are briefly discussed. Thereafter the theory of measurements is considered. Then as approximation methods perturbation theory and the WKB approximation are introduced. Then identical particles, spin, and the exclusion principle are discussed. There after the semiclassical theory of radiation and the relativistic one-particle problem are discussed. Finally an introduction is given into quantum electrodynamics. (HSI)

  2. Quantum mechanics reality and separability

    International Nuclear Information System (INIS)

    Selleri, F.; Tarozzi, G.

    1981-01-01

    For many decades, there has been a debate about which one should be the correct interpretation of Quantum Mechanics. With regard to this question, the Copenhagen-Goettingen interpretation was in conflict with the interpretation given by Einstein and other physicists. The so-called problem of ''completeness'' of the theory in particular was under investigation. The development of this controversial problem, from the Von Neumann theorem up to the discovery of Bell inequality is reviewed in this article and it is discussed how these events marked the beginning of a new era for the researches on Quantum Mechanics. (author)

  3. Quantum Statistical Mechanics on a Quantum Computer

    NARCIS (Netherlands)

    Raedt, H. De; Hams, A.H.; Michielsen, K.; Miyashita, S.; Saito, K.; Saito, E.

    2000-01-01

    We describe a simulation method for a quantum spin model of a generic, general purpose quantum computer. The use of this quantum computer simulator is illustrated through several implementations of Grover’s database search algorithm. Some preliminary results on the stability of quantum algorithms

  4. BOOK REVIEWS: Quantum Mechanics: Fundamentals

    Science.gov (United States)

    Whitaker, A.

    2004-02-01

    Scientific edition of Bell’s collected works. Thus it is exceedingly interesting to discover how he has responded to Bell’s criticisms in the new edition of the book. To commence with general discussion of the new book, the authors recognise that the graduate student of today almost certainly has substantial experience of wave mechanics, and is probably familiar with the Dirac formalism. The 1966 edition had what seems, at least in retrospect, a relatively soft opening covering the basic ideas of wave mechanics and a substantial number of applications; it did not reach the Dirac formalism in the first two hundred pages, though it then moved on to tackle rather advanced topics, including a very substantial section on symmetries, which tackled a range of sophisticated issues. The new edition has been almost entirely rewritten; even at the level of basic text, it is difficult to trace sentences or paragraphs that have moved unscathed from one edition to the next. As well as the new topics, many of the old ones are discussed in much greater depth, and the general organisation is entirely different. As compared with the steady rise in level of the 1966 edition, the level of this book is fairly consistent throughout, and from the perspective of a beginning graduate student, I would estimate, a little tough. A brief introductory chapter gives a useful, though not particularly straightforward, discussion of complementarity, uncertainty and superposition, and concludes with an informative though very short summary of the discovery of quantum mechanics, together with a few nice photographs of some of its founders. There follow two substantial chapters which are preparation for the later study of actual systems. The first, called ‘The Formal Framework’ is a fairly comprehensive survey of the methods of quantum theory---Hilbert space, Dirac notation, mixtures, the density matrix, entanglement, canonical quantization, equations of motion, symmetries, conservation laws

  5. Holistic aspects of quantum mechanics

    International Nuclear Information System (INIS)

    Pietschmann, H.

    1987-01-01

    Aspects of quantum mechanics irreconcilable with classical physics are outlined. Quantum mechanics started with a negative statement about reality, namely: it is impossible to determine momentum and position of a particle simultaneously. Meanwhile it has generated an impressive body of predictions which can be tested and have been confirmed by suitable experiments. As a consequence a naive, local, materialistic concept of reality must be abolished and a novel approach, the holistic is introduced. This is illustrated by some examples e.g. the Pauli exclusion principle for electrons, the electron capture decay of 135 La as a model of the wavefunction reduction, the Bohr radius of the atom, electron localisation in the atom. An example from the quantum field theory is the calculation of magnetic moments of electron and muon where a particle cannot be considered separately and all other particles must be taken into account. (G.Q.)

  6. Numerical study of the time evolution of a wave packet in quantum mechanics

    International Nuclear Information System (INIS)

    Segura, J.; Fernandez de Cordoba, P.

    1993-01-01

    We solve the Schrodinger equation in order to study the time evolution of a wave packet in different situations of physical interest. This work illustrates, with pedagogical aim, some quantum phenomena which shock our classical conception of the universe: propagation in classically forbidden regions, energy quantization. (Author)

  7. Undergraduate quantum mechanics: lost opportunities for engaging motivated students?

    Science.gov (United States)

    Johansson, Anders

    2018-03-01

    Quantum mechanics is widely recognised as an important and difficult subject, and many studies have been published focusing on students’ conceptual difficulties. However, the sociocultural aspects of studying such an emblematic subject have not been researched to any large extent. This study explores students’ experiences of undergraduate quantum mechanics using qualitative analysis of semi-structured interview data. The results inform discussions about the teaching of quantum mechanics by adding a sociocultural dimension. Students pictured quantum mechanics as an intriguing subject that inspired them to study physics. The study environment they encountered when taking their first quantum mechanics course was however not always as inspiring as expected. Quantum mechanics instruction has commonly focused on the mathematical framework of quantum mechanics, and this kind of teaching was also what the interviewees had experienced. Two ways of handling the encounter with a traditional quantum mechanics course were identified in the interviews; either students accept the practice of studying quantum mechanics in a mathematical, exercise-centred way or they distance themselves from these practices and the subject. The students who responded by distancing themselves experienced a crisis and disappointment, where their experiences did not match the way they imagined themselves engaging with quantum mechanics. The implications of these findings are discussed in relation to efforts to reform the teaching of undergraduate quantum mechanics.

  8. Time in Quantum Mechanics

    International Nuclear Information System (INIS)

    Reznik, B.

    1999-01-01

    Time plays an unusual role in quantum theory, and the measurement of time is very different from the measurement of other physical qualities associated with a particle. As an example, the measurability of when something occurred is conceptually fraught with difficulties within the theory. Time must be measured by clocks, and one must somehow cause the occurrence of the event of interest to interact with a clock to record when that event occurred. But that interaction carries with it an inevitable perturbation of the event itself. I will argue that in addition to the usual ΔtΔE > ℎ associated with the accuracy of any clock, there is an additional ΔtE > ℎ uncertainty in the measurement of the time of arrival of a particle. Furthermore this constraint arises because the timing device can itself prevent the event from ever occurring at all. I will compare time measurements involving physical clocks, with attempts to construct a time operator and describe new difficulties associated with the latter approach

  9. Irreversibility in quantum mechanics

    International Nuclear Information System (INIS)

    Kadomtsev, Boris B

    2003-01-01

    From the Editorial Board. November 9, 2003 would have marked the seventy-fifth birthday of Boris Borisovich Kadomtsev, were he alive. An outstanding theoretical physicist, teacher, and enlightener, a prominent scientist in plasma physics and controlled nuclear fusion, Kadomtsev was also actively involved in science organization activities. In particular, from 1976 until his untimely death on August 19, 1998, Kadomtsev was the Editor-in-Chief of Physics-Uspekhi, and it is owing to his efforts that the journal improved notably during his tenure. Now, the Editorial Board, with gratitude and sorrow, would like to celebrate his birthday and to honor his blessed memory in these pages. There is, however, a rule - indeed an immutable tradition - in the journal that, except for the Personalia section, no anniversary can be marked in any way other than in a scientific publication. This rule was strictly observed under Kadomtsev, and certainly should not be violated now, even when honoring his memory. Fortunately, there is a video which remained of a lecture on modern problems of quantum physics that Kadomtsev delivered on May 12, 1997. Prepared for publication by M B Kadomtsev, the lecture allows the reader to revisit the heritage of B B Kadomtsev, to appreciate his logic in treating this very difficult area of physics, to hear his voice as it were, to recall Boris Borisovich Kadomtsev and to honor his memory. (methodological notes)

  10. Toy Models of a Nonassociative Quantum Mechanics

    International Nuclear Information System (INIS)

    Dzhunushaliev, V.

    2007-01-01

    Toy models of a nonassociative quantum mechanics are presented. The Heisenberg equation of motion is modified using a nonassociative commutator. Possible physical applications of a nonassociative quantum mechanics are considered. The idea is discussed that a nonassociative algebra could be the operator language for the nonperturbative quantum theory. In such approach the nonperturbative quantum theory has observables and un observables quantities.

  11. Axioms for nonrelativistic quantum mechanics

    International Nuclear Information System (INIS)

    Guz, W.

    1977-01-01

    On the basis of the axioms assumed it is proved that the logic of propositions concerning any quantum-mechanical system may be endowed with the structure of an orthomodular atomistic complete lattice satisfying the covering postulate, and hence, as a consequence of these axioms, the Piron-MacLaren representation theorem for the logic is obtained. (author)

  12. Renormalization group in quantum mechanics

    International Nuclear Information System (INIS)

    Polony, J.

    1996-01-01

    The running coupling constants are introduced in quantum mechanics and their evolution is described with the help of the renormalization group equation. The harmonic oscillator and the propagation on curved spaces are presented as examples. The Hamiltonian and the Lagrangian scaling relations are obtained. These evolution equations are used to construct low energy effective models. Copyright copyright 1996 Academic Press, Inc

  13. Probable Inference and Quantum Mechanics

    International Nuclear Information System (INIS)

    Grandy, W. T. Jr.

    2009-01-01

    In its current very successful interpretation the quantum theory is fundamentally statistical in nature. Although commonly viewed as a probability amplitude whose (complex) square is a probability, the wavefunction or state vector continues to defy consensus as to its exact meaning, primarily because it is not a physical observable. Rather than approach this problem directly, it is suggested that it is first necessary to clarify the precise role of probability theory in quantum mechanics, either as applied to, or as an intrinsic part of the quantum theory. When all is said and done the unsurprising conclusion is that quantum mechanics does not constitute a logic and probability unto itself, but adheres to the long-established rules of classical probability theory while providing a means within itself for calculating the relevant probabilities. In addition, the wavefunction is seen to be a description of the quantum state assigned by an observer based on definite information, such that the same state must be assigned by any other observer based on the same information, in much the same way that probabilities are assigned.

  14. Mind, matter and quantum mechanics

    CERN Document Server

    Stapp, Henry P

    2009-01-01

    "Scientists other than quantum physicists often fail to comprehend the enormity of the conceptual change wrought by quantum theory in our basic conception of the nature of matter," writes Henry Stapp. Stapp is a leading quantum physicist who has given particularly careful thought to the implications of the theory that lies at the heart of modern physics. In this book, which contains several of his key papers as well as new material, he focuses on the problem of consciousness and explains how quantum mechanics allows causally effective conscious thought to be combined in a natural way with the physical brain made of neurons and atoms. The book is divided into four sections. The first consists of an extended introduction. Key foundational and somewhat more technical papers are included in the second part, together with a clear exposition of the "orthodox" interpretation of quantum mechanics. The third part addresses, in a non-technical fashion, the implications of the theory for some of the most profound questi...

  15. Zeno dynamics in quantum statistical mechanics

    International Nuclear Information System (INIS)

    Schmidt, Andreas U

    2003-01-01

    We study the quantum Zeno effect in quantum statistical mechanics within the operator algebraic framework. We formulate a condition for the appearance of the effect in W*-dynamical systems, in terms of the short-time behaviour of the dynamics. Examples of quantum spin systems show that this condition can be effectively applied to quantum statistical mechanical models. Furthermore, we derive an explicit form of the Zeno generator, and use it to construct Gibbs equilibrium states for the Zeno dynamics. As a concrete example, we consider the X-Y model, for which we show that a frequent measurement at a microscopic level, e.g. a single lattice site, can produce a macroscopic effect in changing the global equilibrium

  16. Measurements and mathematical formalism of quantum mechanics

    Science.gov (United States)

    Slavnov, D. A.

    2007-03-01

    A scheme for constructing quantum mechanics is given that does not have Hilbert space and linear operators as its basic elements. Instead, a version of algebraic approach is considered. Elements of a noncommutative algebra (observables) and functionals on this algebra (elementary states) associated with results of single measurements are used as primary components of the scheme. On the one hand, it is possible to use within the scheme the formalism of the standard (Kolmogorov) probability theory, and, on the other hand, it is possible to reproduce the mathematical formalism of standard quantum mechanics, and to study the limits of its applicability. A short outline is given of the necessary material from the theory of algebras and probability theory. It is described how the mathematical scheme of the paper agrees with the theory of quantum measurements, and avoids quantum paradoxes.

  17. Philosophic foundations of quantum mechanics

    CERN Document Server

    Reichenbach, Hans

    1998-01-01

    Physics concerns direct analysis of the physical world, while philosophy analyzes knowledge about the physical world. This volume combines both disciplines for a philosophical interpretation of quantum physics - an interpretation free from the imprecision of metaphysics, offering a view of the atomic world and its quantum mechanical results as concrete as the visible everyday world.Written by an internationally renowned philosopher who specialized in symbolic logic and the theory of relativity, this approach consists of three parts. The first section, which requires no background in math or p

  18. Machine Learning and Quantum Mechanics

    Science.gov (United States)

    Chapline, George

    The author has previously pointed out some similarities between selforganizing neural networks and quantum mechanics. These types of neural networks were originally conceived of as away of emulating the cognitive capabilities of the human brain. Recently extensions of these networks, collectively referred to as deep learning networks, have strengthened the connection between self-organizing neural networks and human cognitive capabilities. In this note we consider whether hardware quantum devices might be useful for emulating neural networks with human-like cognitive capabilities, or alternatively whether implementations of deep learning neural networks using conventional computers might lead to better algorithms for solving the many body Schrodinger equation.

  19. Introduction to quantum statistical mechanics

    CERN Document Server

    Bogolyubov, N N

    2010-01-01

    Introduction to Quantum Statistical Mechanics (Second Edition) may be used as an advanced textbook by graduate students, even ambitious undergraduates in physics. It is also suitable for non experts in physics who wish to have an overview of some of the classic and fundamental quantum models in the subject. The explanation in the book is detailed enough to capture the interest of the reader, and complete enough to provide the necessary background material needed to dwell further into the subject and explore the research literature.

  20. Quantum Statistical Mechanics on a Quantum Computer

    OpenAIRE

    De Raedt, H.; Hams, A. H.; Michielsen, K.; Miyashita, S.; Saito, K.

    1999-01-01

    We describe a quantum algorithm to compute the density of states and thermal equilibrium properties of quantum many-body systems. We present results obtained by running this algorithm on a software implementation of a 21-qubit quantum computer for the case of an antiferromagnetic Heisenberg model on triangular lattices of different size.

  1. Making sense of quantum mechanics

    CERN Document Server

    Bricmont, Jean

    2016-01-01

    This book explains, in simple terms, with a minimum of mathematics, why things can appear to be in two places at the same time, why  correlations between simultaneous events occurring far apart cannot be explained by local mechanisms, and why, nevertheless, the quantum theory can be understood in terms of matter in motion. No need to worry, as some people do, whether a cat can be both dead and alive, whether the moon is there when nobody looks at it, or whether quantum systems need an observer to acquire definite properties. The author’s inimitable and even humorous style makes the book a pleasure to read while bringing a new clarity to many of the longstanding puzzles of quantum physics.

  2. Group Theoretical Approach for Controlled Quantum Mechanical Systems

    National Research Council Canada - National Science Library

    Tarn, Tzyh-Jong

    2007-01-01

    The aim of this research is the study of controllability of quantum mechanical systems and feedback control of de-coherence in order to gain an insight on the structure of control of quantum systems...

  3. Path Integrals in Quantum Mechanics

    International Nuclear Information System (INIS)

    Louko, J

    2005-01-01

    Jean Zinn-Justin's textbook Path Integrals in Quantum Mechanics aims to familiarize the reader with the path integral as a calculational tool in quantum mechanics and field theory. The emphasis is on quantum statistical mechanics, starting with the partition function Tr exp(-β H) and proceeding through the diffusion equation to barrier penetration problems and their semiclassical limit. The 'real time' path integral is defined via analytic continuation and used for the path-integral representation of the nonrelativistic S-matrix and its perturbative expansion. Holomorphic and Grassmannian path integrals are introduced and applied to nonrelativistic quantum field theory. There is also a brief discussion of path integrals in phase space. The introduction includes a brief historical review of path integrals, supported by a bibliography with some 40 entries. As emphasized in the introduction, mathematical rigour is not a central issue in the book. This allows the text to present the calculational techniques in a very readable manner: much of the text consists of worked-out examples, such as the quartic anharmonic oscillator in the barrier penetration chapter. At the end of each chapter there are exercises, some of which are of elementary coursework type, but the majority are more in the style of extended examples. Most of the exercises indeed include the solution or a sketch thereof. The book assumes minimal previous knowledge of quantum mechanics, and some basic quantum mechanical notation is collected in an appendix. The material has a large overlap with selected chapters in the author's thousand-page textbook Quantum Field Theory and Critical Phenomena (2002 Oxford: Clarendon). The stand-alone scope of the present work has, however, allowed a more focussed organization of this material, especially in the chapters on, respectively, holomorphic and Grassmannian path integrals. In my view the book accomplishes its aim admirably and is eminently usable as a textbook

  4. Phase space quantum mechanics and maximal acceleration

    International Nuclear Information System (INIS)

    Caianiello, E.

    1989-01-01

    My presentation is a synopsis of work done since 1979 in search of connections among information theory, systems theory, quantum mechanics and other matters. The aim was 'to extract geometry from quantum mechanics'. (orig./HSI)

  5. Quantum opto-mechanics with micromirrors : combining nano-mechanics with quantum optics

    International Nuclear Information System (INIS)

    Groeblacher, S.

    2010-01-01

    This work describes more than four years of research on the effects of the radiation-pressure force of light on macroscopic mechanical structures. The basic system studied here is a mechanical oscillator that is highly reflective and part of an optical resonator. It interacts with the optical cavity mode via the radiation-pressure force. Both the dynamics of the mechanical oscillation and the properties of the light field are modified through this interaction. In our experiments we use quantum optical tools (such as homodyning and down-conversion) with the goal of ultimately showing quantum behavior of the mechanical center of mass motion. In this thesis we present several experiments that pave the way towards this goal and when combined should allow the demonstration of the envisioned quantum phenomena, including entanglement, teleportation and Schroeodinger cat states. The study of quantum behavior of truly macroscopic systems is a long outstanding goal, which will help to answer some of the most fundamental questions in quantum physics today: Why is the world around us classical and not quantum? Is there a size- or mass-limit to systems for them to behave according to quantum mechanics? Is quantum theory complete or do we have to extend it to include mechanisms such as decoherence? Can we use the quantum nature of macroscopic objects to, for example, improve the measurement precision of classical apparatuses? The experiments discussed in this thesis include the very first passive radiation-pressure cooling of a mechanical oscillator in a cryogenic optical resonator, as well as the experimental demonstration of radiation-pressure cooling close to the mechanical quantum ground state. Cooling of the mechanical motion is an important pre-condition for observing quantum effects of the mechanical oscillator. In another experiment, we have demonstrated that we are able to enter the strong-coupling regime of the optomechanical system a regime where coherent energy

  6. Quantum mechanical study of solvent effects in a prototype SN2 reaction in solution: Cl- attack on CH3Cl.

    Science.gov (United States)

    Kuechler, Erich R; York, Darrin M

    2014-02-07

    The nucleophilic attack of a chloride ion on methyl chloride is an important prototype SN2 reaction in organic chemistry that is known to be sensitive to the effects of the surrounding solvent. Herein, we develop a highly accurate Specific Reaction Parameter (SRP) model based on the Austin Model 1 Hamiltonian for chlorine to study the effects of solvation into an aqueous environment on the reaction mechanism. To accomplish this task, we apply high-level quantum mechanical calculations to study the reaction in the gas phase and combined quantum mechanical/molecular mechanical simulations with TIP3P and TIP4P-ew water models and the resulting free energy profiles are compared with those determined from simulations using other fast semi-empirical quantum models. Both gas phase and solution results with the SRP model agree very well with experiment and provide insight into the specific role of solvent on the reaction coordinate. Overall, the newly parameterized SRP Hamiltonian is able to reproduce both the gas phase and solution phase barriers, suggesting it is an accurate and robust model for simulations in the aqueous phase at greatly reduced computational cost relative to comparably accurate ab initio and density functional models.

  7. Charge Carrier Conduction Mechanism in PbS Quantum Dot Solar Cells: Electrochemical Impedance Spectroscopy Study.

    Science.gov (United States)

    Wang, Haowei; Wang, Yishan; He, Bo; Li, Weile; Sulaman, Muhammad; Xu, Junfeng; Yang, Shengyi; Tang, Yi; Zou, Bingsuo

    2016-07-20

    With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells.

  8. Quantum mechanics of black holes.

    Science.gov (United States)

    Witten, Edward

    2012-08-03

    The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.

  9. Path Integrals in Quantum Mechanics

    International Nuclear Information System (INIS)

    Chetouani, L

    2005-01-01

    By treating path integrals the author, in this book, places at the disposal of the reader a modern tool for the comprehension of standard quantum mechanics. Thus the most important applications, such as the tunnel effect, the diffusion matrix, etc, are presented from an original point of view on the action S of classical mechanics while having it play a central role in quantum mechanics. What also emerges is that the path integral describes these applications more richly than are described traditionally by differential equations, and consequently explains them more fully. The book is certainly of high quality in all aspects: original in presentation, rigorous in the demonstrations, judicious in the choice of exercises and, finally, modern, for example in the treatment of the tunnel effect by the method of instantons. Moreover, the correspondence that exists between classical and quantum mechanics is well underlined. I thus highly recommend this book (the French version being already available) to those who wish to familiarize themselves with formulation by path integrals. They will find, in addition, interesting topics suitable for exploring further. (book review)

  10. Dynamical parasupersymmetries in quantum mechanics

    International Nuclear Information System (INIS)

    Durand, S.; Vinet, L.

    1990-01-01

    This paper reports on supersymmetric field theories that have the distinctive feature of being invariant under transformations that mix bosonic and fermionic variables. Reduction to 0 + 1 dimensions yields mechanical models with an analogous invariance. In this case, the Grassmannian variables are interpreted as describing (classically) the spin degrees of freedom of the particles involved. After canonical quantization, the corresponding quantities obey the standard anticommutation relations of fermionic creation and annihilation operators. It is known that paraquantitization offers alternative to the usual quantization scheme. In this framework, one can expect that it is possible to construct parasupersymmetric theories, that is, theories which are invariant under transformations between bosonic and parafermionic variables. As a matter of fact, Rubakov and Spiridonov has recently shown how the parasupersymmetric generalization of supersymmetric Quantum Mechanics proceeds. In this case, the fermionic creation and annihilation operators obey paracommutation relations. The applications of supersymmetric Quantum Mechanics are many. One might hope that its parasupersymmetric generalization will be as useful. The elaboration of parasupersymmeric Quantum Mechanics moreover has led to new mathematical constructs; indeed, the symmetry generators realize algebras involving products of degree higher than 2

  11. Three-space from quantum mechanics

    International Nuclear Information System (INIS)

    Chew, G.F.; Stapp, H.P.

    1988-01-01

    We formulate a discrete quantum-mechanical precursor to spacetime geometry. The objective is to provide the foundation for a quantum mechanics that is rooted exclusively in quantum-mechanical concepts, with all classical features, including the three-dimensional spatial continuum, emerging dynamically

  12. Introductory quantum mechanics for applied nanotechnology

    CERN Document Server

    Kim, Dae Mann

    2015-01-01

    This introductory textbook covers fundamental quantum mechanics from an application perspective, considering optoelectronic devices, biological sensors and molecular imagers as well as solar cells and field effect transistors. The book provides a brief review of classical and statistical mechanics and electromagnetism, and then turns to the quantum treatment of atoms, molecules, and chemical bonds. Aiming at senior undergraduate and graduate students in nanotechnology related areas like physics, materials science, and engineering, the book could be used at schools that offer interdisciplinary but focused training for future workers in the semiconductor industry and for the increasing number of related nanotechnology firms, and even practicing people could use it when they need to learn related concepts. The author is Professor Dae Mann Kim from the Korea Institute for Advanced Study who has been teaching Quantum Mechanics to engineering, material science and physics students for over 25 years in USA and Asia.

  13. The birth of quantum mechanics

    International Nuclear Information System (INIS)

    Mehra, J.

    1976-01-01

    In an attempt to give an exact mathematical formulation of Bohr's Correspondence Principle, Heisenberg (June 1925) discovered the rules governing the behaviour of quantum- theoretical magnitudes. In fall 1925 Born, Heisenberg and Jordan and, independently, Dirac, formulated consistent algebraic schemes of quantum mechanics. Early in 1926 Schroedinger developed wave mechanics. In quick succession were discovered: Born's probability interpretation of the wave function, the transformation theory of Dirac, Jordan and F. London, Heisenberg's Uncertainty Relations and Bohr's Principle of Complementarity. By September 1927 the basis of a complete theory of atomic phenomena had been established. Aspects of this development, in which Heisenberg played a central role, are presented here as a tribute to his memory. (Author)

  14. Quantum mechanics from general relativity

    International Nuclear Information System (INIS)

    Sachs, M.

    1986-01-01

    A generalization of quantum mechanics is demonstrated in the context of general relativity, following from a generally covariant field theory of inertia. Nonrelativistically, the formalism corresponds with linear quantum mechanics. In the limit of special relativity, nonlinearity remains and several new features are derived: (1) Particle-antiparticle pairs do not annihilate; an exact bound state solution is derived corresponding with all experimental facts about annihilation/creation - which, in approximation, gives the blackbody radiation spectrum for a sea of such pairs. (2) A result is proven, without approximation, that is physically equivalent to the Pauli exclusion principle - which, in linear approximation, gives the totally antisymmetrised many-body wave function and Fermi-Dirac statistics. (3) The hydrogen spectrum is derived, including the Lamb shifts, in agreement with experiment; new results are found for high energy electron-proton scattering. (4) Finally, several applications to the elementary particle domain are demonstrated, in agreement with results from experimental high energy physics. (Auth.)

  15. Quantum mechanics on noncommutative spacetime

    International Nuclear Information System (INIS)

    Calmet, Xavier; Selvaggi, Michele

    2006-01-01

    We consider electrodynamics on a noncommutative spacetime using the enveloping algebra approach and perform a nonrelativistic expansion of the effective action. We obtain the Hamiltonian for quantum mechanics formulated on a canonical noncommutative spacetime. An interesting new feature of quantum mechanics formulated on a noncommutative spacetime is an intrinsic electric dipole moment. We note, however, that noncommutative intrinsic dipole moments are not observable in present experiments searching for an electric dipole moment of leptons or nuclei such as the neutron since they are spin independent. These experiments are sensitive to the energy difference between two states and the noncommutative effect thus cancels out. Bounds on the noncommutative scale found in the literature relying on such intrinsic electric dipole moments are thus incorrect

  16. On quantum mechanics for macroscopic systems

    International Nuclear Information System (INIS)

    Primas, H.

    1992-01-01

    The parable of Schroedinger's cat may lead to several up-to date questions: how to treat open systems in quantum theory, how to treat thermodynamically irreversible processes in the quantum mechanics framework, how to explain, following the quantum theory, the existence, phenomenologically evident, of classical observables, what implies the predicted existence by the quantum theory of non localized macroscopic material object ?

  17. Substantiating problems of quantum mechanics

    International Nuclear Information System (INIS)

    Gottlieb, J.

    1978-05-01

    Some basic problems, related to the spaces and the operators necessary to describe quantum-mechanical phenomena, are entered upon from a new axiomatic standpoint. Some generalizations are operated, required by convergence criteria, concerning the Fourier transform, the Fourier product and the equation of eigen-values. Physical arguments are brought to support such generalizations and an analysis in view of organizing the structure of the proposed spaces is undertaken. (author)

  18. Supersymmetric quantum mechanics an introduction

    CERN Document Server

    Gangopadhyaya, Asim; Rasinariu, Constantin

    2017-01-01

    We have written this book in order to provide a single compact source for undergraduate and graduate students, as well as for professional physicists who want to understand the essentials of supersymmetric quantum mechanics. It is an outgrowth of a seminar course taught to physics and mathematics juniors and seniors at Loyola University Chicago, and of our own research over a quarter of a century.

  19. Quantum mechanics new approaches to selected topics

    CERN Document Server

    Lipkin, Harry Jeannot

    1973-01-01

    Acclaimed as ""excellent"" (Nature) and ""very original and refreshing"" (Physics Today), this collection of self-contained studies is geared toward advanced undergraduates and graduate students. Its broad selection of topics includes the Mössbauer effect, many-body quantum mechanics, scattering theory, Feynman diagrams, and relativistic quantum mechanics.Author Harry J. Lipkin, a well-known teacher at Israel's Weizmann Institute, takes an unusual approach by introducing many interesting physical problems and mathematical techniques at a much earlier point than in conventional texts. This meth

  20. ''Topological'' (Chern-Simons) quantum mechanics

    International Nuclear Information System (INIS)

    Dunne, G.V.; Jackiw, R.; Trugenberger, C.A.

    1990-01-01

    We construct quantum-mechanical models that are analogs of three-dimensional, topologically massive as well as Chern-Simons gauge-field theories, and we study the phase-space reductive limiting procedure that takes the former to the latter. The zero-point spectra of operators behave discontinuously in the limit, as a consequence of a nonperturbative quantum-mechanical anomaly. The nature of the limit for wave functions depends on the representation, but is always such that normalization is preserved

  1. The formalisms of quantum mechanics an introduction

    CERN Document Server

    David, Francois

    2015-01-01

    These lecture notes present a concise and introductory, yet as far as possible coherent, view of the main formalizations of quantum mechanics and of quantum field theories, their interrelations and their theoretical foundations. The “standard” formulation of quantum mechanics (involving the Hilbert space of pure states, self-adjoint operators as physical observables, and the probabilistic interpretation given by the Born rule) on one hand, and the path integral and functional integral representations of probabilities amplitudes on the other, are the standard tools used in most applications of quantum theory in physics and chemistry. Yet, other mathematical representations of quantum mechanics sometimes allow better comprehension and justification of quantum theory. This text focuses on two of such representations: the algebraic formulation of quantum mechanics and the “quantum logic” approach. Last but not least, some emphasis will also be put on understanding the relation between quantum physics and ...

  2. Quantum mechanics/molecular mechanics studies on the mechanism of action of cofactor pyridoxal 5'-phosphate in ornithine 4,5-aminomutase.

    Science.gov (United States)

    Pang, Jiayun; Scrutton, Nigel S; Sutcliffe, Michael J

    2014-09-01

    A computational study was performed on the experimentally elusive cyclisation step in the cofactor pyridoxal 5'-phosphate (PLP)-dependent D-ornithine 4,5-aminomutase (OAM)-catalysed reaction. Calculations using both model systems and a combined quantum mechanics/molecular mechanics approach suggest that regulation of the cyclic radical intermediate is achieved through the synergy of the intrinsic catalytic power of cofactor PLP and the active site of the enzyme. The captodative effect of PLP is balanced by an enzyme active site that controls the deprotonation of both the pyridine nitrogen atom (N1) and the Schiff-base nitrogen atom (N2). Furthermore, electrostatic interactions between the terminal carboxylate and amino groups of the substrate and Arg297 and Glu81 impose substantial "strain" energy on the orientation of the cyclic intermediate to control its trajectory. In addition the "strain" energy, which appears to be sensitive to both the number of carbon atoms in the substrate/analogue and the position of the radical intermediates, may play a key role in controlling the transition of the enzyme from the closed to the open state. Our results provide new insights into several aspects of the radical mechanism in aminomutase catalysis and broaden our understanding of cofactor PLP-dependent reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Quantum Mechanics: Fundamentals; Advanced Quantum Mechanics; Mathematical Concepts of Quantum Mechanics

    International Nuclear Information System (INIS)

    Whitaker, A

    2004-01-01

    This review is of three books, all published by Springer, all on quantum theory at a level above introductory, but very different in content, style and intended audience. That of Gottfried and Yan is of exceptional interest, historical and otherwise. It is a second edition of Gottfried's well-known book published by Benjamin in 1966. This was written as a text for a graduate quantum mechanics course, and has become one of the most used and respected accounts of quantum theory, at a level mathematically respectable but not rigorous. Topics absent from the first edition but included in the second include the Feynman path integral, seen in 1966 as an imaginative but not very useful formulation of quantum theory. Feynman methods were given only a cursory mention by Gottfried. Other new topics include semiclassical quantum mechanics, motion in a magnetic field, the S matrix and inelastic collisions, radiation and scattering of light, identical particle systems and the Dirac equation. A topic that was all but totally neglected in 1966, but which has flourished increasingly since, is that of the foundations of quantum theory. To commence with general discussion of the new book, the authors recognise that the graduate student of today almost certainly has substantial experience of wave mechanics, and is probably familiar with the Dirac formalism. The new edition has been almost entirely rewritten; even at the level of basic text, it is difficult to trace sentences or paragraphs that have moved unscathed from one edition to the next. As well as the new topics, many of the old ones are discussed in much greater depth, and the general organisation is entirely different. As compared with the steady rise in level of the 1966 edition, the level of this book is fairly consistent throughout, and from the perspective of a beginning graduate student, I would estimate, a little tough. To sum up, Gottfried and Yan's book contains a vast amount of knowledge and understanding. The

  4. Faster than Hermitian Quantum Mechanics

    International Nuclear Information System (INIS)

    Bender, Carl M.; Brody, Dorje C.; Jones, Hugh F.; Meister, Bernhard K.

    2007-01-01

    Given an initial quantum state vertical bar ψ I > and a final quantum state vertical bar ψ F >, there exist Hamiltonians H under which vertical bar ψ I > evolves into vertical bar ψ F >. Consider the following quantum brachistochrone problem: subject to the constraint that the difference between the largest and smallest eigenvalues of H is held fixed, which H achieves this transformation in the least time τ? For Hermitian Hamiltonians τ has a nonzero lower bound. However, among non-Hermitian PT-symmetric Hamiltonians satisfying the same energy constraint, τ can be made arbitrarily small without violating the time-energy uncertainty principle. This is because for such Hamiltonians the path from vertical bar ψ I > to vertical bar ψ F > can be made short. The mechanism described here is similar to that in general relativity in which the distance between two space-time points can be made small if they are connected by a wormhole. This result may have applications in quantum computing

  5. Quantum information aspects of noncommutative quantum mechanics

    Science.gov (United States)

    Bertolami, Orfeu; Bernardini, Alex E.; Leal, Pedro

    2018-01-01

    Some fundamental aspects related with the construction of Robertson-Schrödinger-like uncertainty-principle inequalities are reported in order to provide an overall description of quantumness, separability and nonlocality of quantum systems in the noncommutative phase-space. Some consequences of the deformed noncommutative algebra are also considered in physical systems of interest.

  6. ELECTROREDUCTION MECHANISM OF Ni(DMG)-2 COMPLEX STUDIED WITH QUANTUM CHEMICAL METHOD

    Institute of Scientific and Technical Information of China (English)

    倪亚明; 任镜清; 黎健; 王德民; 梁伟根; 朱芝仙; 高小霞

    1990-01-01

    The electronic structures of the species Ni(DMG)2, (Ni(DMG)2)- and (Ni(DMG)2)2- have been studied by INDO quantum chemical method. The results have clearly shown that in the first stage of the electroreduction of Ni(DMG)2, one electron interacts with the d orbitals on the nickel atom, while in the further stage the second electron interacts with the p orbitals on the nitrogen atoms. It conforms with our electrochemical experimental studies which showed that not only Ni(Ⅱ) is reduced but also DMG is catalytically reduced during the reduction of Ni(DMG)2.

  7. Structural study of piracetam polymorphs and cocrystals: crystallography redetermination and quantum mechanics calculations.

    Science.gov (United States)

    Tilborg, Anaëlle; Jacquemin, Denis; Norberg, Bernadette; Perpète, Eric; Michaux, Catherine; Wouters, Johan

    2011-12-01

    Pharmaceutical compounds are mostly developed as solid dosage forms containing a single-crystal form. It means that the selection of a particular crystal state for a given molecule is an important step for further clinical outlooks. In this context, piracetam, a pharmaceutical molecule known since the sixties for its nootropic properties, is considered in the present work. This molecule is analyzed using several experimental and theoretical approaches. First, the conformational space of the molecule has been systematically explored by performing a quantum mechanics scan of the two most relevant dihedral angles of the lateral chain. The predicted stable conformations have been compared to all the reported experimental geometries retrieved from the Cambridge Structural Database (CSD) covering polymorphs and cocrystals structures. In parallel, different batches of powders have been recrystallized. Under specific conditions, single crystals of polymorph (III) of piracetam have been obtained, an outcome confirmed by crystallographic analysis. © 2011 International Union of Crystallography. Printed in Singapore – all rights reserved.

  8. Annotations to quantum statistical mechanics

    CERN Document Server

    Kim, In-Gee

    2018-01-01

    This book is a rewritten and annotated version of Leo P. Kadanoff and Gordon Baym’s lectures that were presented in the book Quantum Statistical Mechanics: Green’s Function Methods in Equilibrium and Nonequilibrium Problems. The lectures were devoted to a discussion on the use of thermodynamic Green’s functions in describing the properties of many-particle systems. The functions provided a method for discussing finite-temperature problems with no more conceptual difficulty than ground-state problems, and the method was equally applicable to boson and fermion systems and equilibrium and nonequilibrium problems. The lectures also explained nonequilibrium statistical physics in a systematic way and contained essential concepts on statistical physics in terms of Green’s functions with sufficient and rigorous details. In-Gee Kim thoroughly studied the lectures during one of his research projects but found that the unspecialized method used to present them in the form of a book reduced their readability. He st...

  9. Quantum mechanics from elementary view

    International Nuclear Information System (INIS)

    Fischer, Karl

    2009-01-01

    This book offers an introduction to quantum mechanics as well as interesting supplements up to the beginnings of quantum field theory. A comprehensive mathematical block facilitates the access. It is rich on examples and otherwise mostly not findable calculations, which make it so transparent in its results. It likes the historical relations and brings so the feeling how much has been grown from the past. It brings also a short outline about relativity theory up to the understanding of the term ''metrics''. The spotlight holds the term product space, by means of which quantum mechanics is put together to a practicable theory. A simpler notation for instance at the Dirac equation facilitates also the understanding. On the mathematical side it is above all the term distributive law as well as the term linear combination, which lead so simple transparent definitions fast to more general. Generally it is tried to find an as possible elementary access to at least not elementary connections. So may it be for many both instructive and interesting

  10. Insights into the Lactonase Mechanism of Serum Paraoxonase 1 (PON1): Experimental and Quantum Mechanics/Molecular Mechanics (QM/MM) Studies.

    Science.gov (United States)

    Le, Quang Anh Tuan; Kim, Seonghoon; Chang, Rakwoo; Kim, Yong Hwan

    2015-07-30

    Serum paraoxonase 1 (PON1) is a versatile enzyme for the hydrolysis of various substrates (e.g., lactones, phosphotriesters) and for the formation of a promising chemical platform γ-valerolactone. Elucidation of the PON1-catalyzed lactonase reaction mechanism is very important for understanding the enzyme function and for engineering this enzyme for specific applications. Kinetic study and hybrid quantum mechanics/molecular mechanics (QM/MM) method were used to investigate the PON1-catalyzed lactonase reaction of γ-butyrolactone (GBL) and (R)-γ-valerolactone (GVL). The activation energies obtained from the QM/MM calculations were in good agreement with the experiments. Interestingly, the QM/MM energy barriers at MP2/3-21G(d,p) level for the lactonase of GVL and GBL were respectively 14.3-16.2 and 11.5-13.1 kcal/mol, consistent with the experimental values (15.57 and 14.73 kcal/mol derived from respective kcat values of 36.62 and 147.21 s(-1)). The QM/MM energy barriers at MP2/6-31G(d) and MP2/6-31G(d,p) levels were also in relatively good agreements with the experiments. Importantly, the difference in the QM/MM energy barriers at MP2 level with all investigated basis sets for the lactonase of GVL and GBL were in excellent agreement with the experiments (0.9-3.1 and 0.8 kcal/mol, respectively). A detailed mechanism for the PON1-catalyzed lactonase reaction was also proposed in this study.

  11. Completing Quantum Mechanics with Quantized Hidden Variables

    OpenAIRE

    van Enk, S. J.

    2015-01-01

    I explore the possibility that a quantum system S may be described completely by the combination of its standard quantum state $|\\psi\\rangle$ and a (hidden) quantum state $|\\phi\\rangle$ (that lives in the same Hilbert space), such that the outcome of any standard projective measurement on the system S is determined once the two quantum states are specified. I construct an algorithm that retrieves the standard quantum-mechanical probabilities, which depend only on $|\\psi\\rangle$, by assuming t...

  12. Teaching Quantum Mechanics on an Introductory Level.

    Science.gov (United States)

    Muller, Rainer; Wiesner, Hartmut

    2002-01-01

    Presents a new research-based course on quantum mechanics in which the conceptual issues of quantum mechanics are taught at an introductory level. Involves students in the discovery of how quantum phenomena deviate from classical everyday experiences. (Contains 31 references.) (Author/YDS)

  13. Quantum mechanics and hidden superconformal symmetry

    Science.gov (United States)

    Bonezzi, R.; Corradini, O.; Latini, E.; Waldron, A.

    2017-12-01

    Solvability of the ubiquitous quantum harmonic oscillator relies on a spectrum generating osp (1 |2 ) superconformal symmetry. We study the problem of constructing all quantum mechanical models with a hidden osp (1 |2 ) symmetry on a given space of states. This problem stems from interacting higher spin models coupled to gravity. In one dimension, we show that the solution to this problem is the Vasiliev-Plyushchay family of quantum mechanical models with hidden superconformal symmetry obtained by viewing the harmonic oscillator as a one dimensional Dirac system, so that Grassmann parity equals wave function parity. These models—both oscillator and particlelike—realize all possible unitary irreducible representations of osp (1 |2 ).

  14. Limits to the universality of quantum mechanics

    International Nuclear Information System (INIS)

    Josephson, B.D.

    1988-01-01

    Niels Bohr's arguments indicating the non-applicability of quantum methodology to the study of the ultimate details of life, given in his book Atomic Physics and Human Knowledge, conflict with the commonly held opposite view. The bases for the usual beliefs are examined and shown to have little validity; significant differences do exist between the living organism and the type of system studied successfully in the physics laboratory. Dealing with living organisms in quantum-mechanical terms with the same degree of rigor as is normal for non-living systems would seem not to be possible without considering also questions of the origins of life and of the universe

  15. Photophysics and Photochemistry of Canonical Nucleobases’ Thioanalogs: From Quantum Mechanical Studies to Time Resolved Experiments

    Directory of Open Access Journals (Sweden)

    Serra Arslancan

    2017-06-01

    Full Text Available Interest in understanding the photophysics and photochemistry of thiated nucleobases has been awakened because of their possible involvement in primordial RNA or their potential use as photosensitizers in medicinal chemistry. The interpretation of the photodynamics of these systems, conditioned by their intricate potential energy surfaces, requires the powerful interplay between experimental measurements and state of the art molecular simulations. In this review, we provide an overview on the photophysics of natural nucleobases’ thioanalogs, which covers the last 30 years and both experimental and computational contributions. For all the canonical nucleobase’s thioanalogs, we have compiled the main steady state absorption and emission features and their interpretation in terms of theoretical calculations. Then, we revise the main topographical features, including stationary points and interstate crossings, of their potential energy surfaces based on quantum mechanical calculations and we conclude, by combining the outcome of different spectroscopic techniques and molecular dynamics simulations, with the mechanism by which these nucleobase analogs populate their triplet excited states, which are at the origin of their photosensitizing properties.

  16. Entropy, Topological Theories and Emergent Quantum Mechanics

    Directory of Open Access Journals (Sweden)

    D. Cabrera

    2017-02-01

    Full Text Available The classical thermostatics of equilibrium processes is shown to possess a quantum mechanical dual theory with a finite dimensional Hilbert space of quantum states. Specifically, the kernel of a certain Hamiltonian operator becomes the Hilbert space of quasistatic quantum mechanics. The relation of thermostatics to topological field theory is also discussed in the context of the approach of the emergence of quantum theory, where the concept of entropy plays a key role.

  17. A 'general boundary' formulation for quantum mechanics and quantum gravity

    International Nuclear Information System (INIS)

    Oeckl, Robert

    2003-01-01

    I propose to formalize quantum theories as topological quantum field theories in a generalized sense, associating state spaces with boundaries of arbitrary (and possibly finite) regions of space-time. I further propose to obtain such 'general boundary' quantum theories through a generalized path integral quantization. I show how both, non-relativistic quantum mechanics and quantum field theory can be given a 'general boundary' formulation. Surprisingly, even in the non-relativistic case, features normally associated with quantum field theory emerge from consistency conditions. This includes states with arbitrary particle number and pair creation. I also note how three-dimensional quantum gravity is an example for a realization of both proposals and suggest to apply them to four-dimensional quantum gravity

  18. Supersymmetric Quantum Mechanics and Topology

    International Nuclear Information System (INIS)

    Wasay, Muhammad Abdul

    2016-01-01

    Supersymmetric quantum mechanical models are computed by the path integral approach. In the β→0 limit, the integrals localize to the zero modes. This allows us to perform the index computations exactly because of supersymmetric localization, and we will show how the geometry of target space enters the physics of sigma models resulting in the relationship between the supersymmetric model and the geometry of the target space in the form of topological invariants. Explicit computation details are given for the Euler characteristics of the target manifold and the index of Dirac operator for the model on a spin manifold.

  19. Quantum mechanics and umbral calculus

    International Nuclear Information System (INIS)

    Lopez-Sendino, J E; Negro, J; Olmo, M A del; Salgado, E

    2008-01-01

    In this paper we present the first steps for obtaining a discrete Quantum Mechanics making use of the Umbral Calculus. The idea is to discretize the continuous Schroedinger equation substituting the continuous derivatives by discrete ones and the space-time continuous variables by well determined operators that verify some Umbral Calculus conditions. In this way we assure that some properties of integrability and symmetries of the continuous equation are preserved and also the solutions of the continuous case can be recovered discretized in a simple way. The case of the Schroedinger equation with a potential depending only in the space variable is discussed.

  20. A catastrophe in quantum mechanics

    International Nuclear Information System (INIS)

    Ignatovich, V.K.

    2004-01-01

    The standard scattering theory (SST) in nonrelativistic quantum mechanics (QM) is analyzed. Self-contradictions of SST are deconstructed. A direct way to calculate scattering probability without introduction of a finite volume is discussed. Substantiation of SST in textbooks with the help of wave packets is shown to be incomplete. A complete theory of wave packet scattering on a fixed center is presented, and its similarity to the plane wave scattering is demonstrated. The neutron scattering on a monatomic gas is investigated, and several problems are pointed out. A catastrophic ambiguity of the cross section is revealed, and a way to resolve this ambiguity is discussed

  1. Pseudo-Hermitian Representation of Quantum Mechanics

    International Nuclear Information System (INIS)

    Mustafazade, A.

    2008-01-01

    I will outline a formulation of quantum mechanics in which the inner product on the Hilbert space of a quantum system is treated as a degree of freedom. I will outline some of the basic mathematical and conceptual features of the resulting theory and discuss some of its applications. In particular, I will present a quantum mechanical analogue of Einstein's field equations that links the inner product of the Hilbert space and the Hamiltonian of the system and discuss how the resulting theory can be used to address a variety of problems in classical electrodynamics, relativistic quantum mechanics, and quantum computation

  2. Quantum mechanics for applied physics and engineering

    CERN Document Server

    Fromhold, Albert T

    2011-01-01

    This excellent text, directed to upper-level undergraduates and graduate students in engineering and applied physics, introduces the fundamentals of quantum mechanics, emphasizing those aspects of quantum mechanics and quantum statistics essential to an understanding of solid-state theory. A heavy background in mathematics and physics is not required beyond basic courses in calculus, differential equations, and calculus-based elementary physics.The first three chapters introduce quantum mechanics (using the Schrödinger equations), quantum statistics, and the free-electron theory of metals. Ch

  3. Stochastic quantum mechanics and quantum spacetime

    International Nuclear Information System (INIS)

    Prugovecki, E.

    1984-01-01

    This monograph's principal intent is to provide a systematic and self-contained introduction to an alternative unification of relativity with quantum theory based on stochastic phase spaces and stochastic geometries, and presented at a level accessible to graduate students in theoretical and mathematical physics as well as to professional physicists and mathematicians. The proposed framework for unification embraces classical as well as quantum theories by implementing an epistemic idea first put forth by M. Born, namely that all physical theories should be formulated in terms of stochastic rather than deterministic values for measurable quantities. The framework gives rise to a whole range of yet unresearched problems, whose solutions are bound to shed some light on the relationship between relativity and quantum theories of the most fundamental physical and mathematical levels. (Auth.)

  4. The emerging quantum the physics behind quantum mechanics

    CERN Document Server

    Pena, Luis de la; Valdes-Hernandez, Andrea

    2014-01-01

    This monograph presents the latest findings from a long-term research project intended to identify the physics behind Quantum Mechanics. A fundamental theory for quantum mechanics is constructed from first physical principles, revealing quantization as an emergent phenomenon arising from a deeper stochastic process. As such, it offers the vibrant community working on the foundations of quantum mechanics an alternative contribution open to discussion. The book starts with a critical summary of the main conceptual problems that still beset quantum mechanics.  The basic consideration is then introduced that any material system is an open system in permanent contact with the random zero-point radiation field, with which it may reach a state of equilibrium. Working from this basis, a comprehensive and self-consistent theoretical framework is then developed. The pillars of the quantum-mechanical formalism are derived, as well as the radiative corrections of nonrelativistic QED, while revealing the underlying physi...

  5. Quantum mechanics in complex systems

    Science.gov (United States)

    Hoehn, Ross Douglas

    This document should be considered in its separation; there are three distinct topics contained within and three distinct chapters within the body of works. In a similar fashion, this abstract should be considered in three parts. Firstly, we explored the existence of multiply-charged atomic ions by having developed a new set of dimensional scaling equations as well as a series of relativistic augmentations to the standard dimensional scaling procedure and to the self-consistent field calculations. Secondly, we propose a novel method of predicting drug efficacy in hopes to facilitate the discovery of new small molecule therapeutics by modeling the agonist-protein system as being similar to the process of Inelastic Electron Tunneling Spectroscopy. Finally, we facilitate the instruction in basic quantum mechanical topics through the use of quantum games; this method of approach allows for the generation of exercises with the intent of conveying the fundamental concepts within a first year quantum mechanics classroom. Furthermore, no to be mentioned within the body of the text, yet presented in appendix form, certain works modeling the proliferation of cells types within the confines of man-made lattices for the purpose of facilitating artificial vascular transplants. In Chapter 2, we present a theoretical framework which describes multiply-charged atomic ions, their stability within super-intense laser fields, also lay corrections to the systems due to relativistic effects. Dimensional scaling calculations with relativistic corrections for systems: H, H-, H 2-, He, He-, He2-, He3- within super-intense laser fields were completed. Also completed were three-dimensional self consistent field calculations to verify the dimensionally scaled quantities. With the aforementioned methods the system's ability to stably bind 'additional' electrons through the development of multiple isolated regions of high potential energy leading to nodes of high electron density is shown

  6. Tunneling time in space fractional quantum mechanics

    Science.gov (United States)

    Hasan, Mohammad; Mandal, Bhabani Prasad

    2018-02-01

    We calculate the time taken by a wave packet to travel through a classically forbidden region of space in space fractional quantum mechanics. We obtain the close form expression of tunneling time from a rectangular barrier by stationary phase method. We show that tunneling time depends upon the width b of the barrier for b → ∞ and therefore Hartman effect doesn't exist in space fractional quantum mechanics. Interestingly we found that the tunneling time monotonically reduces with increasing b. The tunneling time is smaller in space fractional quantum mechanics as compared to the case of standard quantum mechanics. We recover the Hartman effect of standard quantum mechanics as a special case of space fractional quantum mechanics.

  7. Quantum mechanics, relativity and casuality

    International Nuclear Information System (INIS)

    Tati, T.

    1976-01-01

    In quantum mechanics, the state is prepared by a measurement on a spacelike surface sigma. What is that determine the surface sigma on which the measurement prepares the stae. It si considered either a mechanism proper to the measuring process (apparatus) or a universal property of space-time. In the former case, problems arise, concerning casuality or conservation of probability due to the fact that the velocity of reduction of a wave packet is considered to exceed the light velocity. The theory of finite degree of freedom proposed previously belongs to the latter case. In this theory, the surface sigma is restricted to the hyper-plane perpendicular to a universal time-like vector governing casual relations. An experimental to discriminate between the above-mentioned two cases and to test the existence of the universal timelike vector is proposed

  8. Quantum mechanics, relativity and causality

    International Nuclear Information System (INIS)

    Tati, Takao.

    1975-07-01

    In quantum mechanics, the state is prepared by a measurement on a space-like surface sigma. What is that determines the surface sigma on which the measurement prepares the state It is considered either a mechanism proper to the measuring process (apparatus) or a universal property of space-time. In the former case, problems arise, concerning causality or conservation of probability due to that the velocity of reduction of wave-packet is considered to exceed the light velocity. The theory of finite degree of freedom proposed previously belongs to the latter case. In this theory, the surface sigma is restricted to the hyper-plane perpendicular to a universal time-like vector governing causal relations. We propose an experiment to discriminate between the above-mentioned two cases and to test the existence of the universal time-like vector. (auth.)

  9. Introductory quantum mechanics for semiconductor nanotechnology

    International Nuclear Information System (INIS)

    Kim, Dae Mann

    2010-01-01

    The result of the nano education project run by the Korean Nano Technology Initiative, this has been recommended for use as official textbook by the Korean Nanotechnology Research Society. The author is highly experienced in teaching both physics and engineering in academia and industry, and naturally adopts an interdisciplinary approach here. He is short on formulations but long on applications, allowing students to understand the essential workings of quantum mechanics without spending too much time covering the wide realms of physics. He takes care to provide sufficient technical background and motivation for students to pursue further studies of advanced quantum mechanics and stresses the importance of translating quantum insights into useful and tangible innovations and inventions. As such, this is the only work to cover semiconductor nanotechnology from the perspective of introductory quantum mechanics, with applications including mainstream semiconductor technologies as well as (nano)devices, ranging from photodetectors, laser diodes, and solar cells to transistors and Schottky contacts. Problems are also provided to test the reader's understanding and supplementary material available includes working presentation files, solutions and instructors manuals. (orig.)

  10. Testing the foundations of quantum mechanics

    CERN Document Server

    Gisin, Nicolas; CERN. Geneva

    1999-01-01

    Quantum mechanics is certainly one of the most fascinating field of physics. In recent years, the new field of "quantum information processing" based on the most fundamental aspect of quantum mechanics, like linearity and entanglement, even increased and its peculiarities. In this series of 4 lectures we shall present some of the issues and experiments that test quantum theory. Entanglement leads, on the one hand side, to the measurement problem, to the EPR paradox and to quantum nonlocality ( distant systems). We will derive the Bell inequality, present experimental results that provide huge evidence in favor of quantum nonlocality and discuss some loopholes that are still open. On the other side, entanglement offers many new possibilities for information processing. Indeed, it provides means to carry out tasks that are either impossible classically (like quantum cryptography and quantum teleportation) or that would require significantly more steps to perform on a classical computer (like searching a databas...

  11. The Picture Book of Quantum Mechanics

    CERN Document Server

    Brandt, Siegmund

    2012-01-01

    The aim of this book is to explain the basic concepts and phenomena of quantum mechanics by means of visualization. Computer-generated illustrations in color are used extensively throughout the text, helping to establish the relation between quantum mechanics—wave functions, interference, atomic structure, and so forth—and classical physics—point mechanics, statistical mechanics, and wave optics. Even more important, by studying the pictures in parallel with the text, readers develop an intuition for such notoriously abstract phenomena as • the tunnel effect • excitation and decay of metastable states • wave-packet motion within a well • systems of distinguishable and indistinguishable particles • free wave packets and scattering in 3 dimensions • angular-momentum decomposition • stationary bound states in various 3-dimensional potentials • hybrid states • Kepler motion of wave packets in the Coulomb field • spin and magnetic resonance Illustrations from experiments in a variety of f...

  12. Search for violations of quantum mechanics

    International Nuclear Information System (INIS)

    Ellis, J.; Hagelin, J.S.; Nanopoulos, D.V.; Srednicki, M.

    1984-01-01

    The treatment of quantum effects in gravitational fields indicates that pure states may evolve into mixed states, and Hawking has proposed modification of the axioms of field theory which incorporate the corresponding violation of quantum mechanics. In this paper we propose a modified hamiltonian equation of motion for density matrices and use it to interpret upper bounds on the violation of quantum mechanics in different phenomenological situations. We apply our formalism to the K 0 -anti K 0 system and to long baseline neutron interferometry experiments. In both cases we find upper bounds of about 2x10 -21 GeV on contributions to the single particle 'hamiltonian' which violate quantum mechanical coherence. We discuss how these limits might be improved in the future, and consider the relative significance of other successful tests of quantum mechanics. An appendix contains model estimates of the magnitude of effects violating quantum mechanics. (orig.)

  13. A Bit of Quantum Mechanics

    Science.gov (United States)

    Oss, Stefano; Rosi, Tommaso

    2015-04-01

    We have developed an app for iOS-based smart-phones/tablets that allows a 3-D, complex phase-based colorful visualization of hydrogen atom wave functions. Several important features of the quantum behavior of atomic orbitals can easily be made evident, thus making this app a useful companion in introductory modern physics classes. There are many reasons why quantum mechanical systems and phenomena are difficult both to teach and deeply understand. They are described by equations that are generally hard to visualize, and they often oppose the so-called "common sense" based on the human perception of the world, which is built on mental images such as locality and causality. Moreover students cannot have direct experience of those systems and solutions, and generally do not even have the possibility to refer to pictures, videos, or experiments to fill this gap. Teachers often encounter quite serious troubles in finding out a sensible way to speak about the wonders of quantum physics at the high school level, where complex formalisms are not accessible at all. One should however consider that this is quite a common issue in physics and, more generally, in science education. There are plenty of natural phenomena whose models (not only at microscopic and atomic levels) are of difficult, if not impossible, visualization. Just think of certain kinds of waves, fields of forces, velocities, energy, angular momentum, and so on. One should also notice that physical reality is not the same as the images we make of it. Pictures (formal, abstract ones, as well as artists' views) are a convenient bridge between these two aspects.

  14. A quantum-mechanical study of atom-diatom collisions in a laser field

    International Nuclear Information System (INIS)

    Chang, Sintarng.

    1989-01-01

    A quantum-mechanical formalism, in both space-fixed (SF) and body-fixed (BF) coordinate systems, is developed for describing an S-state structureless atom (A) colliding with a Estate vibrating rotor diatomic molecule (BC) in the presence of a laser field. The additional Hamiltonians H rad and H int , which describe the laser field and its interaction with the atom-diatom collision system, have been added to the field-free Hamiltonian Ho. And the collision problem can be solved by this extended Hamiltonian. The laser field Hamiltonian is represented by the number state representation. The interaction Hamiltonian is expressed by rvec μ BC . rvec ε, where rvec μ BC is the dipole moment of the diatomic molecule BC, and rvec ε is the electric field strength of the laser field. Since the field-free total angular momentum J is coupling with the laser field, J and its z-axis projection M are no longer conserved. To facilitate the collision problem, the laser field is restricted to a single mode, and its interaction with the collision only involves dipole allowed transitions in which a single photon is absorbed or emitted. For convenience, the coupled-channel equations are solved by the real boundary conditions instead of the complex boundary conditions. On applying the real boundary conditions, the author obtains the K-matrix, which is related to the S-matrix by S = (I + iK)(I - iK) -1 . A model calculation is discussed for the Ar + CO collision system in a laser intensity of 10 9 W/cm 2

  15. Quantum mechanics of Proca fields

    International Nuclear Information System (INIS)

    Zamani, Farhad; Mostafazadeh, Ali

    2009-01-01

    We construct the most general physically admissible positive-definite inner product on the space of Proca fields. Up to a trivial scaling this defines a five-parameter family of Lorentz invariant inner products that we use to construct a genuine Hilbert space for the quantum mechanics of Proca fields. If we identify the generator of time translations with the Hamiltonian, we obtain a unitary quantum system that describes first-quantized Proca fields and does not involve the conventional restriction to the positive-frequency fields. We provide a rather comprehensive analysis of this system. In particular, we examine the conserved current density responsible for the conservation of the probabilities, explore the global gauge symmetry underlying the conservation of the probabilities, obtain a probability current density, construct position, momentum, helicity, spin, and angular momentum operators, and determine the localized Proca fields. We also compute the generalized parity (P), generalized time-reversal (T), and generalized charge or chirality (C) operators for this system and offer a physical interpretation for its PT-, C-, and CPT-symmetries.

  16. A modern approach to quantum mechanics

    CERN Document Server

    Townsend, John S

    2012-01-01

    Using an innovative approach that students find both accessible and exciting, A Modern Approach to Quantum Mechanics, Second Edition lays out the foundations of quantum mechanics through the physics of intrinsic spin. Written to serve as the primary textbook for an upper-division course in quantum mechanics, Townsend's text gives professors and students a refreshing alternative to the old style of teaching, by allowing the basic physics of spin systems to drive the introduction of concepts such as Dirac notation, operators, eigenstates and eigenvalues, time evolution in quantum mechanics, and entanglement. Chapters 6 through 10 cover the more traditional subjects in wave mechanics-the Schrodinger equation in position space, the harmonic oscillator, orbital angular momentum, and central potentials-but they are motivated by the foundations developed in the earlier chapters. Students using this text will perceive wave mechanics as an important aspect of quantum mechanics, but not necessarily the core of the subj...

  17. Multi-level Quantum Mechanics and Molecular Mechanics Study of Ring Opening Process of Guanine Damage by Hydroxyl Radical in Aqueous Solution.

    Science.gov (United States)

    Liu, Peng; Wang, Qiong; Niu, Meixing; Wang, Dunyou

    2017-08-10

    Combining multi-level quantum mechanics theories and molecular mechanics with an explicit water model, we investigated the ring opening process of guanine damage by hydroxyl radical in aqueous solution. The detailed, atomic-level ring-opening mechanism along the reaction pathway was revealed in aqueous solution at the CCSD(T)/MM levels of theory. The potentials of mean force in aqueous solution were calculated at both the DFT/MM and CCSD(T)/MM levels of the theory. Our study found that the aqueous solution has a significant effect on this reaction in solution. In particular, by comparing the geometries of the stationary points between in gas phase and in aqueous solution, we found that the aqueous solution has a tremendous impact on the torsion angles much more than on the bond lengths and bending angles. Our calculated free-energy barrier height 31.6 kcal/mol at the CCSD(T)/MM level of theory agrees well with the one obtained based on gas-phase reaction profile and free energies of solvation. In addition, the reaction path in gas phase was also mapped using multi-level quantum mechanics theories, which shows a reaction barrier at 19.2 kcal/mol at the CCSD(T) level of theory, agreeing very well with a recent ab initio calculation result at 20.8 kcal/mol.

  18. The geometric semantics of algebraic quantum mechanics.

    Science.gov (United States)

    Cruz Morales, John Alexander; Zilber, Boris

    2015-08-06

    In this paper, we will present an ongoing project that aims to use model theory as a suitable mathematical setting for studying the formalism of quantum mechanics. We argue that this approach provides a geometric semantics for such a formalism by means of establishing a (non-commutative) duality between certain algebraic and geometric objects. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  19. Planar Quantum Mechanics: an Intriguing Supersymmetric Example

    CERN Document Server

    Veneziano, Gabriele

    2006-01-01

    After setting up a Hamiltonian formulation of planar (matrix) quantum mechanics, we illustrate its effectiveness in a non-trivial supersymmetric example. The numerical and analytical study of two sectors of the model, as a function of 't Hooft's coupling $\\lambda$, reveals both a phase transition at $\\lambda=1$ (disappearence of the mass gap and discontinuous jump in Witten's index) and a new form of strong-weak duality for $\\lambda \\to 1/\\lambda$.

  20. Students' Conceptual Difficulties in Quantum Mechanics: Potential Well Problems

    Science.gov (United States)

    Ozcan, Ozgur; Didis, Nilufer; Tasar, Mehmet Fatih

    2009-01-01

    In this study, students' conceptual difficulties about some basic concepts in quantum mechanics like one-dimensional potential well problems and probability density of tunneling particles were identified. For this aim, a multiple choice instrument named Quantum Mechanics Conceptual Test has been developed by one of the researchers of this study…

  1. Level comparison theorems and supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Baumgartner, B.; Grosse, H.

    1986-01-01

    The sign of the Laplacian of the spherical symmetric potential determines the order of energy levels with the same principal Coulomb quantum number. This recently derived theorem has been generalized, extended and applied to various situations in particle, nuclear and atomic physics. Besides a comparison theorem the essential step was the use of supersymmetric quantum mechanics. Recently worked out applications of supersymmetric quantum mechanics to index problems of Dirac operators are mentioned. (Author)

  2. Quantum Mechanical Study of γ-Fe2O3 Nanoparticle as a Nanocarrier for Anticancer Drug Delivery

    Science.gov (United States)

    Lari, Hadi; Morsali, Ali; Heravi, Mohammad Momen

    2018-05-01

    Using density functional theory (DFT), noncovalent interactions and four mechanisms of covalent functionalization of melphalan anticancer drug onto γ-Fe2O3 nanoparticles have been studied. Quantum molecular descriptors of noncovalent configurations were investigated. It was specified that binding of melphalan onto γ-Fe2O3 nanoparticles is thermodynamically suitable. Hardness and the gap of energy between LUMO and HOMO of melphalan are higher than the noncovalent configurations, showing the reactivity of drug increases in the presence of γ-Fe2O3 nanoparticles. Melphalan can bond to γ-Fe2O3 nanoparticles through NH2 (k1 mechanism), OH (k2 mechanism), C=O (k3 mechanism) and Cl (k4 mechanism) groups. The activation energies, the activation enthalpies and the activation Gibbs free energies of these reactions were calculated. Thermodynamic data indicate that k3 mechanism is exothermic and spontaneous and can take place at room temperature. These results could be generalized to other similar drugs.

  3. Elucidating reaction mechanisms on quantum computers

    Science.gov (United States)

    Reiher, Markus; Wiebe, Nathan; Svore, Krysta M.; Wecker, Dave; Troyer, Matthias

    2017-07-01

    With rapid recent advances in quantum technology, we are close to the threshold of quantum devices whose computational powers can exceed those of classical supercomputers. Here, we show that a quantum computer can be used to elucidate reaction mechanisms in complex chemical systems, using the open problem of biological nitrogen fixation in nitrogenase as an example. We discuss how quantum computers can augment classical computer simulations used to probe these reaction mechanisms, to significantly increase their accuracy and enable hitherto intractable simulations. Our resource estimates show that, even when taking into account the substantial overhead of quantum error correction, and the need to compile into discrete gate sets, the necessary computations can be performed in reasonable time on small quantum computers. Our results demonstrate that quantum computers will be able to tackle important problems in chemistry without requiring exorbitant resources.

  4. Elucidating reaction mechanisms on quantum computers

    Science.gov (United States)

    Reiher, Markus; Wiebe, Nathan; Svore, Krysta M.; Wecker, Dave; Troyer, Matthias

    2017-01-01

    With rapid recent advances in quantum technology, we are close to the threshold of quantum devices whose computational powers can exceed those of classical supercomputers. Here, we show that a quantum computer can be used to elucidate reaction mechanisms in complex chemical systems, using the open problem of biological nitrogen fixation in nitrogenase as an example. We discuss how quantum computers can augment classical computer simulations used to probe these reaction mechanisms, to significantly increase their accuracy and enable hitherto intractable simulations. Our resource estimates show that, even when taking into account the substantial overhead of quantum error correction, and the need to compile into discrete gate sets, the necessary computations can be performed in reasonable time on small quantum computers. Our results demonstrate that quantum computers will be able to tackle important problems in chemistry without requiring exorbitant resources. PMID:28674011

  5. Elucidating reaction mechanisms on quantum computers.

    Science.gov (United States)

    Reiher, Markus; Wiebe, Nathan; Svore, Krysta M; Wecker, Dave; Troyer, Matthias

    2017-07-18

    With rapid recent advances in quantum technology, we are close to the threshold of quantum devices whose computational powers can exceed those of classical supercomputers. Here, we show that a quantum computer can be used to elucidate reaction mechanisms in complex chemical systems, using the open problem of biological nitrogen fixation in nitrogenase as an example. We discuss how quantum computers can augment classical computer simulations used to probe these reaction mechanisms, to significantly increase their accuracy and enable hitherto intractable simulations. Our resource estimates show that, even when taking into account the substantial overhead of quantum error correction, and the need to compile into discrete gate sets, the necessary computations can be performed in reasonable time on small quantum computers. Our results demonstrate that quantum computers will be able to tackle important problems in chemistry without requiring exorbitant resources.

  6. The transactional interpretation of quantum mechanics

    Science.gov (United States)

    Cramer, John G.

    2001-06-01

    The transactional interpretation of quantum mechanics [1] was originally published in 1986 and is now about 14 years old. It is an explicitly nonlocal and Lorentz invariant alternative to the Copenhagen interpretation. It interprets the formalism for a quantum interaction as describing a "handshake" between retarded waves (ψ) and advanced waves (ψ*) for each quantum event or "transaction" in which energy, momentum, angular momentum, and other conserved quantities are transferred. The transactional interpretation offers the advantages that (1) it is actually "visible" in the formalism of quantum mechanics, (2) it is economical, involving fewer independent assumptions than its rivals, (3) it is paradox-free, resolving all of the paradoxes of standard quantum theory including nonlocality and wave function collapse, (4) it does not give a privileged role to observers or measurements, and (5) it permits the visualization of quantum events. We will review the transactional interpretation and some of its applications to "quantum paradoxes."

  7. Quantum mechanical study of the proton exchange in the ortho-para H2 conversion reaction at low temperature.

    Science.gov (United States)

    Honvault, P; Jorfi, M; González-Lezana, T; Faure, A; Pagani, L

    2011-11-14

    Ortho-para H(2) conversion reactions mediated by the exchange of a H(+) proton have been investigated at very low energy for the first time by means of a time independent quantum mechanical (TIQM) approach. State-to-state probabilities and cross sections for H(+) + H(2) (v = 0, j = 0,1) processes have been calculated for a collision energy, E(c), ranging between 10(-6) eV and 0.1 eV. Differential cross sections (DCSs) for H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) for very low energies only start to develop a proper global minimum around the sideways scattering direction (θ≈ 90°) at E(c) = 10(-3) eV. Rate coefficients, a crucial information required for astrophysical models, are provided between 10 K and 100 K. The relaxation ortho-para process j = 1 → j' = 0 is found to be more efficient than the j = 0 → j' = 1 conversion at low temperatures, in line with the extremely small ratio between the ortho and para species of molecular hydrogen predicted at the temperature of interstellar cold molecular clouds. The results obtained by means of a statistical quantum mechanical (SQM) model, which has previously proved to provide an adequate description of the dynamics of the title reactions at a higher collision energy regime, have been compared with the TIQM results. A reasonable good agreement has been found with the only exception of the DCSs for the H(+) + H(2) (v = 0, j = 1) → H(+) + H(2) (v' = 0, j' = 0) process at very low energy. SQM cross sections are also slightly below the quantum results. Estimates for the rate coefficients, in good accord with the TIQM values, are a clear improvement with respect to pioneering statistical studies on the reaction.

  8. Analogies between classical statistical mechanics and quantum mechanics

    International Nuclear Information System (INIS)

    Uehara, M.

    1986-01-01

    Some analogies between nonequilibrium classical statistical mechanics and quantum mechanics, at the level of the Liouville equation and at the kinetic level, are commented on. A theorem, related to the Vlasov equation applied to a plasma, is proved. The theorem presents an analogy with Ehrenfest's theorem of quantum mechanics. An analogy between the plasma kinetic theory and Bohm's quantum theory with 'hidden variables' is also shown. (Author) [pt

  9. Quantum Mechanics with a Little Less Mystery

    Science.gov (United States)

    Cropper, William H.

    1969-01-01

    Suggests the "route of the inquiring mind in presenting the esoteric quantum mechanical postulates and concepts in an understandable form. Explains that the quantum mechanical postulates are but useful mathematical forms to express thebroader principles of superposition and correspondence. Briefly describes some of the features which makes the…

  10. Pseudospectra in non-Hermitian quantum mechanics

    Science.gov (United States)

    Krejčiřík, D.; Siegl, P.; Tater, M.; Viola, J.

    2015-10-01

    We propose giving the mathematical concept of the pseudospectrum a central role in quantum mechanics with non-Hermitian operators. We relate pseudospectral properties to quasi-Hermiticity, similarity to self-adjoint operators, and basis properties of eigenfunctions. The abstract results are illustrated by unexpected wild properties of operators familiar from PT -symmetric quantum mechanics.

  11. From quantum mechanics to universal structures of conceptualization and feedback on quantum mechanics

    International Nuclear Information System (INIS)

    Mugur-Schaechter, M.

    1993-01-01

    In previous works we have established that the spacetime probabilistic organization of the quantum theory is determined by the spacetime characteristics of the operations by which the observer produces the objects to be studied (states of microsystems) and obtains qualifications of these. Guided by this first conclusion, we have then built a general syntax of relativized conceptualization where any description is explicity and systematically referred to the two basic epistemic operations by which the conceptor introduces the object to be qualified and then obtains qualifications of it. Inside this syntax there emerges a general typology of the relativized descriptions. Here we show that with respect to this typology the type of the predictive quantum mechanical descriptions acquires a precise definition. It appears that the quantum mechanical formalism has captured and has expressed directly in a mathematical language the most complex form in which can occur a first descriptional phase that lies universally at the bottom of any chain of conceptualization. The main features of the Hilbert-Dirac algorithms are decoded in terms of the general syntax of relativized conceptualiztion. This renders explicit the semantical contents of the quantum mechanical representations relating each one of these to its mathematical quantum mechanical expression. Basic insufficiencies are thus identified and, correlatively, false problems as well as answers to these, or guides towards the answers. Globally the results obtained provide a basis for the future attempts at a general mathematical representation of the processes of conceptualization

  12. Theoretical physics 3. Quantum mechanics 1 with problems in MAPLE

    International Nuclear Information System (INIS)

    Reineker, P.; Schulz, M.; Schulz, B.M.

    2007-01-01

    The following topics are dealt with: Historically heuristic introduction to quantum mechanics, the Schroedinger equation, foundations of quantum mechanics, the linear harmonic oscillator, quantum-mechanical motion in the central field, approximation methods for the solution of quantum mechanical problems, motion of particles in the electromagnetic field, spin and magnetic moment of the electron, many-particle systems, conceptional problems of quantum mechanics

  13. A New Perspective on Relativistic Quantum Mechanics

    International Nuclear Information System (INIS)

    Kong, Otto C W

    2011-01-01

    Based on a linear realization formulation of a quantum relativity, - proposed relativity for 'quantum space-time', we introduce the new Poincare-Snyder relativity and Snyder relativity as relativities in between the latter and the well known Galilean and Einstein cases. While there is supposed to be not separate notion of classical and quantum mechanics at the level of the very unconventional quantum relativity, the Poincare-Snyder relativity is more like a mathematically extended form of Einstein relativity on which we can write down a formal canonical classical and quantum mechanics. We discuss how the Poincare-Snyder relativity may provide a stronger framework for the description of the usual (Einstein) relativistic quantum mechanics and present a first look of the interesting picture from the new perspective.

  14. Polymer quantum mechanics and its continuum limit

    International Nuclear Information System (INIS)

    Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose A.

    2007-01-01

    A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation, has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle, and a simple cosmological model

  15. Mathematical concepts of quantum mechanics. 2. ed.

    International Nuclear Information System (INIS)

    Gustafson, Stephen J.; Sigal, Israel Michael

    2011-01-01

    The book gives a streamlined introduction to quantum mechanics while describing the basic mathematical structures underpinning this discipline. Starting with an overview of key physical experiments illustrating the origin of the physical foundations, the book proceeds with a description of the basic notions of quantum mechanics and their mathematical content. It then makes its way to topics of current interest, specifically those in which mathematics plays an important role. The more advanced topics presented include many-body systems, modern perturbation theory, path integrals, the theory of resonances, quantum statistics, mean-field theory, second quantization, the theory of radiation (non-relativistic quantum electrodynamics), and the renormalization group. With different selections of chapters, the book can serve as a text for an introductory, intermediate, or advanced course in quantum mechanics. The last four chapters could also serve as an introductory course in quantum field theory. (orig.)

  16. Solvable potentials derived from supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Levai, G.

    1994-01-01

    The introduction of supersymmetric quantum mechanics has generated renewed interest in solvable problems of non-relativistic quantum mechanics. This approach offers an elegant way to describe different, but isospectral potentials by interpreting the degeneracy of their energy levels in terms of supersymmetry. The original ideas of supersymmetric quantum mechanics have been developed further in many respects in the past ten years, and have been applied to a large variety of physical problems. The purpose of this contribution is to give a survey of supersymmetric quantum mechanics and its applications to solvable quantum mechanical potentials. Its relation to other models describing isospectral potentials is also discussed here briefly, as well as some of its practical applications in various branches of physics. (orig.)

  17. Does boundary quantum mechanics imply quantum mechanics in the bulk?

    Science.gov (United States)

    Kabat, Daniel; Lifschytz, Gilad

    2018-03-01

    Perturbative bulk reconstruction in AdS/CFT starts by representing a free bulk field ϕ (0) as a smeared operator in the CFT. A series of 1 /N corrections must be added to ϕ (0) to represent an interacting bulk field ϕ. These corrections have been determined in the literature from several points of view. Here we develop a new perspective. We show that correlation functions involving ϕ (0) suffer from ambiguities due to analytic continuation. As a result ϕ (0) fails to be a well-defined linear operator in the CFT. This means bulk reconstruction can be understood as a procedure for building up well-defined operators in the CFT which thereby singles out the interacting field ϕ. We further propose that the difficulty with defining ϕ (0) as a linear operator can be re-interpreted as a breakdown of associativity. Presumably ϕ (0) can only be corrected to become an associative operator in perturbation theory. This suggests that quantum mechanics in the bulk is only valid in perturbation theory around a semiclassical bulk geometry.

  18. Glucose transformation to 5-hydroxymethylfurfural in acidic ionic liquid: A quantum mechanical study.

    Science.gov (United States)

    Arifin; Puripat, Maneeporn; Yokogawa, Daisuke; Parasuk, Vudhichai; Irle, Stephan

    2016-01-30

    Isomerization and transformation of glucose and fructose to 5-hydroxymethylfurfural (HMF) in both ionic liquids (ILs) and water has been studied by the reference interaction site model self-consistent field spatial electron density distribution (RISM-SCF-SEDD) method coupled with ab initio electronic structure theory, namely coupled cluster single, double, and perturbative triple excitation (CCSD(T)). Glucose isomerization to fructose has been investigated via cyclic and open chain mechanisms. In water, the calculations support the cyclic mechanism of glucose isomerization; with the predicted activation free energy is 23.8 kcal mol(-1) at experimental condition. Conversely, open ring mechanism is more favorable in ILs with the energy barrier is 32.4 kcal mol(-1) . Moreover, the transformation of fructose into HMF via cyclic mechanism is reasonable; the calculated activation barriers are 16.0 and 21.5 kcal mol(-1) in aqueous and ILs solutions, respectively. The solvent effects of ILs could be explained by the decomposition of free energies and radial distribution functions of solute-solvent that are produced by RISM-SCF-SEDD. © 2015 Wiley Periodicals, Inc.

  19. Nonlocal quantum field theory and stochastic quantum mechanics

    International Nuclear Information System (INIS)

    Namsrai, K.

    1986-01-01

    This volume presents a systematic development of the implications to both quantum mechanics and quantum field theory of the hypothesis of a stochastic structure of space-time. Some applications to elementary particle physics are also considered. Part 1 is concerned with nonlocal quantum field theory and, among other topics, deals with quantized fields, electromagnetic and weak processes, the Schroedinger equation, and functional methods and their applications. Part 2 presents an introduction to stochastic mechanics and many specific problems of interest are discussed. (Auth.)

  20. Quantum mechanics with non-negative quantum distribution function

    International Nuclear Information System (INIS)

    Zorin, A.V.; Sevastianov, L.A.

    2010-01-01

    Full text: (author)Among numerous approaches to probabilistic interpretation of the conventional quantum mechanics the most close to the N. Bohr idea of the correspondence principle is the D.I. Blokhintzev - Ya.P. Terletsky approach using the quantum distribution function on the coordinate- momentum space. The detailed investigation of this approach has lead to the correspondence rule of V.V. Kuryshkin. Quantum mechanics of Kuryshkin (QMK) embody the program proposed by Yu.M. Shirokov for unifying classical and quantum mechanics in similar mathematical models. QMK develops and enhances Wigner's proposal concerning the calculation of quantum corrections to classical thermodynamic parameters using a phase distribution function. The main result of QMK is the possibility of description by mean of a positively-valued distribution function. This represents an important step towards a completely statistical model of quantum phenomena, compared with the quasi-probabilistic nature of Wigner distribution. Wigner's model does not permit to perform correctly the classical limit in quantum mechanics as well. On the other hand, QMK has a much more complex structure of operators of observables. One of the unsolved problems of QMK is the absence of a priori rules for establishing of auxiliary functions. Nevertheless, while it is impossible to overcome the complex form of operators, we find it quite possible to derive some methods of filing sets of auxiliary functions

  1. Statistical algebraic approach to quantum mechanics

    International Nuclear Information System (INIS)

    Slavnov, D.A.

    2001-01-01

    The scheme for plotting the quantum theory with application of the statistical algebraic approach is proposed. The noncommutative algebra elements (observed ones) and nonlinear functionals on this algebra (physical state) are used as the primary constituents. The latter ones are associated with the single-unit measurement results. Certain physical state groups are proposed to consider as quantum states of the standard quantum mechanics. It is shown that the mathematical apparatus of the standard quantum mechanics may be reproduced in such a scheme in full volume [ru

  2. DNA Damage: Quantum Mechanics/Molecular Mechanics Study on the Oxygen Binding and Substrate Hydroxylation Step in AlkB Repair Enzymes

    Science.gov (United States)

    Quesne, Matthew G; Latifi, Reza; Gonzalez-Ovalle, Luis E; Kumar, Devesh; de Visser, Sam P

    2014-01-01

    AlkB repair enzymes are important nonheme iron enzymes that catalyse the demethylation of alkylated DNA bases in humans, which is a vital reaction in the body that heals externally damaged DNA bases. Its mechanism is currently controversial and in order to resolve the catalytic mechanism of these enzymes, a quantum mechanics/molecular mechanics (QM/MM) study was performed on the demethylation of the N1-methyladenine fragment by AlkB repair enzymes. Firstly, the initial modelling identified the oxygen binding site of the enzyme. Secondly, the oxygen activation mechanism was investigated and a novel pathway was found, whereby the catalytically active iron(IV)–oxo intermediate in the catalytic cycle undergoes an initial isomerisation assisted by an Arg residue in the substrate binding pocket, which then brings the oxo group in close contact with the methyl group of the alkylated DNA base. This enables a subsequent rate-determining hydrogen-atom abstraction on competitive σ-and π-pathways on a quintet spin-state surface. These findings give evidence of different locations of the oxygen and substrate binding channels in the enzyme and the origin of the separation of the oxygen-bound intermediates in the catalytic cycle from substrate. Our studies are compared with small model complexes and the effect of protein and environment on the kinetics and mechanism is explained. PMID:24339041

  3. The relative entropy in the quantum mechanics

    International Nuclear Information System (INIS)

    Lecomte Montes, A.

    1983-06-01

    Relative Entropy is a generalization of entropy which substitutes the Liouville measure from classical mechanics or the trace from quantum mechanics by an arbitrary state. There are many different defintions of it in quantum mechanics because the algebra of observables is not commutative. In this work, three known defintions of the quantum relative entropy are studied and compared but specifically their common properties are presented. The best known defintion was proposed many years ago by Umegaki and later on by Lindblad. This defintion can be realized through a functional calculus for quadratic forms introduced by Pusz and Woronowicz, for two arbitrary states on a Csup(*)-algebra. The two other definitions investigated are the Naudt's entropy and the inference function of Marchand and Wyss. The first one can be expressed through the functional calculus too, it has then almost the same properties as the Umegaki-Lindblad defintion. The inference function can be considered only as some kind of 1/2-relative entropy. The function is nevertheless very important because it can be expressed as the logarithm of the transition probability between the basis state and the actual state. A general theory which includes the three defintions is not found yet, but it is shown that the functional calculus provides a great family of relative entropies. This is important for a unified theory of all defintions and their properties. (Author)

  4. Supersymmetric quantum mechanics under point singularities

    International Nuclear Information System (INIS)

    Uchino, Takashi; Tsutsui, Izumi

    2003-01-01

    We provide a systematic study on the possibility of supersymmetry (SUSY) for one-dimensional quantum mechanical systems consisting of a pair of lines R or intervals [-l, l] each having a point singularity. We consider the most general singularities and walls (boundaries) at x = ±l admitted quantum mechanically, using a U(2) family of parameters to specify one singularity and similarly a U(1) family of parameters to specify one wall. With these parameter freedoms, we find that for a certain subfamily the line systems acquire an N = 1 SUSY which can be enhanced to N = 4 if the parameters are further tuned, and that these SUSY are generically broken except for a special case. The interval systems, on the other hand, can accommodate N = 2 or N = 4 SUSY, broken or unbroken, and exhibit a rich variety of (degenerate) spectra. Our SUSY systems include the familiar SUSY systems with the Dirac δ(x)-potential, and hence are extensions of the known SUSY quantum mechanics to those with general point singularities and walls. The self-adjointness of the supercharge in relation to the self-adjointness of the Hamiltonian is also discussed

  5. Quantum mechanical metastability: When and why?

    International Nuclear Information System (INIS)

    Boyanovsky, D.; Willey, R.; Holman, R.

    1992-01-01

    We study quantum mechanical metastability with an eye towards false vacuum decay. We point out some technical and conceptual problems with the familiar bounce treatment of this process. We illustrate with simple quantum mechanical examples that the bounce formalism fails to account for the correct boundary conditions. It is also shown, that the bounce approach overestimates the time scales for tunneling of localized packets in typical (slightly) biased double well potentials. We present a thorough WKB analysis with particular attention to semiclassical trajectories corresponding to complex saddle points. We point out that the boundary conditions determine the proper choice of saddle points and the bounce approach fails to account for semiclassical trajectories in many physically relevant cases. We recognize that these saddle points account for the matching conditions of the WKB wave functions beyond the barriers and restore unitarity and reality of eigenvalues for self-adjoint boundary conditions. We provide a novel approach to the semiclassical analysis of out of equilibrium decay in real time in quantum statistical mechanics. (orig.)

  6. Density operators in quantum mechanics

    International Nuclear Information System (INIS)

    Burzynski, A.

    1979-01-01

    A brief discussion and resume of density operator formalism in the way it occurs in modern physics (in quantum optics, quantum statistical physics, quantum theory of radiation) is presented. Particularly we emphasize the projection operator method, application of spectral theorems and superoperators formalism in operator Hilbert spaces (Hilbert-Schmidt type). The paper includes an appendix on direct sums and direct products of spaces and operators, and problems of reducibility for operator class by using the projection operators. (author)

  7. Quantum KAM technique and Yang endash Mills quantum mechanics

    International Nuclear Information System (INIS)

    Halperin, I.

    1995-01-01

    We study a quantum analogue of the iterative perturbation theory by Kolmogorov used in the proof of the Kolmogorov endash Arnold endash Moser (KAM) theorem. The method is based on sequent canonical transformations with a open-quote open-quote running close-quote close-quote coupling constant λ, λ 2 , λ 4 , etc. The proposed scheme, as its classical predecessor, is open-quote open-quote superconvergent close-quote close-quote in the sense that after the nth step, a theory is solved to the accuracy of order λ 2n-1 . It is shown that the Kolmogorov technique corresponds to an infinite resummation of the usual perturbative series. The corresponding expansion is convergent for the quantum anharmonic oscillator due to the fact that it turns out to be identical to the Pade series. The method is easily generalizable to many-dimensional cases. The Kolmogorov technique is further applied to a non-perturbative treatment of Yang endash Mills quantum mechanics. A controllable expansion for the wave function near the origin is constructed. For large fields, we build an asymptotic adiabatic expansion in inverse powers of the field. This asymptotic solution contains arbitrary constants which are not fixed by the boundary conditions at infinity. To find them, we approximately match the two expansions in an intermediate region. We also discuss some analogies between this problem and the method of QCD sum rules. Copyright copyright 1995 Academic Press, Inc

  8. Randomness and locality in quantum mechanics

    International Nuclear Information System (INIS)

    Bub, J.

    1976-01-01

    This paper considers the problem of representing the statistical states of a quantum mechanical system by measures on a classical probability space. The Kochen and Specker theorem proves the impossibility of embedding the possibility structure of a quantum mechanical system into a Boolean algebra. It is shown that a hidden variable theory involves a Boolean representation which is not an embedding, and that such a representation cannot recover the quantum statistics for sequential probabilities without introducing a randomization process for the hidden variables which is assumed to apply only on measurement. It is suggested that the relation of incompatability is to be understood as a type of stochastic independence, and that the indeterminism of a quantum mechanical system is engendered by the existence of independent families of properties. Thus, the statistical relations reflect the possibility structure of the system: the probabilities are logical. The hidden variable thesis is influenced by the Copenhagen interpretation of quantum mechanics, i.e. by some version of the disturbance theory of measurement. Hence, the significance of the representation problem is missed, and the completeness of quantum mechanics is seen to turn on the possibility of recovering the quantum statistics by a hidden variable scheme which satisfies certain physically motivated conditions, such as locality. Bell's proof that no local hidden variable theory can reproduce the statistical relations of quantum mechanics is considered. (Auth.)

  9. Quantum mechanics a comprehensive text for chemistry

    CERN Document Server

    Arora, Kishor

    2010-01-01

    This book contains 14 chapters. The text includes the inadequacy of classical mechanics and covers basic and fundamental concepts of quantum mechanics including concepts of transitional, vibration rotation and electronic energies, introduction to concepts of angular momenta, approximatemethods and their application concepts related to electron spin, symmetery concepts and quantum mechanics and ultimately the book features the theories of chemical bonding and use of softwares in quantum mechanics. the text of the book is presented in a lucid manner with ample examples and illustrations wherever

  10. Recent trials to verify quantum mechanics

    International Nuclear Information System (INIS)

    Paty, M.

    1974-01-01

    An account of the experiments which deal with the verification of Quantum Mechanics and the hidden variable problem is made. First, the well-known EPR paradox is recalled which, in spite of its refutation by Bohr, was the starting point of the questionning on the completeness of Quantum Mechanics and of hidden variable theories; and then Bell's theorem, which shows that the two approaches, Quantum Mechanics and hidden variables, can be put in contradiction. Thereafter the various types of experiments which have been carried out on that subject, mostly concerning the correlation measurements between two photons emitted by a quantum system are described. The most recent experimental results are diverging, some of them to confirm and some others to contradict quantum mechanics. A review of these is given; and a discussion is presented about their possible implications [fr

  11. Emergence of classical theories from quantum mechanics

    International Nuclear Information System (INIS)

    Hájícek, P

    2012-01-01

    Three problems stand in the way of deriving classical theories from quantum mechanics: those of realist interpretation, of classical properties and of quantum measurement. Recently, we have identified some tacit assumptions that lie at the roots of these problems. Thus, a realist interpretation is hindered by the assumption that the only properties of quantum systems are values of observables. If one simply postulates the properties to be objective that are uniquely defined by preparation then all difficulties disappear. As for classical properties, the wrong assumption is that there are arbitrarily sharp classical trajectories. It turns out that fuzzy classical trajectories can be obtained from quantum mechanics by taking the limit of high entropy. Finally, standard quantum mechanics implies that any registration on a quantum system is disturbed by all quantum systems of the same kind existing somewhere in the universe. If one works out systematically how quantum mechanics must be corrected so that there is no such disturbance, one finds a new interpretation of von Neumann's 'first kind of dynamics', and so a new way to a solution of the quantum measurement problem. The present paper gives a very short review of this work.

  12. Emergence of quantum mechanics from classical statistics

    International Nuclear Information System (INIS)

    Wetterich, C

    2009-01-01

    The conceptual setting of quantum mechanics is subject to an ongoing debate from its beginnings until now. The consequences of the apparent differences between quantum statistics and classical statistics range from the philosophical interpretations to practical issues as quantum computing. In this note we demonstrate how quantum mechanics can emerge from classical statistical systems. We discuss conditions and circumstances for this to happen. Quantum systems describe isolated subsystems of classical statistical systems with infinitely many states. While infinitely many classical observables 'measure' properties of the subsystem and its environment, the state of the subsystem can be characterized by the expectation values of only a few probabilistic observables. They define a density matrix, and all the usual laws of quantum mechanics follow. No concepts beyond classical statistics are needed for quantum physics - the differences are only apparent and result from the particularities of those classical statistical systems which admit a quantum mechanical description. In particular, we show how the non-commuting properties of quantum operators are associated to the use of conditional probabilities within the classical system, and how a unitary time evolution reflects the isolation of the subsystem.

  13. Quantum mechanical study of molecular collisions at ultra-low energy: applications to alkali and alkaline-earth systems

    International Nuclear Information System (INIS)

    Quemener, G.

    2006-10-01

    In order to investigate the collisional processes which occur during the formation of molecular Bose-Einstein condensates, a time-independent quantum mechanical formalism, based on hyperspherical coordinates, has been applied to the study of atom-diatom dynamics at ultra-low energies. We present theoretical results for three alkali systems, each composed of lithium, sodium or potassium atoms, and for an alkaline-earth system composed of calcium atoms. We also study dynamics at large and positive atom-atom scattering length. Evidence for the suppression of inelastic processes in a fermionic system is given, as well as a linear relation between the atom-diatom scattering length and the atom-atom scattering length. (author)

  14. Prologue to super quantum mechanics something is rotten in the state of quantum mechanics

    CERN Document Server

    Vaguine, Victor

    2012-01-01

    Since its foundation more than eight decades ago, quantum mechanics has been plagued by enigmas, mysteries and paradoxes and held hostage by quantum positivism. This fact strongly suggests that something is fundamentally wrong with the quantum mechanics paradigm. The best scientific minds, such as Albert Einstein, Louis de Broglie, David Bohm, Richard Feynman and others have spent years of their professional lives attempting to find resolution to the quantum mechanics predicament, with not much success. A shift of the quantum mechanics paradigm toward a deeper physics theory is long overdue.

  15. Classical- and quantum mechanical Coulomb scattering

    International Nuclear Information System (INIS)

    Gratzl, W.

    1987-01-01

    Because in textbooks the quantum mechanical Coulomb scattering is either ignored or treated unsatisfactory, the present work attempts to present a physically plausible, mathematically correct but elementary treatment in a way that it can be used in textbooks and lectures on quantum mechanics. Coulomb scattering is derived as a limiting case of a screened Coulomb potential (finite range) within a time dependent quantum scattering theory. The difference in the asymptotic conditions for potentials of finite versus infinite range leads back to the classical Coulomb scattering. In the classical framework many concepts of the quantum theory can be introduced and are useful in an intuitive understanding of the quantum theory. The differences between classical and quantum scattering theory are likewise useful for didactic purposes. (qui)

  16. A multi-level quantum mechanics and molecular mechanics study of SN2 reaction at nitrogen: NH2Cl + OH(-) in aqueous solution.

    Science.gov (United States)

    Lv, Jing; Zhang, Jingxue; Wang, Dunyou

    2016-02-17

    We employed a multi-level quantum mechanics and molecular mechanics approach to study the reaction NH2Cl + OH(-) in aqueous solution. The multi-level quantum method (including the DFT method with both the B3LYP and M06-2X exchange-correlation functionals and the CCSD(T) method, and both methods with the aug-cc-pVDZ basis set) was used to treat the quantum reaction region in different stages of the calculation in order to obtain an accurate potential of mean force. The obtained free energy activation barriers at the DFT/MM level of theory yielded a big difference of 21.8 kcal mol(-1) with the B3LYP functional and 27.4 kcal mol(-1) with the M06-2X functional respectively. Nonetheless, the barrier heights become very close when shifted from DFT to CCSD(T): 22.4 kcal mol(-1) and 22.9 kcal mol(-1) at CCSD(T)(B3LYP)/MM and CCSD(T)(M06-2X)/MM levels of theory, respectively. The free reaction energy obtained using CCSD(T)(M06-2X)/MM shows an excellent agreement with the one calculated using the available gas-phase data. Aqueous solution plays a significant role in shaping the reaction profile. In total, the water solution contributes 13.3 kcal mol(-1) and 14.6 kcal mol(-1) to the free energy barrier heights at CCSD(T)(B3LYP)/MM and CCSD(T)(M06-2X)/MM respectively. The title reaction at nitrogen is a faster reaction than the corresponding reaction at carbon, CH3Cl + OH(-).

  17. On the Completeness of Quantum Mechanics

    OpenAIRE

    Kupczynski, Marian

    2002-01-01

    Quantum cryptography, quantum computer project, space-time quantization program and recent computer experiments reported by Accardi and his collaborators show the importance and actuality of the discussion of the completeness of quantum mechanics (QM) started by Einstein more than 70 years ago. Many years ago we pointed out that the violation of Bell's inequalities is neither a proof of completeness of QM nor an indication of the violation of Einsteinian causality. We also indicated how and i...

  18. Topological strings from quantum mechanics

    International Nuclear Information System (INIS)

    Grassi, Alba; Marino, Marcos; Hatsuda, Yasuyuki

    2014-12-01

    We propose a general correspondence which associates a non-perturbative quantum-mechanical operator to a toric Calabi-Yau manifold, and we conjecture an explicit formula for its spectral determinant in terms of an M-theoretic version of the topological string free energy. As a consequence, we derive an exact quantization condition for the operator spectrum, in terms of the vanishing of a generalized θ function. The perturbative part of this quantization condition is given by the Nekrasov-Shatashvili limit of the refined topological string, but there are non-perturbative corrections determined by the conventional topological string. We analyze in detail the cases of local P 2 , local P 1 x P 1 and local F 1 . In all these cases, the predictions for the spectrum agree with the existing numerical results. We also show explicitly that our conjectured spectral determinant leads to the correct spectral traces of the corresponding operators, which are closely related to topological string theory at orbifold points. Physically, our results provide a Fermi gas picture of topological strings on toric Calabi-Yau manifolds, which is fully non-perturbative and background independent. They also suggest the existence of an underlying theory of M2 branes behind this formulation. Mathematically, our results lead to precise, surprising conjectures relating the spectral theory of functional difference operators to enumerative geometry.

  19. A reinterpretation of quantum mechanics

    International Nuclear Information System (INIS)

    Anastasov, A.H.

    1983-01-01

    A solution of the problem of corpuscular-wave dualism is proposed. It consists in the establishment of a continual-discrete, stochastic-deterministic space-time model of the 'particle in a quantum-mechanical sense'. This solution differs radically from the so-called Copenhagen interpretation. It has points of contact with de Broglie's double solution as well as with the fluid models, but avoids their shortcomings. The main shortcoming of the double solution is that it retains the particle's trajectory while in the fluid models there is no trace dicreteness. Moreover, when two or more interacting particles are involved, the wave function and the corresponding fluid both lose their physical reality, being defined in a configurational rather than in a real physical space. The corpuscular-wave object described here is called POLLETRON. Mathematically this is a pair of geometric objects in the space-time of the relativity theory. At the partial expense of depth and naturalness, a poletron can also be described classically, although its behaviour runs counter to the classical rules. This non-relativistic description based on the notion of a QUANTON is given here. A QUANTON is a classical particle (material point) which, however, is supershortliving (a 'particle-phantom')

  20. Bell's inequalities for quantum mechanics

    International Nuclear Information System (INIS)

    Andaas, H.E.

    1991-10-01

    Inequalities corresponding to the generalized Bell's inequalities of local realism are derived for the quantum case. The extremal values permitted by these inequalities exceed those allowed by the generalized Bell's inequalities. Quantum predictions for systems of two spin-1/2 particles prepared as mixtures do not violate Bell's inequalities. 15 refs

  1. Three-dimensional quantum mechanical studies of D+H2 → HD+H reactive scattering

    International Nuclear Information System (INIS)

    Tang, K.T.; Choi, B.H.

    1975-01-01

    A three-dimensional quantum mechanical study is made on the reactive scattering of D+H 2 → DH+H. The differential and total cross sections as well as the S-matrix elements are obtained from the adiabatic distorted wave model. With the initial molecule H 2 in the ground rotational state, we calculated the cross sections for reactions to all possible rotational states of the product molecule DH. The potential used is that of the Porter and Karplus semiempirical surface. The reactive scattering is predominantly backward. However, the peak in the differential cross sections gradually shifts away from theta=π as the energy is increased, with higher rotational states shifting more. In the thermal energy region, there is virtually no scattering in forward directions. The reaction is endothermic but only slightly so. Although the 0→0 rotational transition contributes only a small fraction to the total reactive cross section, most product molecules prefer rotational states that are considerably lower than the highest one allowed by energy conservation. Differential cross sections summed over all possible final rotational states are significantly different from that of any one state. Previous three-dimensional quantum mechanical studies on this system are all limited to one final rotational state; these previous results are compared with the result of the corresponding case in the present study. The present results are also compared with the corresponding classical trajectory calculations on the same potential surface. Finally, the experimental measurements of Geddes, Kraus, and Fite are compared with the present results. Qualitatively, there are general agreements. but quantitatively the calculated cross sections are definitely too large as compared with the experimental ones. The most likely cause for this difference is that the potential surface used is ''too reactive.''

  2. The equivalence principle in classical mechanics and quantum mechanics

    OpenAIRE

    Mannheim, Philip D.

    1998-01-01

    We discuss our understanding of the equivalence principle in both classical mechanics and quantum mechanics. We show that not only does the equivalence principle hold for the trajectories of quantum particles in a background gravitational field, but also that it is only because of this that the equivalence principle is even to be expected to hold for classical particles at all.

  3. The relation between classical and quantum mechanics

    International Nuclear Information System (INIS)

    Taylor, Peter.

    1984-01-01

    The thesis examines the relationship between classical and quantum mechanics from philosophical, mathematical and physical standpoints. Arguments are presented in favour of 'conjectural realism' in scientific theories, distinguished by explicit contextual structure and empirical testability. The formulations of classical and quantum mechanics, based on a general theory of mechanics is investigated, as well as the mathematical treatments of these subjects. Finally the thesis questions the validity of 'classical limits' and 'quantisations' in intertheoretic reduction. (UK)

  4. Multi-level quantum mechanics theories and molecular mechanics study of the double-inversion mechanism of the F- + CH3I reaction in aqueous solution.

    Science.gov (United States)

    Liu, Peng; Zhang, Jingxue; Wang, Dunyou

    2017-06-07

    A double-inversion mechanism of the F - + CH 3 I reaction was discovered in aqueous solution using combined multi-level quantum mechanics theories and molecular mechanics. The stationary points along the reaction path show very different structures to the ones in the gas phase due to the interactions between the solvent and solute, especially strong hydrogen bonds. An intermediate complex, a minimum on the potential of mean force, was found to serve as a connecting-link between the abstraction-induced inversion transition state and the Walden-inversion transition state. The potentials of mean force were calculated with both the DFT/MM and CCSD(T)/MM levels of theory. Our calculated free energy barrier of the abstraction-induced inversion is 69.5 kcal mol -1 at the CCSD(T)/MM level of theory, which agrees with the one at 72.9 kcal mol -1 calculated using the Born solvation model and gas-phase data; and our calculated free energy barrier of the Walden inversion is 24.2 kcal mol -1 , which agrees very well with the experimental value at 25.2 kcal mol -1 in aqueous solution. The calculations show that the aqueous solution makes significant contributions to the potentials of mean force and exerts a big impact on the molecular-level evolution along the reaction pathway.

  5. Development and validation of an achievement test in introductory quantum mechanics: The Quantum Mechanics Visualization Instrument (QMVI)

    Science.gov (United States)

    Cataloglu, Erdat

    The purpose of this study was to construct a valid and reliable multiple-choice achievement test to assess students' understanding of core concepts of introductory quantum mechanics. Development of the Quantum Mechanics Visualization Instrument (QMVI) occurred across four successive semesters in 1999--2001. During this time 213 undergraduate and graduate students attending the Pennsylvania State University (PSU) at University Park and Arizona State University (ASU) participated in this development and validation study. Participating students were enrolled in four distinct groups of courses: Modern Physics, Undergraduate Quantum Mechanics, Graduate Quantum Mechanics, and Chemistry Quantum Mechanics. Expert panels of professors of physics experienced in teaching quantum mechanics courses and graduate students in physics and science education established the core content and assisted in the validating of successive versions of the 24-question QMVI. Instrument development was guided by procedures outlined in the Standards for Educational and Psychological Testing (AERA-APA-NCME, 1999). Data gathered in this study provided information used in the development of successive versions of the QMVI. Data gathered in the final phase of administration of the QMVI also provided evidence that the intended score interpretation of the QMVI achievement test is valid and reliable. A moderate positive correlation coefficient of 0.49 was observed between the students' QMVI scores and their confidence levels. Analyses of variance indicated that students' scores in Graduate Quantum Mechanics and Undergraduate Quantum Mechanics courses were significantly higher than the mean scores of students in Modern Physics and Chemistry Quantum Mechanics courses (p important factor for students in acquiring a successful understanding of quantum mechanics.

  6. Investigations on quantum mechanics with minimal length

    International Nuclear Information System (INIS)

    Chargui, Yassine

    2009-01-01

    We consider a modified quantum mechanics where the coordinates and momenta are assumed to satisfy a non-standard commutation relation of the form( X i , P j ) = iℎ(δ ij (1+βP 2 )+β'P i P j ). Such an algebra results in a generalized uncertainty relation which leads to the existence of a minimal observable length. Moreover, it incorporates an UV/IR mixing and non commutative position space. We analyse the possible representations in terms of differential operators. The latter are used to study the low energy effects of the minimal length by considering different quantum systems : the harmonic oscillator, the Klein-Gordon oscillator, the spinless Salpeter Coulomb problem, and the Dirac equation with a linear confining potential. We also discuss whether such effects are observable in precision measurements on a relativistic electron trapped in strong magnetic field.

  7. Uncertainty and Complementarity in Axiomatic Quantum Mechanics

    Science.gov (United States)

    Lahti, Pekka J.

    1980-11-01

    In this work an investigation of the uncertainty principle and the complementarity principle is carried through. A study of the physical content of these principles and their representation in the conventional Hilbert space formulation of quantum mechanics forms a natural starting point for this analysis. Thereafter is presented more general axiomatic framework for quantum mechanics, namely, a probability function formulation of the theory. In this general framework two extra axioms are stated, reflecting the ideas of the uncertainty principle and the complementarity principle, respectively. The quantal features of these axioms are explicated. The sufficiency of the state system guarantees that the observables satisfying the uncertainty principle are unbounded and noncompatible. The complementarity principle implies a non-Boolean proposition structure for the theory. Moreover, nonconstant complementary observables are always noncompatible. The uncertainty principle and the complementarity principle, as formulated in this work, are mutually independent. Some order is thus brought into the confused discussion about the interrelations of these two important principles. A comparison of the present formulations of the uncertainty principle and the complementarity principle with the Jauch formulation of the superposition principle is also given. The mutual independence of the three fundamental principles of the quantum theory is hereby revealed.

  8. Optimization of a relativistic quantum mechanical engine.

    Science.gov (United States)

    Peña, Francisco J; Ferré, Michel; Orellana, P A; Rojas, René G; Vargas, P

    2016-08-01

    We present an optimal analysis for a quantum mechanical engine working between two energy baths within the framework of relativistic quantum mechanics, adopting a first-order correction. This quantum mechanical engine, with the direct energy leakage between the energy baths, consists of two adiabatic and two isoenergetic processes and uses a three-level system of two noninteracting fermions as its working substance. Assuming that the potential wall moves at a finite speed, we derive the expression of power output and, in particular, reproduce the expression for the efficiency at maximum power.

  9. Quantum-mechanical computers and uncomputability

    International Nuclear Information System (INIS)

    Lloyd, S.

    1993-01-01

    The time evolution operator for any quantum-mechanical computer is diagonalizable, but to obtain the diagonal decomposition of a program state of the computer is as hard as actually performing the computation corresponding to the program. In particular, if a quantum-mechanical system is capable of universal computation, then the diagonal decomposition of program states is uncomputable. As a result, in a universe in which local variables support universal computation, a quantum-mechanical theory for that universe that supplies its spectrum cannot supply the spectral decomposition of the computational variables. A ''theory of everything'' can be simultaneously correct and fundamentally incomplete

  10. Quantum mechanics as total physical theory

    International Nuclear Information System (INIS)

    Slavnov, D.A.

    2002-01-01

    It is shown that the principles of the total physical theory and conclusions of the standard quantum mechanics are not at such an antagonistic variance as it is usually accepted. The axioms, which make it possible to plot the renewed mathematical scheme of the quantum mechanics are formulated within the frames of the algebraic approach. The above scheme includes the standard mathematical apparatus of the quantum mechanics. Simultaneously there exists the mathematical object, which adequately describes the individual experiment. The examples of applying the proposed scheme is presented [ru

  11. Theoretical and quantum mechanics fundamentals for chemists

    CERN Document Server

    Ivanov, Stefan

    2006-01-01

    Provides the basics of theoretical and quantum mechanics in one place and emphasizes the continuity between themUniquely presented to be used for self-taught courses covering theoretical and quantum mechanicsEach chapter includes a detailed outline, a summary, self-assessment questions for which answers can be found in the textInvaluable for chemistry undergraduate and graduate students, chemists, other non-physical scientists, engineering students of modern techniques and technology, specialists who need a better understanding of quantum mechanics.

  12. Quantum Chemical Study on the Antioxidation Mechanism of Piceatannol and Isorhapontigenin toward Hydroxyl and Hydroperoxyl Radicals.

    Directory of Open Access Journals (Sweden)

    Yang Lu

    Full Text Available A systematic study of the antioxidation mechanisms behind hydroxyl (•OH and hydroperoxyl (•OOH radical scavenging activity of piceatannol (PIC and isorhapontigenin (ISO was carried out using density functional theory (DFT method. Two reaction mechanisms, abstraction (ABS and radical adduct formation (RAF, were discussed. A total of 24 reaction pathways of scavenging •OH and •OOH with PIC and ISO were investigated in the gas phase and solution. The thermodynamic and kinetic properties of all pathways were calculated. Based on these results, we evaluated the antioxidant activity of every active site of PIC and ISO and compared the abilities of PIC and ISO to scavenge radicals. According to our results, PIC and ISO may act as effective •OH and •OOH scavengers in organism. A4-hydroxyl group is a very important active site for PIC and ISO to scavenge radicals. The introducing of -OH or -OCH3 group to the ortho-position of A4-hydroxyl group would increase its antioxidant activity. Meanwhile, the conformational effect was researched, the results suggest that the presence and pattern of intramolecular hydrogen bond (IHB are considerable in determining the antioxidant activity of PIC and ISO.

  13. Relativistic quantum mechanics; Mecanique quantique relativiste

    Energy Technology Data Exchange (ETDEWEB)

    Ollitrault, J.Y. [CEA Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique]|[Universite Pierre et Marie Curie, 75 - Paris (France)

    1998-12-01

    These notes form an introduction to relativistic quantum mechanics. The mathematical formalism has been reduced to the minimum in order to enable the reader to calculate elementary physical processes. The second quantification and the field theory are the logical followings of this course. The reader is expected to know analytical mechanics (Lagrangian and Hamiltonian), non-relativistic quantum mechanics and some basis of restricted relativity. The purpose of the first 3 chapters is to define the quantum mechanics framework for already known notions about rotation transformations, wave propagation and restricted theory of relativity. The next 3 chapters are devoted to the application of relativistic quantum mechanics to a particle with 0,1/5 and 1 spin value. The last chapter deals with the processes involving several particles, these processes require field theory framework to be thoroughly described. (A.C.) 2 refs.

  14. Quantum mechanics in simple matrix form

    CERN Document Server

    Jordan, Thomas F

    1986-01-01

    With this text, basic quantum mechanics becomes accessible to undergraduates with no background in mathematics beyond algebra. Containing more than 100 problems, it provides an easy way to learn part of the quantum language and to employ this new skill in solving problems.

  15. Problems in Quantum Mechanics with Solutions

    CERN Document Server

    d'Emilio, Emilio

    2011-01-01

    242 solved problems of several degrees of difficulty in nonrelativistic Quantum Mechanics, ranging from the themes of the crisis of classical physics, through the achievements in the framework of modern atomic physics, down to the still alive, more intriguing aspects connected e.g. with the EPR paradox, the Aharonov--Bohm effect, quantum teleportation.

  16. The reality problem in quantum mechanics

    International Nuclear Information System (INIS)

    Flamm, D.

    1988-01-01

    A series of 12 lectures on quantum mechanics and its inter-pretations: The more specific part begins with chapter 8: spin and polarization measurements; the Einstein-Podolski-Rosen paradoxon; Bell's inequations; interpretations of quantum theory; the role of the observer and the wave function of the world. 40 refs., 11 figs. (qui)

  17. Quantum mechanics: why complex Hilbert space?

    Science.gov (United States)

    Cassinelli, G.; Lahti, P.

    2017-10-01

    We outline a programme for an axiomatic reconstruction of quantum mechanics based on the statistical duality of states and effects that combines the use of a theorem of Solér with the idea of symmetry. We also discuss arguments favouring the choice of the complex field. This article is part of the themed issue `Second quantum revolution: foundational questions'.

  18. A study of quantum mechanical probabilities in the classical Hodgkin-Huxley model.

    Science.gov (United States)

    Moradi, N; Scholkmann, F; Salari, V

    2015-03-01

    The Hodgkin-Huxley (HH) model is a powerful model to explain different aspects of spike generation in excitable cells. However, the HH model was proposed in 1952 when the real structure of the ion channel was unknown. It is now common knowledge that in many ion-channel proteins the flow of ions through the pore is governed by a gate, comprising a so-called "selectivity filter" inside the ion channel, which can be controlled by electrical interactions. The selectivity filter (SF) is believed to be responsible for the selection and fast conduction of particular ions across the membrane of an excitable cell. Other (generally larger) parts of the molecule such as the pore-domain gate control the access of ions to the channel protein. In fact, two types of gates are considered here for ion channels: the "external gate", which is the voltage sensitive gate, and the "internal gate" which is the selectivity filter gate (SFG). Some quantum effects are expected in the SFG due to its small dimensions, which may play an important role in the operation of an ion channel. Here, we examine parameters in a generalized model of HH to see whether any parameter affects the spike generation. Our results indicate that the previously suggested semi-quantum-classical equation proposed by Bernroider and Summhammer (BS) agrees strongly with the HH equation under different conditions and may even provide a better explanation in some cases. We conclude that the BS model can refine the classical HH model substantially.

  19. A QUANTUM MECHANICAL STUDY OF THE PROTONATION AND COVALENT HYDRATION OF QUINAZOLINE IN THE PRESENCE OF METAL CATIONS

    Science.gov (United States)

    We have investigated the protonation and reversible covalent hydration of quinazoline in the presence of Li+, Na+, and Ca2+ ions using ab initio quantum mechanical calculations at the MP2/6-31G**//HF/6-31G*level of theory. Proton affinities, enthalpies of hydration at 298.15K (DH...

  20. Cartoon computation: quantum-like computing without quantum mechanics

    International Nuclear Information System (INIS)

    Aerts, Diederik; Czachor, Marek

    2007-01-01

    We present a computational framework based on geometric structures. No quantum mechanics is involved, and yet the algorithms perform tasks analogous to quantum computation. Tensor products and entangled states are not needed-they are replaced by sets of basic shapes. To test the formalism we solve in geometric terms the Deutsch-Jozsa problem, historically the first example that demonstrated the potential power of quantum computation. Each step of the algorithm has a clear geometric interpretation and allows for a cartoon representation. (fast track communication)

  1. The mechanism of suppression of quantum transitions (quantum whirligig)

    International Nuclear Information System (INIS)

    Buts, V.A.

    2010-01-01

    The mechanism allowing to stabilize of a state of quantum systems is considered. And, the initial condition can correspond both for excited state and for not excited, stationary state. The considered mechanism for the first time was offered for the excited states, and has received the name as quantum whirligig (QWE). In this work the close connection of the considered mechanism with Zeno effect is shown. The considerations are stated, that many experimental results, which are interpreted as observation of Zeno effect, apparently, correspond to QWE.

  2. Quantum mechanics with applications to quarkonium

    International Nuclear Information System (INIS)

    Quigg, C.; Rosner, J.L.

    1979-02-01

    Some methods of nonrelativistic quantum mechanics which are particularly useful for studying the variation of bound-state parameters with constituent mass and excitation energy are reviewed. These techniques rely upon elementary scaling arguments and on the semiclassical (WKB) approximation. They are of general interest, but are applied here to the study of bound systems of a heavy quark and antiquark. Properties of the interquark interaction are extracted from information about masses and leptonic widths of the Psi and T families. It is shown how general methods can be applied to the determination of the electric charge of quarks and to the prediction of properties of new families. 113 references

  3. Black holes and quantum mechanics

    CERN Document Server

    Wilczek, Frank

    1995-01-01

    1. Qualitative introduction to black holes : classical, quantum2. Model black holes and model collapse process: The Schwarzschild and Reissner-Nordstrom metrics, The Oppenheimer-Volkov collapse scenario3. Mode mixing4. From mode mixing to radiance.

  4. Review of student difficulties in upper-level quantum mechanics

    Directory of Open Access Journals (Sweden)

    Chandralekha Singh

    2015-09-01

    Full Text Available [This paper is part of the Focused Collection on Upper Division Physics Courses.] Learning advanced physics, in general, is challenging not only due to the increased mathematical sophistication but also because one must continue to build on all of the prior knowledge acquired at the introductory and intermediate levels. In addition, learning quantum mechanics can be especially challenging because the paradigms of classical mechanics and quantum mechanics are very different. Here, we review research on student reasoning difficulties in learning upper-level quantum mechanics and research on students’ problem-solving and metacognitive skills in these courses. Some of these studies were multiuniversity investigations. The investigations suggest that there is large diversity in student performance in upper-level quantum mechanics regardless of the university, textbook, or instructor, and many students in these courses have not acquired a functional understanding of the fundamental concepts. The nature of reasoning difficulties in learning quantum mechanics is analogous to reasoning difficulties found via research in introductory physics courses. The reasoning difficulties were often due to overgeneralizations of concepts learned in one context to another context where they are not directly applicable. Reasoning difficulties in distinguishing between closely related concepts and in making sense of the formalism of quantum mechanics were common. We conclude with a brief summary of the research-based approaches that take advantage of research on student difficulties in order to improve teaching and learning of quantum mechanics.

  5. Quantum mechanics and the equivalence principle

    International Nuclear Information System (INIS)

    Davies, P C W

    2004-01-01

    A quantum particle moving in a gravitational field may penetrate the classically forbidden region of the gravitational potential. This raises the question of whether the time of flight of a quantum particle in a gravitational field might deviate systematically from that of a classical particle due to tunnelling delay, representing a violation of the weak equivalence principle. I investigate this using a model quantum clock to measure the time of flight of a quantum particle in a uniform gravitational field, and show that a violation of the equivalence principle does not occur when the measurement is made far from the turning point of the classical trajectory. The results are then confirmed using the so-called dwell time definition of quantum tunnelling. I conclude with some remarks about the strong equivalence principle in quantum mechanics

  6. Quantum mechanics of a photon

    Science.gov (United States)

    Babaei, Hassan; Mostafazadeh, Ali

    2017-08-01

    A first-quantized free photon is a complex massless vector field A =(Aμ ) whose field strength satisfies Maxwell's equations in vacuum. We construct the Hilbert space H of the photon by endowing the vector space of the fields A in the temporal-Coulomb gauge with a positive-definite and relativistically invariant inner product. We give an explicit expression for this inner product, identify the Hamiltonian for the photon with the generator of time translations in H , determine the operators representing the momentum and the helicity of the photon, and introduce a chirality operator whose eigenfunctions correspond to fields having a definite sign of energy. We also construct a position operator for the photon whose components commute with each other and with the chirality and helicity operators. This allows for the construction of the localized states of the photon with a definite sign of energy and helicity. We derive an explicit formula for the latter and compute the corresponding electric and magnetic fields. These turn out to diverge not just at the point where the photon is localized but on a plane containing this point. We identify the axis normal to this plane with an associated symmetry axis and show that each choice of this axis specifies a particular position operator, a corresponding position basis, and a position representation of the quantum mechanics of a photon. In particular, we examine the position wave functions determined by such a position basis, elucidate their relationship with the Riemann-Silberstein and Landau-Peierls wave functions, and give an explicit formula for the probability density of the spatial localization of the photon.

  7. Multiplicative formulation of quantum mechanics

    International Nuclear Information System (INIS)

    Voros, A.; Leboeuf, P.

    1991-01-01

    A general semi-classical description for the eigenfunctions of the multidimensional Schroedinger operator cannot be based on the WKB method which is incompatible with classically ergodic behavior. An alternative, more general multiplicative parametrization of quantum wave functions is suggested, whereby the semi-classical behavior of eigenfunctions can be traced in the presence of classical ergodicity, in the form of diffusive patterns of phase-space zeros in the quantum wave functions. (author) 24 refs.; 4 figs

  8. Progress in post-quantum mechanics

    Science.gov (United States)

    Sarfatti, Jack

    2017-05-01

    Newton's mechanics in the 17th century increased the lethality of artillery. Thermodynamics in the 19th led to the steam-powered industrial revolution. Maxwell's unification of electricity, magnetism and light gave us electrical power, the telegraph, radio and television. The discovery of quantum mechanics in the 20th century by Planck, Bohr, Einstein, Schrodinger, Heisenberg led to the creation of the atomic and hydrogen bombs as well as computer chips, the world-wide-web and Silicon Valley's multibillion dollar corporations. The lesson is that breakthroughs in fundamental physics, both theoretical and experimental, have always led to profound technological wealth-creating industries and will continue to do so. There is now a new revolution brewing in quantum mechanics that can be divided into three periods. The first quantum revolution was from 1900 to about 1975. The second quantum information/computer revolution was from about 1975 to 2015. (The early part of this story is told by Kaiser in his book, How the Hippies Saved Physics, how a small group of Berkeley/San Francisco physicists triggered that second revolution.) The third quantum revolution is how an extension of quantum mechanics may lead to the understanding of consciousness as a natural physical phenomenon that can emerge in many material substrates, not only in our carbon-based biochemistry. In particular, this new post-quantum mechanics may lead to naturally conscious artificial intelligence in nano-electronic machines, as well as perhaps extending human life spans to hundreds of years and more.

  9. The metaphysics of quantum mechanics: Modal interpretations

    Science.gov (United States)

    Gluck, Stuart Murray

    2004-11-01

    This dissertation begins with the argument that a preferred way of doing metaphysics is through philosophy of physics. An understanding of quantum physics is vital to answering questions such as: What counts as an individual object in physical ontology? Is the universe fundamentally indeterministic? Are indiscernibles identical? This study explores how the various modal interpretations of quantum mechanics answer these sorts of questions; modal accounts are one of the two classes of interpretations along with so-called collapse accounts. This study suggests a new alternative within the class of modal views that yields a more plausible ontology, one in which the Principle of the Identity of Indisceribles is necessarily true. Next, it shows that modal interpretations can consistently deny that the universe must be fundamentally indeterministic so long as they accept certain other metaphysical commitments: either a perfect initial distribution of states in the universe or some form of primitive dispositional properties. Finally, the study sketches out a future research project for modal interpretations based on developing quantified quantum logic.

  10. Chaos. Possible underpinnings for quantum mechanics?

    International Nuclear Information System (INIS)

    McHarris, Wm.C.

    2004-01-01

    Alternative, parallel explanations for a number of counter-intuitive concepts connected with the foundations of quantum mechanics can be constructed in terms of nonlinear dynamics. These include ideas as diverse as the statistical exponential decay law and spontaneous symmetry breaking to decoherence itself and the inference from violations of Bell's inequality that local reality is ruled out in hidden variable extensions of quantum mechanics. Such alternative explanations must not be taken as demonstrations of nonlinear underpinnings for quantum mechanics, but they do raise the possibility of their existence. In this article I delve a bit into ideas connected with the exponential decay law and with Bell's inequality as demonstrations. Then an investigation of the Klein-Gordon equation shows that it should not come as a complete surprise that quantum mechanics just might contain fundamental nonlinearities. (author)

  11. Supersymmetric quantum mechanics and new potentials

    International Nuclear Information System (INIS)

    Drigo Filho, E.

    1988-01-01

    Using the supersymmetric quantum mechanics the following potential are generalized. The particle in the box, Poeschl-Teller and Rosen-Morse. The new potentials are evaluated and their eigenfunctions and spectra are indicated. (author) [pt

  12. Logical and mathematical structures of quantum mechanics

    International Nuclear Information System (INIS)

    Beltrametti, E.G.; Cassinelli, G.

    1976-01-01

    The logic associated with a physical system is first analysed, and the general properties of observable and states are discussed. The logic of the Hilbert-space formulation of quantum mechanics and of pure, ideal measurements is described

  13. Quantum mechanical streamlines. I - Square potential barrier

    Science.gov (United States)

    Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.

    1974-01-01

    Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.

  14. A fundamental equation in quantum mechanics

    International Nuclear Information System (INIS)

    Mackinnon, L.

    1981-01-01

    It is pointed out that the nondispersive de Broglie wave packet has a zero d'Alembertian, suggesting the possible reality of de Broglie waves and also that the field wave equation may be fundamental to Quantum Mechanics. (author)

  15. Advanced quantum mechanics materials and photons

    CERN Document Server

    Dick, Rainer

    2016-01-01

    In this updated and expanded second edition of a well-received and invaluable textbook, Prof. Dick emphasizes the importance of advanced quantum mechanics for materials science and all experimental techniques which employ photon absorption, emission, or scattering. Important aspects of introductory quantum mechanics are covered in the first seven chapters to make the subject self-contained and accessible for a wide audience. Advanced Quantum Mechanics, Materials and Photons can therefore be used for advanced undergraduate courses and introductory graduate courses which are targeted towards students with diverse academic backgrounds from the Natural Sciences or Engineering. To enhance this inclusive aspect of making the subject as accessible as possible Appendices A and B also provide introductions to Lagrangian mechanics and the covariant formulation of electrodynamics. This second edition includes an additional 62 new problems as well as expanded sections on relativistic quantum fields and applications of�...

  16. Science Academies' Refresher Course on Quantum Mechanics

    Indian Academy of Sciences (India)

    IAS Admin

    research scholars will be held at the Post-Graduate ... The Course is primarily aimed at teachers involved in teaching quantum mechanics at ... Module 2: Scattering, time-independent perturbations, WKB, variational method;. Module 3: Symmetries ...

  17. Approach to measurement to quantum mechanics

    International Nuclear Information System (INIS)

    Sudarshan, E.C.G.; Sherry, T.N.; Gautam, S.R.

    1977-10-01

    An unconventional approach to the measurement problem in quantum mechanics is considered, the apparatus is treated as a classical system, belonging to the macro-world. In order to have a measurement the apparatus must interact with the quantum system. As a first step, the classical apparatus is embedded into a larger quantum mechanical structure, making use of superselection rules. Projection back to the classical system is possible. The apparatus and system are now coupled such that the apparatus remains classical (principle of integrity), and unambiguous information of the values of a quantum observable are transferred to the variables of the apparatus. Finally, projection back to the classical formulation is accomplished. Further measurement of the classical apparatus can be done, causing no problems of principle. Thus interactions causing pointers to move (which are not treat) can be added. The restrictions placed by the principle of integrity on the form of the interaction between classical and quantum systems are examined

  18. Experimental status of quaternionic quantum mechanics

    International Nuclear Information System (INIS)

    Brumby, S.P.; Joshi, G.C.

    1995-01-01

    Analysis of the logical foundations of quantum mechanics indicates the possibility of constructing a theory using quaternionic Hilbert spaces. Whether this mathematical structure reflects reality is a matter for experiment to decide. The only direct search for quaternionic quantum mechanics yet carried out is reviewed and is proposed to look for quaternionic effects in correlated multi-particle systems. It is also discussed how such experiments might distinguish between the several quaternionic models proposed in the literature. 21 refs

  19. Uncertainty and complementarity in axiomatic quantum mechanics

    International Nuclear Information System (INIS)

    Lahti, P.J.

    1980-01-01

    An investigation of the uncertainty principle and the complementarity principle is carried through. The physical content of these principles and their representation in the conventional Hilbert space formulation of quantum mechanics forms a natural starting point. Thereafter is presented more general axiomatic framework for quantum mechanics, namely, a probability function formulation of the theory. Two extra axioms are stated, reflecting the ideas of the uncertainty principle and the complementarity principle, respectively. The quantal features of these axioms are explicated. (author)

  20. Formation of (DNA)2-LNA triplet with recombinant base recognition: A quantum mechanical study

    Science.gov (United States)

    Mall, Vijaya Shri; Tiwari, Rakesh Kumar

    2018-05-01

    The formation of DNA triple helix offers the verity of new possibilities in molecular biology. However its applications are limited to purine and pyrimidine rich sequences recognized by forming Hoogsteen/Reverse Hoogsteen triplets in major groove sites of DNA duplex. To overcome this drawback modification in bases backbone and glucose of nucleotide unit of DNA have been proposed so that the third strand base recognized by both the bases of DNA duplex by forming Recombinant type(R-type) of bonding in mixed sequences. Here we performed Quanrum Mechanical (Hartree-Fock and DFT) methodology on natural DNA and Locked Nucleic Acids(LNA) triplets using 6-31G and some other new advance basis sets. Study suggests energetically stable conformation has been observed for recombinant triplets in order of G-C*G > A-T*A > G-C*C > T-A*T for both type of triplets. Interestingly LNA leads to more stable conformation in all set of triplets, clearly suggests an important biological tool to overcome above mentioned drawbacks.

  1. Elements of non-relativistic quantum mechanics

    CERN Document Server

    Sobrino, Luis

    1996-01-01

    This book presents the basic structure of quantum mechanics, the elements needed to properly understand the subject and its applications. It is written at a level which is intermediate between the standard graduate textbooks, which it intends to supplement, and the more advanced mathematical writings in the subject. Particular attention is given to the concepts of kinematical and dynamical symmetries. The unifying thread that links the study of particles and systems of particles is the connection between Galilean invariance and the fundamental observables of a system. The mathematical appendic

  2. Noncommutative quantum mechanics and Bohm's ontological interpretation

    International Nuclear Information System (INIS)

    Barbosa, G.D.; Pinto-Neto, N.

    2004-01-01

    We carry out an investigation into the possibility of developing a Bohmian interpretation based on the continuous motion of point particles for noncommutative quantum mechanics. The conditions for such an interpretation to be consistent are determined, and the implications of its adoption for noncommutativity are discussed. A Bohmian analysis of the noncommutative harmonic oscillator is carried out in detail. By studying the particle motion in the oscillator orbits, we show that small-scale physics can have influence at large scales, something similar to the IR-UV mixing

  3. On quantum mechanical decay processes

    Energy Technology Data Exchange (ETDEWEB)

    Grummt, Robert

    2013-12-18

    This thesis is concerned with quantum mechanical decay processes and their mathematical description. It consists out of three parts: In the first part we look at Laser induced ionization, whose mathematical description is often based on the so-called dipole approximation. Employing it essentially means to replace the Laser's vector potential A(r,t) in the Hamiltonian by A(0,t). Heuristically this is justified under usual experimental conditions, because the Laser varies only slowly in r on atomic length scales. We make this heuristics rigorous by proving the dipole approximation in the limit in which the Laser's length scale becomes infinite compared to the atomic length scale. Our results apply to N-body Hamiltonians. In the second part we look at alpha decay as described by Skibsted (Comm. Math. Phys. 104, 1986) and show that Skibsted's model satisfies an energy-time uncertainty relation. Since there is no self-adjoint time operator, the uncertainty relation for energy and time can not be proven in the same way as the uncertainty relation for position and momentum. To define the time variance without a self-adjoint time operator, we will use the arrival time distribution obtained from the quantum current. Our proof of the energy-time uncertainty relation is then based on the quantitative scattering estimates that will be derived in the third part of the thesis and on a result from Skibsted. In addition to that, we will show that this uncertainty relation is different from the well known linewidth-lifetime relation. The third part is about quantitative scattering estimates, which are of interest in their own right. For rotationally symmetric potentials having support in [0,R{sub V}] we will show that for R≥R{sub V}, the time evolved wave function e{sup -iHt}ψ satisfies parallel 1{sub R}e{sup -iHt}ψ parallel {sup 2}{sub 2}≤c{sub 1}t{sup -1}+c{sub 2}t{sup -2}+c{sub 3}t{sup -3}+c{sub 4}t{sup -4} with explicit quantitative bounds on the constants

  4. Extracontextuality and extravalence in quantum mechanics.

    Science.gov (United States)

    Auffèves, Alexia; Grangier, Philippe

    2018-07-13

    We develop the point of view where quantum mechanics results from the interplay between the quantized number of 'modalities' accessible to a quantum system, and the continuum of 'contexts' that are required to define these modalities. We point out the specific roles of 'extracontextuality' and 'extravalence' of modalities, and relate them to the Kochen-Specker and Gleason theorems.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).

  5. Horizon quantum mechanics of rotating black holes

    Energy Technology Data Exchange (ETDEWEB)

    Casadio, Roberto [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); I.N.F.N., Sezione di Bologna, I.S. FLAG, Bologna (Italy); Giugno, Andrea [Ludwig-Maximilians-Universitaet, Arnold Sommerfeld Center, Munich (Germany); Giusti, Andrea [Universita di Bologna, Dipartimento di Fisica e Astronomia, Bologna (Italy); I.N.F.N., Sezione di Bologna, I.S. FLAG, Bologna (Italy); Ludwig-Maximilians-Universitaet, Arnold Sommerfeld Center, Munich (Germany); Micu, Octavian [Institute of Space Science, Bucharest, P.O. Box MG-23, Bucharest-Magurele (Romania)

    2017-05-15

    The horizon quantum mechanics is an approach that was previously introduced in order to analyze the gravitational radius of spherically symmetric systems and compute the probability that a given quantum state is a black hole. In this work, we first extend the formalism to general space-times with asymptotic (ADM) mass and angular momentum. We then apply the extended horizon quantum mechanics to a harmonic model of rotating corpuscular black holes. We find that simple configurations of this model naturally suppress the appearance of the inner horizon and seem to disfavor extremal (macroscopic) geometries. (orig.)

  6. Quantum mechanics of charged particle beam optics

    CERN Document Server

    Khan, Sameen Ahmed

    2018-01-01

    Theory of charged particle beam optics is basic to the design and working of charged particle beam devices from electron microscopes to accelerator machines. Traditionally, the optical elements of the devices are designed and operated based on classical mechanics and classical electromagnetism, and only certain specific quantum mechanical aspects are dealt with separately using quantum theory. This book provides a systematic approach to quantum theory of charged particle beam optics, particularly in the high energy cases such as accelerators or high energy electron microscopy.

  7. Nonlocality and localizability in quantum mechanics

    International Nuclear Information System (INIS)

    Matsuno, K.

    1989-01-01

    Nonlocality of simultaneous spatial correlation of a quantum phenomenon as demonstrated in various versions of Einstein-Podolsky-Rosen type experiment reduces to nonlocality of the measurement apparatus in the sense that the eigen-wavefunctions for the apparatus are completely specified in a manner of being independent of whatever object it may measure. Nonlocality of the measurement apparatus however serves as no more than a good approximation to reality at best. The theoretical imposition of nonlocality of the measurement apparatus as an approximation is compatible with the actual locality of quantum mechanics that dispenses with an agent claiming globally simultaneous specifiability of boundary conditions, though the genuine locality of quantum mechanics has to be examined without employing the nonlocality of the measurement apparatus. The actual locality of quantum mechanics is intrinsically irreversible in its development

  8. Bell trajectories for revealing quantum control mechanisms

    International Nuclear Information System (INIS)

    Dennis, Eric; Rabitz, Herschel

    2003-01-01

    The dynamics induced while controlling quantum systems by optimally shaped laser pulses have often been difficult to understand in detail. A method is presented for quantifying the importance of specific sequences of quantum transitions involved in the control process. The method is based on a ''beable'' formulation of quantum mechanics due to John Bell that rigorously maps the quantum evolution onto an ensemble of stochastic trajectories over a classical state space. Detailed mechanism identification is illustrated with a model seven-level system. A general procedure is presented to extract mechanism information directly from closed-loop control experiments. Application to simulated experimental data for the model system proves robust with up to 25% noise

  9. Moessbauer neutrinos in quantum mechanics and quantum field theory

    International Nuclear Information System (INIS)

    Kopp, Joachim

    2009-01-01

    We demonstrate the correspondence between quantum mechanical and quantum field theoretical descriptions of Moessbauer neutrino oscillations. First, we compute the combined rate Γ of Moessbauer neutrino emission, propagation, and detection in quantum field theory, treating the neutrino as an internal line of a tree level Feynman diagram. We include explicitly the effect of homogeneous line broadening due to fluctuating electromagnetic fields in the source and detector crystals and show that the resulting formula for Γ is identical to the one obtained previously [1] for the case of inhomogeneous line broadening. We then proceed to a quantum mechanical treatment of Moessbauer neutrinos and show that the oscillation, coherence, and resonance terms from the field theoretical result can be reproduced if the neutrino is described as a superposition of Lorentz-shaped wave packet with appropriately chosen energies and widths. On the other hand, the emission rate and the detection cross section, including localization and Lamb-Moessbauer terms, cannot be predicted in quantum mechanics and have to be put in by hand.

  10. Applications of quantum mechanical techniques to areas outside of quantum mechanics

    CERN Document Server

    Khrennikov, Andrei

    2018-01-01

    This book deals with applications of quantum mechanical techniques to areas outside of quantum mechanics, so-called quantum-like modeling. Research in this area has grown over the last 15 years. But even already more than 50 years ago, the interaction between Physics Nobelist Pauli and the psychologist Carl Jung in the 1950's on seeking to find analogous uses of the complementarity principle from quantum mechanics in psychology needs noting. This book does NOT want to advance that society is quantum mechanical! The macroscopic world is manifestly not quantum mechanical. But this rules not out that one can use concepts and the mathematical apparatus from quantum physics in a macroscopic environment. A mainstay ingredient of quantum mechanics, is 'quantum probability' and this tool has been proven to be useful in the mathematical modelling of decision making. In the most basic experiment of quantum physics, the double slit experiment, it is known (from the works of A. Khrennikov) that the law of total probabi...

  11. Solvent dielectric effect and side chain mutation on the structural stability of Burkholderia cepacia lipase active site: a quantum mechanical/molecular mechanics study.

    Science.gov (United States)

    Tahan, A; Monajjemi, M

    2011-12-01

    Quantum mechanical and molecular dynamics methods were used to analyze the structure and stability of neutral and zwitterionic configurations of the extracted active site sequence from a Burkholderia cepacia lipase, histidyl-seryl-glutamin (His86-Ser87-Gln88) and its mutated form, histidyl-cysteyl-glutamin (His86-Cys87-Gln88) in vacuum and different solvents. The effects of solvent dielectric constant, explicit and implicit water molecules and side chain mutation on the structure and stability of this sequence in both neutral and zwitterionic forms are represented. The quantum mechanics computations represent that the relative stability of zwitterionic and neutral configurations depends on the solvent structure and its dielectric constant. Therefore, in vacuum and the considered non-polar solvents, the neutral form of the interested sequences is more stable than the zwitterionic form, while their zwitterionic form is more stable than the neutral form in the aqueous solution and the investigated polar solvents in most cases. However, on the potential energy surfaces calculated, there is a barrier to proton transfer from the positively charged ammonium group to the negatively charged carboxylat group or from the ammonium group to the adjacent carbonyl oxygen and or from side chain oxygen and sulfur to negatively charged carboxylat group. Molecular dynamics simulations (MD) were also performed by using periodic boundary conditions for the zwitterionic configuration of the hydrated molecules in a box of water molecules. The obtained results demonstrated that the presence of explicit water molecules provides the more compact structures of the studied molecules. These simulations also indicated that side chain mutation and replacement of sulfur with oxygen leads to reduction of molecular flexibility and packing.

  12. On quantum chaos, stochastic webs and localization in a quantum mechanical kick system

    International Nuclear Information System (INIS)

    Engel, U.M.

    2007-01-01

    In this study quantum chaos is discussed using the kicked harmonic oscillator as a model system. The kicked harmonic oscillator is characterized by an exceptional scenario of weak chaos: In the case of resonance between the frequency of the harmonic oscillator and the frequency of the periodic forcing, stochastic webs in phase space are generated by the classical dynamics. For the quantum dynamics of this system it is shown that the resulting Husimi distributions in quantum phase space exhibit the same web-like structures as the classical webs. The quantum dynamics is characterized by diffusive energy growth - just as the classical dynamics in the channels of the webs. In the case of nonresonance, the classically diffusive dynamics is found to be quantum mechanically suppressed. This bounded energy growth, which corresponds to localization in quantum phase space, is explained analytically by mapping the system onto the Anderson model. In this way, within the context of quantum chaos, the kicked harmonic oscillator is characterized by exhibiting its noteworthy geometrical and dynamical properties both classically and quantum mechanically, while at the same time there are also very distinct quantum deviations from classical properties, the most prominent example being quantum localization. (orig.)

  13. Quantum mechanics and the science of measurements

    International Nuclear Information System (INIS)

    Ramsey, N.F.

    1992-01-01

    The accuracies of measurements of almost all fundamental physical constants have increased by factors of about 10,000 during the past 60 years. Although some of the improvements are due to greater care, most are due to new techniques based on quantum mechanics. In popular accounts of quantum mechanics, such great emphases is placed on the Heisenberg Uncertainty Principle that it often appears that the primary effect of quantum mechanics should be to diminish measurement accuracy whereas in most cases it is the validity of quantum mechanics that makes possible the vastly improved measurement accuracies. Seven quantum features that have a profound influence on the science of measurements are: (1) Existence of discrete quantum states of energy W i . (2) Energy conservation in transitions between two states. (3) Electromagnetic radiation of frequency ν is quantized with energy hν per quantum. (4) The identity principle. (5) The Heisenberg Uncertainty Principle. (6) Addition of probability amplitudes (not probabilities) so P=vertical strokeψ 1 +ψ 2 vertical stroke 2 ≠vertical strokeψ 1 vertical stroke 2 +vertical strokeψ 2 vertical stroke 2 . (7) Wave and coherent phase phenomena. Of these seven quantum features, only the Heisenberg Uncertainty Principle limits the accuracy of measurements, and its affect is often negligibly small. The other six features make possible much more accurate measurements of quantum systems than with almost all classical systems and the identity principle provides meaning and significance to highly precise measurements with quantized systems. These effects are discussed and illustrated. (orig.)

  14. Mind, matter, and quantum mechanics

    International Nuclear Information System (INIS)

    Stapp, H.P.

    1982-01-01

    A theory of psychophysical phenomena is proposed. It resolves simultaneously four basic problems of science, namely the problems of the connections between: (1) mind and matter, (2), quantum theory and reality, (3) relativity theory and ''becoming,'' and (4) relativity theory and Bell's theorem

  15. A "Bit" of Quantum Mechanics

    Science.gov (United States)

    Oss, Stefano; Rosi, Tommaso

    2015-01-01

    We have developed an app for iOS-based smart-phones/tablets that allows a 3-D, complex phase-based colorful visualization of hydrogen atom wave functions. Several important features of the quantum behavior of atomic orbitals can easily be made evident, thus making this app a useful companion in introductory modern physics classes. There are many…

  16. How to teach quantum mechanics

    International Nuclear Information System (INIS)

    Passon, Oliver

    2004-01-01

    In the spirit and style of John S Bell's well-known paper on How to teach special relativity it is argued that a 'Bohmian pedagogy' provides a very useful tool to illustrate the relation between classical and quantum physics and illuminates the peculiar features of the latter

  17. How to teach quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Passon, Oliver [Fachbereich Physik, University of Wuppertal, Postfach 100127, 42097 Wuppertal (Germany)

    2004-11-01

    In the spirit and style of John S Bell's well-known paper on How to teach special relativity it is argued that a 'Bohmian pedagogy' provides a very useful tool to illustrate the relation between classical and quantum physics and illuminates the peculiar features of the latter.

  18. On the hypothesis that quantum mechanism manifests classical mechanics: Numerical approach to the correspondence in search of quantum chaos

    International Nuclear Information System (INIS)

    Lee, Sang-Bong.

    1993-09-01

    Quantum manifestation of classical chaos has been one of the extensively studied subjects for more than a decade. Yet clear understanding of its nature still remains to be an open question partly due to the lack of a canonical definition of quantum chaos. The classical definition seems to be unsuitable in quantum mechanics partly because of the Heisenberg quantum uncertainty. In this regard, quantum chaos is somewhat misleading and needs to be clarified at the very fundamental level of physics. Since it is well known that quantum mechanics is more fundamental than classical mechanics, the quantum description of classically chaotic nature should be attainable in the limit of large quantum numbers. The focus of my research, therefore, lies on the correspondence principle for classically chaotic systems. The chaotic damped driven pendulum is mainly studied numerically using the split operator method that solves the time-dependent Schroedinger equation. For classically dissipative chaotic systems in which (multi)fractal strange attractors often emerge, several quantum dissipative mechanisms are also considered. For instance, Hoover's and Kubo-Fox-Keizer's approaches are studied with some computational analyses. But the notion of complex energy with non-Hermiticity is extensively applied. Moreover, the Wigner and Husimi distribution functions are examined with an equivalent classical distribution in phase-space, and dynamical properties of the wave packet in configuration and momentum spaces are also explored. The results indicate that quantum dynamics embraces classical dynamics although the classicalquantum correspondence fails to be observed in the classically chaotic regime. Even in the semi-classical limits, classically chaotic phenomena would eventually be suppressed by the quantum uncertainty

  19. Quantum-mechanical scattering in one dimension

    International Nuclear Information System (INIS)

    Boya, Luis J.

    2008-01-01

    The purpose of this mainly pedagogical review is to fill a lacuna in the usual treatment of scattering in quantum mechanics, by showing the essential of it in the simplest, one-dimensional setting. We define in this situation amplitudes and scattering coefficients and deal with optical and Levinson' theorems as consequences of unitarity in coordinate or momentum space. Parity waves en lieu of partial waves, integral equations and Born series, etc., are defined naturally in this frame. Several solvable examples are shown. Two topics best studied in 1d are transparent potentials and supersymmetric quantum mechanics. Elementary analytical properties and general behaviour of amplitudes give rise to study inverse problems, that is, recovering the potential from scattering data. Isospectral deformations of the wave equation give relations with some nonlinear evolution equations (Lax), solvable by the inverse scattering method (Kruskal), and we consider the KdV equation as an example. We also refer briefly to some singular potentials, where, e.g., the essence of renormalization can be read off again in the simplest setting. The whole paper emphasizes the tutorial and introductory aspects

  20. An introduction to the tomographic picture of quantum mechanics

    International Nuclear Information System (INIS)

    Ibort, A; Man'ko, V I; Marmo, G; Simoni, A; Ventriglia, F

    2009-01-01

    Starting from the famous Pauli problem on the possibility of associating quantum states with probabilities, the formulation of quantum mechanics in which quantum states are described by fair probability distributions (tomograms, i.e. tomographic probabilities) is reviewed in a pedagogical style. The relation between the quantum state description and the classical state description is elucidated. The difference between those sets of tomograms is described by inequalities equivalent to a complete set of uncertainty relations for the quantum domain and to non-negativity of probability density on phase space in the classical domain. The intersection of such sets is studied. The mathematical mechanism that allows us to construct different kinds of tomographic probabilities like symplectic tomograms, spin tomograms, photon number tomograms, etc is clarified and a connection with abstract Hilbert space properties is established. The superposition rule and uncertainty relations in terms of probabilities as well as quantum basic equations like quantum evolution and energy spectra equations are given in an explicit form. A method to check experimentally the uncertainty relations is suggested using optical tomograms. Entanglement phenomena and the connection with semigroups acting on simplexes are studied in detail for spin states in the case of two-qubits. The star-product formalism is associated with the tomographic probability formulation of quantum mechanics.

  1. Quantum mechanics.Text and exercise book. 2. upd. ed.

    International Nuclear Information System (INIS)

    Griffiths, David J.

    2012-01-01

    The modern life would be without quantum mechanics no more imaginable - on their laws are founded transistors, computer chips, mobile telephones, flat displays, and numerous other things of daily life. An understanding of this theory is indispensable in order to be able to settle a matter with questions of temporary physics. Griffith's ''Intorduction to Quantum Mechanics'' presents the fundamental laws of quantum mechanics, puts carefully the mathematical foundations of the theory, and presents essential applications of quantum mechanics from the hydrogen atom until Schroedinger's cat. This book applies to studyings of natural sciences, especially of physics. It is concipated for studyings of bachelor courses at universities and throws a bridge between the conceptual core of quantum mechanics and the mathematically often expensive application to real problems. For this numerous problems are completely worked out in order to fill the matter with life. Rounded off are all chapters by a manifold of problems of all degrees of difficulty, which allow the studyings to deepen their knowledge and apply immediately. Beside a course accompanying the ''Introduction to Quantum Mechanics'' is therefore also suited for the self-study.

  2. Quantum mechanics and dynamics in phase space

    International Nuclear Information System (INIS)

    Zlatev, I.S.

    1979-01-01

    Attention is paid to formal similarity of quantum mechanics and classical statistical physics. It is supposed that quantum mechanics can be reformulated by means of the quasiprobabilistic distributions (QPD). The procedure of finding a possible dynamics of representative points in a phase space is described. This procedure would lead to an equation of the Liouville type for the given QPD. It is shown that there is always a dynamics for which the phase volume is preserved and there is another dynamics for which the equations of motion are ''canonical''. It follows from the paper that in terms of the QPD the quantum mechanics is analogous to the classical statistical mechanics and it can be interpreted as statistics of phase points, their motion obeying the canonical equations. The difference consists in the fact that in the classical statistical physics constructed is statistics of points in a phase space which depict real, existing, observable states of the system under consideration. In the quantum mechanics constructed is statistics of points in a phase space which correspond to the ''substrate'' of quantum-mechanical objects which have no any physical sense and cannot be observed separately

  3. Nilpotent Quantum Mechanics: Analogs and Applications

    Directory of Open Access Journals (Sweden)

    Peter Marcer

    2017-07-01

    Full Text Available The most significant characteristic of nilpotent quantum mechanics is that the quantum system (fermion state and its environment (vacuum are, in mathematical terms, mirror images of each other. So a change in one automatically leads to corresponding changes in the other. We have used this characteristic as a model for self-organization, which has applications well beyond quantum physics. The nilpotent structure has also been identified as being constructed from two commutative vector spaces. This zero square-root construction has a number of identifiable characteristics which we can expect to find in systems where self-organization is dominant, and a case presented after the publication of a paper by us on “The ‘Logic’ of Self-Organizing Systems” [1], in the organization of the neurons in the visual cortex. We expect to find many more complex systems where our general principles, based, by analogy, on nilpotent quantum mechanics, will apply.

  4. Optimal guidance law in quantum mechanics

    International Nuclear Information System (INIS)

    Yang, Ciann-Dong; Cheng, Lieh-Lieh

    2013-01-01

    Following de Broglie’s idea of a pilot wave, this paper treats quantum mechanics as a problem of stochastic optimal guidance law design. The guidance scenario considered in the quantum world is that an electron is the flight vehicle to be guided and its accompanying pilot wave is the guidance law to be designed so as to guide the electron to a random target driven by the Wiener process, while minimizing a cost-to-go function. After solving the stochastic optimal guidance problem by differential dynamic programming, we point out that the optimal pilot wave guiding the particle’s motion is just the wavefunction Ψ(t,x), a solution to the Schrödinger equation; meanwhile, the closed-loop guidance system forms a complex state–space dynamics for Ψ(t,x), from which quantum operators emerge naturally. Quantum trajectories under the action of the optimal guidance law are solved and their statistical distribution is shown to coincide with the prediction of the probability density function Ψ ∗ Ψ. -- Highlights: •Treating quantum mechanics as a pursuit-evasion game. •Reveal an interesting analogy between guided flight motion and guided quantum motion. •Solve optimal quantum guidance problem by dynamic programming. •Gives a formal proof of de Broglie–Bohm’s idea of a pilot wave. •The optimal pilot wave is shown to be a wavefunction solved from Schrödinger equation

  5. Optimal guidance law in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ciann-Dong, E-mail: cdyang@mail.ncku.edu.tw; Cheng, Lieh-Lieh, E-mail: leo8101@hotmail.com

    2013-11-15

    Following de Broglie’s idea of a pilot wave, this paper treats quantum mechanics as a problem of stochastic optimal guidance law design. The guidance scenario considered in the quantum world is that an electron is the flight vehicle to be guided and its accompanying pilot wave is the guidance law to be designed so as to guide the electron to a random target driven by the Wiener process, while minimizing a cost-to-go function. After solving the stochastic optimal guidance problem by differential dynamic programming, we point out that the optimal pilot wave guiding the particle’s motion is just the wavefunction Ψ(t,x), a solution to the Schrödinger equation; meanwhile, the closed-loop guidance system forms a complex state–space dynamics for Ψ(t,x), from which quantum operators emerge naturally. Quantum trajectories under the action of the optimal guidance law are solved and their statistical distribution is shown to coincide with the prediction of the probability density function Ψ{sup ∗}Ψ. -- Highlights: •Treating quantum mechanics as a pursuit-evasion game. •Reveal an interesting analogy between guided flight motion and guided quantum motion. •Solve optimal quantum guidance problem by dynamic programming. •Gives a formal proof of de Broglie–Bohm’s idea of a pilot wave. •The optimal pilot wave is shown to be a wavefunction solved from Schrödinger equation.

  6. Empirical logic and quantum mechanics

    International Nuclear Information System (INIS)

    Foulis, D.J.; Randall, C.H.

    1976-01-01

    This article discusses some of the basic notions of quantum physics within the more general framework of operational statistics and empirical logic (as developed in Foulis and Randall, 1972, and Randall and Foulis, 1973). Empirical logic is a formal mathematical system in which the notion of an operation is primitive and undefined; all other concepts are rigorously defined in terms of such operations (which are presumed to correspond to actual physical procedures). (Auth.)

  7. QSAR, docking, dynamic simulation and quantum mechanics studies to explore the recognition properties of cholinesterase binding sites.

    Science.gov (United States)

    Correa-Basurto, J; Bello, M; Rosales-Hernández, M C; Hernández-Rodríguez, M; Nicolás-Vázquez, I; Rojo-Domínguez, A; Trujillo-Ferrara, J G; Miranda, René; Flores-Sandoval, C A

    2014-02-25

    A set of 84 known N-aryl-monosubstituted derivatives (42 amides: series 1 and 2, and 42 imides: series 3 an 4, from maleic and succinic anhydrides, respectively) that display inhibitory activity toward both acetylcholinesterase and butyrylcholinesterase (ChEs) was considered for Quantitative structure-activity relationship (QSAR) studies. These QSAR studies employed docking data from both ChEs that were previously submitted to molecular dynamics (MD) simulations. Donepezil and galanthamine stereoisomers were included to analyze their quantum mechanics properties and for validating the docking procedure. Quantum parameters such as frontier orbital energies, dipole moment, molecular volume, atomic charges, bond length and reactivity parameters were measured, as well as partition coefficients, molar refractivity and polarizability were also analyzed. In order to evaluate the obtained equations, four compounds: 1a (4-oxo-4-(phenylamino)butanoic acid), 2a ((2Z)-4-oxo-4-(phenylamino)but-2-enoic acid), 3a (2-phenylcyclopentane-1,3-dione) and 4a (2-phenylcyclopent-4-ene-1,3-dione) were employed as independent data set, using only equations with r(m(test))²>0.5. It was observed that residual values gave low value in almost all series, excepting in series 1 for compounds 3a and 4a, and in series 4 for compounds 1a, 2a and 3a, giving a low value for 4a. Consequently, equations seems to be specific according to the structure of the evaluated compound, that means, series 1 fits better for compound 1a, series 3 or 4 fits better for compounds 3a or 4a. Same behavior was observed in the butyrylcholinesterase (BChE). Therefore, obtained equations in this QSAR study could be employed to calculate the inhibition constant (Ki) value for compounds having a similar structure as N-aryl derivatives described here. The QSAR study showed that bond lengths, molecular electrostatic potential and frontier orbital energies are important in both ChE targets. Docking studies revealed that

  8. Quantum mechanical wavefunction: visualization at undergraduate level

    International Nuclear Information System (INIS)

    Chhabra, Mahima; Das, Ritwick

    2017-01-01

    Quantum mechanics (QM) forms the most crucial ingredient of modern-era physical science curricula at undergraduate level. The abstract ideas involved in QM related concepts pose a challenge towards appropriate visualization as a consequence of their counter-intuitive nature and lack of experiment-assisted visualization tools. At the heart of the quantum mechanical formulation lies the concept of ‘wavefunction’, which forms the basis for understanding the behavior of physical systems. At undergraduate level, the concept of ‘wavefunction’ is introduced in an abstract framework using mathematical tools and therefore opens up an enormous scope for alternative conceptions and erroneous visualization. The present work is an attempt towards exploring the visualization models constructed by undergraduate students for appreciating the concept of ‘wavefunction’. We present a qualitative analysis of the data obtained from administering a questionnaire containing four visualization based questions on the topic of ‘wavefunction’ to a group of ten undergraduate-level students at an institute in India which excels in teaching and research of basic sciences. Based on the written responses, all ten students were interviewed in detail to unravel the exact areas of difficulty in visualization of ‘wavefunction’. The outcome of present study not only reveals the gray areas in students’ conceptualization, but also provides a plausible route to address the issues at the pedagogical level within the classroom. (paper)

  9. Quantum mechanical wavefunction: visualization at undergraduate level

    Science.gov (United States)

    Chhabra, Mahima; Das, Ritwick

    2017-01-01

    Quantum mechanics (QM) forms the most crucial ingredient of modern-era physical science curricula at undergraduate level. The abstract ideas involved in QM related concepts pose a challenge towards appropriate visualization as a consequence of their counter-intuitive nature and lack of experiment-assisted visualization tools. At the heart of the quantum mechanical formulation lies the concept of ‘wavefunction’, which forms the basis for understanding the behavior of physical systems. At undergraduate level, the concept of ‘wavefunction’ is introduced in an abstract framework using mathematical tools and therefore opens up an enormous scope for alternative conceptions and erroneous visualization. The present work is an attempt towards exploring the visualization models constructed by undergraduate students for appreciating the concept of ‘wavefunction’. We present a qualitative analysis of the data obtained from administering a questionnaire containing four visualization based questions on the topic of ‘wavefunction’ to a group of ten undergraduate-level students at an institute in India which excels in teaching and research of basic sciences. Based on the written responses, all ten students were interviewed in detail to unravel the exact areas of difficulty in visualization of ‘wavefunction’. The outcome of present study not only reveals the gray areas in students’ conceptualization, but also provides a plausible route to address the issues at the pedagogical level within the classroom.

  10. Advanced quantum mechanics materials and photons

    CERN Document Server

    Dick, Rainer

    2012-01-01

    Advanced Quantum Mechanics: Materials and Photons is a textbook which emphasizes the importance of advanced quantum mechanics for materials science and all experimental techniques which employ photon absorption, emission, or scattering. Important aspects of introductory quantum mechanics are covered in the first seven chapters to make the subject self-contained and accessible for a wide audience. The textbook can therefore be used for advanced undergraduate courses and introductory graduate courses which are targeted towards students with diverse academic backgrounds from the Natural Sciences or Engineering. To enhance this inclusive aspect of making the subject as accessible as possible, Appendices A and B also provide introductions to Lagrangian mechanics and the covariant formulation of electrodynamics. Other special features include an introduction to Lagrangian field theory and an integrated discussion of transition amplitudes with discrete or continuous initial or final states. Once students have acquir...

  11. Quantum mechanics: why complex Hilbert space?

    Science.gov (United States)

    Cassinelli, G; Lahti, P

    2017-11-13

    We outline a programme for an axiomatic reconstruction of quantum mechanics based on the statistical duality of states and effects that combines the use of a theorem of Solér with the idea of symmetry. We also discuss arguments favouring the choice of the complex field.This article is part of the themed issue 'Second quantum revolution: foundational questions'. © 2017 The Author(s).

  12. The conceptual foundations of quantum mechanics

    CERN Document Server

    Eisenbud, Leonard

    2007-01-01

    This book provides a clear and logical path to understanding what quantum mechanics is about. It will be accessible to undergraduates with minimal mathematical preparation: all that is required is an open mind, a little algebra, and a first course in undergraduate physics. Quantum mechanics is arguably the most successful physical theory. It makes predictions of incredible accuracy. It provides the structure underlying all of our electronic technology, and much of our mastery over materials. But compared with Newtonian mechanics, or even relativity, its teachings seem obscure-they have no coun

  13. Quantum mechanics as applied mathematical statistics

    International Nuclear Information System (INIS)

    Skala, L.; Cizek, J.; Kapsa, V.

    2011-01-01

    Basic mathematical apparatus of quantum mechanics like the wave function, probability density, probability density current, coordinate and momentum operators, corresponding commutation relation, Schroedinger equation, kinetic energy, uncertainty relations and continuity equation is discussed from the point of view of mathematical statistics. It is shown that the basic structure of quantum mechanics can be understood as generalization of classical mechanics in which the statistical character of results of measurement of the coordinate and momentum is taken into account and the most important general properties of statistical theories are correctly respected.

  14. Theoretical physics vol. 2. Quantum mechanics, relativistic quantum mechanics, quantum field theory, elementar-particle theory, thermodynamics and statistics

    International Nuclear Information System (INIS)

    Rebhan, E.

    2005-01-01

    The present second volume treats quantum mechanics, relativistic quantum mechanics, the foundations of quantum-field and elementary-particle theory as well as thermodynamics and statistics. Both volumes comprehend all fields, which are usually offered in a course about theoretical physics. In all treated fields a very careful introduction to the basic natural laws forms the starting point, whereby it is thoroughly analysed, which of them is based on empirics, which is logically deducible, and which role play basic definitions. Extendingly the matter extend of the corresponding courses starting from the relativistic quantum theory an introduction to the elementary particles is developed. All problems are very thoroughly and such extensively studied, that each step is singularly reproducible. On motivation and good understandability is cared much about. The mixing of mathematical difficulties with problems of physical nature often obstructive in the learning is so circumvented, that important mathematical methods are presented in own chapters (for instance Hilbert spaces, Lie groups). By means of many examples and problems (for a large part with solutions) the matter worked out is deepened and exercised. Developments, which are indeed important, but seem for the first approach abandonable, are pursued in excurses. This book starts from courses, which the author has held at the Heinrich-Heine university in Duesseldorf, and was in many repetitions fitted to the requirements of the students. It is conceived in such a way, that it is also after the study suited as dictionary or for the regeneration

  15. Para-bosons and Para-fermions in Quantum Mechanics

    International Nuclear Information System (INIS)

    Cattani, M.S.D.; Fernandes, N.C.

    1982-01-01

    Within the framework of the ordinary quantum mechanics, a detailed study of the energy eigenfunctions of N identical particles using the irreducible representations of the permutation group in the Hilbert space is performed. It is shown that the para-states, as occurs with the boson and fermion states, are compatible with the postulates of quantum mechanics and with the principle of indistinguishability. A mathematical support for the existence of para-bosons and para-fermions is given. Gentile's quantum statistics is, in a certain sense, justified. (Author) [pt

  16. Quantum mechanical effects in plasmonic structures with subnanometre gaps.

    Science.gov (United States)

    Zhu, Wenqi; Esteban, Ruben; Borisov, Andrei G; Baumberg, Jeremy J; Nordlander, Peter; Lezec, Henri J; Aizpurua, Javier; Crozier, Kenneth B

    2016-06-03

    Metallic structures with nanogap features have proven highly effective as building blocks for plasmonic systems, as they can provide a wide tuning range of operating frequencies and large near-field enhancements. Recent work has shown that quantum mechanical effects such as electron tunnelling and nonlocal screening become important as the gap distances approach the subnanometre length-scale. Such quantum effects challenge the classical picture of nanogap plasmons and have stimulated a number of theoretical and experimental studies. This review outlines the findings of many groups into quantum mechanical effects in nanogap plasmons, and discusses outstanding challenges and future directions.

  17. Intrinsic resonance representation of quantum mechanics

    DEFF Research Database (Denmark)

    Carioli, M.; Heller, E.J.; Møller, Klaus Braagaard

    1997-01-01

    an optimal representation, based purely on classical mechanics. ''Hidden'' constants of the motion and good actions already known to the classical mechanics are thus incorporated into the basis, leaving the quantum effects to be isolated and included by small matrix diagonalizations. This simplifies...

  18. A quantum-mechanical study of ZnO and TiO2 based dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cicero, Giancarlo [Chemical Engineering and Materials Science Department, Politecnico of Torino, Torino (Italy); Mallia, Giuseppe; Liborio, Leandro [Imperial College London, Thomas Young Centre, Chemistry Department, London (United Kingdom); Harrison, Nicholas M. [Imperial College London, Thomas Young Centre, Chemistry Department, London (United Kingdom); STFC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom)

    2010-07-01

    Since the pioneering work of Regan and Graetzel, a great attention has been paid to dye sensitized solar cell (DSC) as cheap, effective and environmentally benign candidates for a new generation solar power devices. Optimization of the DSC is still a challenging task as it is a highly complex interacting molecular system. Surface properties of the oxide and in particular proper sensitization with dye molecules may highly affect the efficiency of these cells. Aim of this study is to address the binding of cathecol and isonicotinic acid to oxide surfaces usually employed in DSC, namely ZnO and TiO{sub 2}, in terms of geometry, stability, electronic structure and band alignment. To this end, we employ quantum mechanical simulations based on hybrid density functional theory. Our analysis helps understanding whether the difference between ZnO and TiO{sub 2} in photoeletricity generation efficiency is due to the changes in the bonding geometry of the dye anchoring groups or to electronic effects.

  19. Quantum mechanics and quantum information a guide through the quantum world

    CERN Document Server

    Fayngold, Moses

    2013-01-01

    Alongside a thorough definition of the basic concepts and their interrelations, backed by numerous examples, this textbook features a rare discussion of the quantum information theory. It also deals with other important topics hardly found in the literature, including the Robertson-Schrodinger-relation, angle and angular momentum uncertainties, interaction-free measurements, and the limitations of the no-cloning theorem With its interpretations of quantum mechanics and its discussions of quantum computing, this book is poised to become the standard textbook for advanced undergraduate and beginning graduate quantum mechanics courses and as an essential reference for physics students and physics professionals.

  20. Equivalence principle and quantum mechanics: quantum simulation with entangled photons.

    Science.gov (United States)

    Longhi, S

    2018-01-15

    Einstein's equivalence principle (EP) states the complete physical equivalence of a gravitational field and corresponding inertial field in an accelerated reference frame. However, to what extent the EP remains valid in non-relativistic quantum mechanics is a controversial issue. To avoid violation of the EP, Bargmann's superselection rule forbids a coherent superposition of states with different masses. Here we suggest a quantum simulation of non-relativistic Schrödinger particle dynamics in non-inertial reference frames, which is based on the propagation of polarization-entangled photon pairs in curved and birefringent optical waveguides and Hong-Ou-Mandel quantum interference measurement. The photonic simulator can emulate superposition of mass states, which would lead to violation of the EP.

  1. Fermionic quantum mechanics and superfields

    International Nuclear Information System (INIS)

    Marnelius, R.

    1990-01-01

    The explicit forms of consistent eigenstate representations for finite dimensional fermionic quantum theories are considered in detail. In particular are the possible Grassmann characters of the eigenstates determined. A straightforward Schrodinger representation is shown to exist if they are even or odd. For an odd number of real eigenvalues, the eigenstates cannot be even or odd. Still a consistent Schrodinger picture is shown to exist provided the basic canonical operators are antilinearly represented. Since the wave functions within the Schrodinger picture are super-fields, the class of superfields which also are first quantized wave functions is determined

  2. Insights into Teaching Quantum Mechanics in Secondary and Lower Undergraduate Education

    Science.gov (United States)

    Krijtenburg-Lewerissa, K.; Pol, H. J.; Brinkman, A.; van Joolingen, W. R.

    2017-01-01

    This study presents a review of the current state of research on teaching quantum mechanics in secondary and lower undergraduate education. A conceptual approach to quantum mechanics is being implemented in more and more introductory physics courses around the world. Because of the differences between the conceptual nature of quantum mechanics and…

  3. The cellular automaton interpretation of quantum mechanics

    CERN Document Server

    't Hooft, Gerard

    2016-01-01

    This book presents the deterministic view of quantum mechanics developed by Nobel Laureate Gerard 't Hooft. Dissatisfied with the uncomfortable gaps in the way conventional quantum mechanics meshes with the classical world, 't Hooft has revived the old hidden variable ideas, but now in a much more systematic way than usual. In this, quantum mechanics is viewed as a tool rather than a theory. The book presents examples of models that are classical in essence, but can be analysed by the use of quantum techniques, and argues that even the Standard Model, together with gravitational interactions, might be viewed as a quantum mechanical approach to analysing a system that could be classical at its core. He shows how this approach, even though it is based on hidden variables, can be plausibly reconciled with Bell's theorem, and how the usual objections voiced against the idea of ‘superdeterminism' can be overcome, at least in principle. This framework elegantly explains - and automatically cures - the problems of...

  4. Quantum mechanics on the personal computer

    International Nuclear Information System (INIS)

    Brandt, S.; Dahmen, H.D.

    1989-01-01

    'Quantum Mechanics on the PC' presents the most up-to-date access to elementary quantum mechanics. Based on the interactive program Interquanta (included on a 5 1/4'' Floppy Disk, MS-DOS) and its extensive 3D colour graphic features, the book guides its readers through computer experiments on - free particles and wave packets - bound states in various potentials - coherent and squeezed states in time-dependent motion - scattering and resonances - analogies in optics - quantized angular momentum - distinguishable and indistinguishable particles - special functions of mathematical physics. The course with a wide variety of more than 250 detailed, class-tested problems provides students with a unique practical experience of complex probability amplitudes, eigenvalues, scattering cross sections and the like. Lecturers and teachers will find excellent, hands-on classroom demonstrations for their quantum mechanics course. (orig.)

  5. Double stochastic matrices in quantum mechanics

    International Nuclear Information System (INIS)

    Louck, J.D.

    1997-01-01

    The general set of doubly stochastic matrices of order n corresponding to ordinary nonrelativistic quantum mechanical transition probability matrices is given. Lande's discussion of the nonquantal origin of such matrices is noted. Several concrete examples are presented for elementary and composite angular momentum systems with the focus on the unitary symmetry associated with such systems in the spirit of the recent work of Bohr and Ulfbeck. Birkhoff's theorem on doubly stochastic matrices of order n is reformulated in a geometrical language suitable for application to the subset of quantum mechanical doubly stochastic matrices. Specifically, it is shown that the set of points on the unit sphere in cartesian n'-space is subjective with the set of doubly stochastic matrices of order n. The question is raised, but not answered, as to what is the subset of points of this unit sphere that correspond to the quantum mechanical transition probability matrices, and what is the symmetry group of this subset of matrices

  6. Quantum mechanics and the physical reality concept

    International Nuclear Information System (INIS)

    von Borzeszkowski, H.H.; Wahsner, R.

    1988-01-01

    The difference between the measurement bases of classical and quantum mechanics is often interpreted as a loss of reality arising in quantum mechanics. In this paper it is shown that this apparent loss occurs only if one believes that refined everyday experience determines the Euclidean space as the real space, instead of considering this space, both in classical and quantum mechanics, as a theoretical construction needed for measurement and representing one part of a dualistic space conception. From this point of view, Einstein's program of a unified field theory can be interpreted as the attempt to find a physical theory that is less dualistic. However, if one regards this dualism as resulting from the requirements of measurements, one can hope for a weakening of the dualism but not expect to remove it completely

  7. A mathematical primer on quantum mechanics

    CERN Document Server

    Teta, Alessandro

    2018-01-01

    This book offers a rigorous yet elementary approach to quantum mechanics that will meet the needs of Master’s-level Mathematics students and is equally suitable for Physics students who are interested in gaining a deeper understanding of the mathematical structure of the theory. Throughout the coverage, which is limited to single-particle quantum mechanics, the focus is on formulating theory and developing applications in a mathematically precise manner. Following a review of selected key concepts in classical physics and the historical background, the basic elements of the theory of operators in Hilbert spaces are presented and used to formulate the rules of quantum mechanics. The discussion then turns to free particles, harmonic oscillators, delta potential, and hydrogen atoms, providing rigorous proofs of the corresponding dynamical properties. Starting from an analysis of these applications, readers are subsequently introduced to more advanced topics such as the classical limit, scattering theory, and s...

  8. Quantum Mechanical Study on the Structure and Vibrational Spectra of Cyclobutanone and 1,2-Cyclobutanedione

    Directory of Open Access Journals (Sweden)

    Anoop kumar Pandey

    2013-01-01

    Full Text Available For 1,2-cyclobutanedione and cyclobutanone, we have carried out a comparative study of different methods like B3LYP, LSDA, and B3PW91 of DFT using 6-31G (d, p basis set and MP2 method. On comparing these methods we find that B3PW91 method is closer to the experimental one. So by using B3PW91 method, we have made a comparative study of their structures, normal mode analysis, and other properties of the two derivatives of cyclobutane. The molecular HOMO, LUMO composition, their respective energy gaps, and MESP contours/surfaces have also been drawn to explain the activity of 1,2-cyclobutanedione and cyclobutanone.

  9. Reciprocal relativity of noninertial frames: quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Low, Stephen G [4301 Avenue D, Austin, Texas, 78751 (United States)

    2007-04-06

    Noninertial transformations on time-position-momentum-energy space {l_brace}t, q, p, e{r_brace} with invariant Born-Green metric ds{sup 2} = -dt{sup 2} + 1/c{sup 2} dq{sup 2} + 1/b{sup 2} (dp{sup 2} = 1/c{sup 2} de{sup 2}) and the symplectic metric -de and dt + dp and dq are studied. This U 1,3) group of transformations contains the Lorentz group as the inertial special case and, in the limit of small forces and velocities, reduces to the expected Hamilton transformations leaving invariant the symplectic metric and the nonrelativistic line element ds{sup 2} -dt{sup 2}. The U(1,3) transformations bound relative velocities by c and relative forces by b. Spacetime is no longer an invariant subspace but is relative to noninertial observer frames. In the limit of b {yields} {infinity}, spacetime is invariant. Born was lead to the metric by a concept of reciprocity between position and momentum degrees of freedom and for this reason we call this reciprocal relativity. For large b, such effects will almost certainly only manifest in a quantum regime. Wigner showed that special relativistic quantum mechanics follows from the projective representations of the inhomogeneous Lorentz group. Projective representations of a Lie group are equivalent to the unitary representations of its central extension. The same method of projective representations for the inhomogeneous U(1,3) group is used to define the quantum theory in the noninertial case. The central extension of the inhomogeneous U(1,3) group is the cover of the quaplectic group Q(1,3) U(1,3) x{sub s} H(4), H(4) is the Weyl-Heisenberg group. The H(4) group, and the associated Heisenberg commutation relations central to quantum mechanics, results directly from requiring projective representations. A set of second-order wave equations result from the representations of the Casimir operators.

  10. Exploring the High-Pressure Behavior of PETN: A Combined Quantum Mechanical and Experimental Study

    Science.gov (United States)

    2006-11-01

    calculations to explore the hypothesized compression-induced polymorphic phase transition [Gruzdkov 2004]. The initial crystal in these Figure 4...Scuseria, G.E., and Chabalowski, C.F. 2004: An ab Initio Study of Solid Nitromethane, HMX , RDX , and CL20: Successes and Failures of DFT. J. Phys. Chem... RDX , HMX , HNIW, and PETN Crystals. J. Phys. Chem. B, 103, 6783. Trotter, J., 1963: Bond lengths and angles in Pentaerythritol Tetranitrate. Acta

  11. A comparative study of iterative solutions to linear systems arising in quantum mechanics

    International Nuclear Information System (INIS)

    Jing Yanfei; Huang Tingzhu; Duan Yong; Carpentieri, Bruno

    2010-01-01

    This study is mainly focused on iterative solutions with simple diagonal preconditioning to two complex-valued nonsymmetric systems of linear equations arising from a computational chemistry model problem proposed by Sherry Li of NERSC. Numerical experiments show the feasibility of iterative methods to some extent when applied to the problems and reveal the competitiveness of our recently proposed Lanczos biconjugate A-orthonormalization methods to other classic and popular iterative methods. By the way, experiment results also indicate that application specific preconditioners may be mandatory and required for accelerating convergence.

  12. Random path formulation of nonrelativistic quantum mechanics

    International Nuclear Information System (INIS)

    Roncadelli, M.

    1993-01-01

    Quantum amplitudes satisfy (almost) the same calculus that probabilities obey in the theory of classical stochastic diffusion processes. As a consequence of this structural analogy, a new formulation of (nonrelativistic) quantum mechanics naturally arises as the quantum counterpart of the Langevin description of (classical) stochastic diffusion processes. Quantum fluctuations are simulated here by a Fresnel white noise (FWN), which is a (real) white noise with imaginary diffusion constant, whose functional (pseudo) measure yields the amplitude distribution for its configurations. Central to this approach is the idea that classical dynamical trajectories in configuration space are perturbed by the FWN. Hence, a single (arbitrary) classical dynamical path gets replaced by a family of quantum random paths (QRPs) - one for each FWN sample - all originating from the same space-time point (x', t'). The QRPs are the basic objects of the present formulation and are given by a Langevin equation with the FWN, whose drift is controlled by a (arbitrary) solution to the classical Hamilton-Jacobi equation. So, our approach is manifestly based on classical dynamics. Now, a transition amplitude is associated with each QRP: it gives the amplitude that a particle starting from (x', t') will reach (x'', t'') by travelling just along the considered QRP. The quantum mechanical propagator (x'', t'' modul x', t') then emerges as the FWN average of the transition amplitude along a QRP. Thus, quantum mechanics looks like classical mechanics as perturbed by the FWN. The general structure of this formulation is discussed in detail, along with some practical and conceptual implications. (author). 14 refs

  13. Mind, matter and quantum mechanics. 3. ed.

    International Nuclear Information System (INIS)

    Stapp, Henry P.

    2009-01-01

    ''Scientists other than quantum physicists often fail to comprehend the enormity of the conceptual change wrought by quantum theory in our basic conception of the nature of matter,'' writes Henry Stapp. Stapp is a leading quantum physicist who has given particularly careful thought to the implications of the theory that lies at the heart of modern physics. In this book, which contains several of his key papers as well as new material, he focuses on the problem of consciousness and explains how quantum mechanics allows causally effective conscious thought to be combined in a natural way with the physical brain made of neurons and atoms. The book is divided into four sections. The first consists of an extended introduction. Key foundational and somewhat more technical papers are included in the second part, together with a clear exposition of the ''orthodox'' interpretation of quantum mechanics. The third part addresses, in a non-technical fashion, the implications of the theory for some of the most profound questions that mankind has contemplated: How does the world come to be just what it is and not something else? How should humans view themselves in a quantum universe? What will be the impact on society of the revised scientific image of the nature of man? The final part contains a mathematical appendix for the specialist and a glossary of important terms and ideas for the interested layman. This third edition has been significantly expanded with two new chapters covering the author's most recent work. (orig.)

  14. Quantum mechanical studies of heavy ion scattering processes. Progress report, July 15, 1983-March, 1984

    International Nuclear Information System (INIS)

    Heil, T.G.

    1984-01-01

    The research done under this contract should provide valuable contributions to our understanding of atomic collision processes. The essence of this project is the description of low energy atomic collision process using molecular states formed by the collision partners in the interaction region. Over the eight months that this contract has been in effect, significant progress has been made on both fundamental and applied levels. On the most basic level, we have recently developed a new diabatic representation of the scattering which has none of the defects associated with the most commonly used formulation of Smith. This may prove to be of great importance since a proper diabatic description is thought to be a more reasonable representation of the actual physical scattering process than the adiabatic description. It should be noted that there is a great deal of controversy surrounding the word proper but our new formulation satisfies most, if not all, criteria for diabatic states. In addition, we have carried out or initiated theoretical studies on a number of atomic scattering processes involving charge transfer reactions and proton-induced fine-structure transitions. Our calculations of differential scattering cross sections for low energy charge transfer reaction should be of particular importance. A number of experimental groups are now proposing to measure these cross sections which our calculations predict should have large, striking features. Such comparisons would provide valuable tests of the theory of low energy atomic collision processes on a more fundamental level than previous comparisons of the total cross sections

  15. On uncertainty relations in quantum mechanics

    International Nuclear Information System (INIS)

    Ignatovich, V.K.

    2004-01-01

    Uncertainty relations (UR) are shown to have nothing specific for quantum mechanics (QM), being the general property valid for the arbitrary function. A wave function of a particle simultaneously having a precisely defined position and momentum in QM is demonstrated. Interference on two slits in a screen is shown to exist in classical mechanics. A nonlinear classical system of equations replacing the QM Schroedinger equation is suggested. This approach is shown to have nothing in common with the Bohm mechanics

  16. Study of autoradiolytic processes in tritium labelled polymers by quantum mechanical methods

    International Nuclear Information System (INIS)

    Postolache, Cristian; Fugaru, Viorel

    1999-01-01

    Autoradiolysis is a decomposition process of radionuclide labelled compounds. The process is similar to radiolytic degradation and is due to the autoirradiation following the decay of radioactive elements chemically bound to labelled molecules. In this work, an evaluating model of autoradiolysis behavior of tritium labelled polymers is presented. Polymeric structures of relevance for radioluminescent source industry, namely: polyethyl, polyethyl-phenyl, polypropyl, polypropyl-phenyl siloxanes, hydrogenated (tritiated) polyacetylenes with 1,4-diphenylbutane, 1,4-diphenyl-2-butene and 1,4-diphenylbutadiene structures have been investigated. Modelling of autoradiolytic processes was carried out with HYPERCHEM 4 software and its CHEMPLUS extension. Internal and external primary effects have been analyzed. External primary effects (EPE) were assessed by a procedure used in the study of radiolytic processes of solid polymers. A three step model was proposed for the assessment of internal primary effects (IPE): (a) tritium atom decay inducing a cationic radical in the molecular structure; (b) geometric re-optimization of cationic radical; (c) electron capture from environment and rapid breaking of the chemical bond of LUMO orbital distribution zone. The analysis of autoradiolytic processes in labelled polysiloxanes makes clear the dominant degradation function of EPE. The presence of phenyl groups in the polymeric structure improves the stability to autoradiolysis. The most resistant structures are obtained in the case of ethyl(propyl) and phenyl radicals positioned at different Si atoms. The hydrogenated oligomeric phenylacetylene structures present a high stability to autoradiolysis. In these cases, IPE in benzilic position have a major destructive function in the autoradiolytic process. (authors)

  17. Platinum adsorption onto graphene and oxidized graphene: A quantum mechanics study

    Energy Technology Data Exchange (ETDEWEB)

    Jafari, S.A.; Jahanshahi, M. [Nanotechnology Research Institute, School of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of); Ahangari, M. Ghorbanzadeh, E-mail: ghorbanzadeh.morteza@gmail.com [Department of Mechanical Engineering, Faculty of Engineering and Technology, University of Mazandaran, Babolsar (Iran, Islamic Republic of)

    2017-04-01

    Density functional theory based on first-principle calculations was used to examine platinum-supported oxidized graphene as a beneficial nanomaterial in terms of its catalytic activity and utility for contaminant removal and disinfecting polluted solutions in both domestic and industrial applications. The first step was to select the most appropriate available computing package to apply the supercell technique, which would provide a better representation of a large and real graphene slab. Using OpenMX was less time-consuming after we enforced a basis set for valence electrons to avoid an all-electron calculation, and this had very slight and negligible effect on the accuracy of the calculations. The OpenMX software was selected to perform forward steps of investigating changes in the properties such as adsorption energy and ground state structure of the complexes made by the adsorption of a platinum atom on the surface of pristine graphene (Pt/PG) and oxidized graphene (Pt/OG), which had the lowest adsorption energy of −5.28 eV. Moreover, we examined the effect of Pt atom adsorption on the surface and between two layers of graphene. Our results show that, there was no specific change observed in mentioned properties of Pt atom adsorption on bilayer graphene in comparison with single layer. - Highlights: • Pt adsorption on graphene and oxidized graphene was examined. • We have also considered the effect of the layered graphene on the Pt adsorption. • We first compared two different DFT calculation codes, SIESTA and OpenMX. • We then used ORCA to validate and select a suitable computation package for this study.

  18. Can quantum mechanics be an emergent phenomenon?

    Science.gov (United States)

    Blasone, Massimo; Jizba, Petr; Scardigli, Fabio

    2009-06-01

    We raise the issue whether conventional quantum mechanics, which is not a hidden variable theory in the usual Jauch-Piron's sense, might nevertheless be a hidden variable theory in the sense recently conjectured by G. 't Hooft in his pre-quantization scheme. We find that quantum mechanics might indeed have a fully deterministic underpinning by showing that Born's rule naturally emerges (i.e., it is not postulated) when 't Hooft's Hamiltonian for be-ables is combined with Koopmann-von Neumann operatorial formulation of classical physics.

  19. Can quantum mechanics be an emergent phenomenon?

    Energy Technology Data Exchange (ETDEWEB)

    Blasone, Massimo [INFN, Gruppo Collegato di Salerno, DMI, Universita di Salerno, Fisciano - 84084 (Italy); Jizba, Petr [ITP, Freie Universitaet Berlin, Arnimallee 14 D-14195 Berlin (Germany); Scardigli, Fabio, E-mail: blasone@sa.infn.i, E-mail: jizba@physik.fu-berlin.d, E-mail: fabio@phys.ntu.edu.t [Leung Center for Cosmology and Particle Astrophysics (LeCosPA), Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

    2009-06-01

    We raise the issue whether conventional quantum mechanics, which is not a hidden variable theory in the usual Jauch-Piron's sense, might nevertheless be a hidden variable theory in the sense recently conjectured by G. 't Hooft in his pre-quantization scheme. We find that quantum mechanics might indeed have a fully deterministic underpinning by showing that Born's rule naturally emerges (i.e., it is not postulated) when 't Hooft's Hamiltonian for be-ables is combined with Koopmann-von Neumann operatorial formulation of classical physics.

  20. Can quantum mechanics be an emergent phenomenon?

    International Nuclear Information System (INIS)

    Blasone, Massimo; Jizba, Petr; Scardigli, Fabio

    2009-01-01

    We raise the issue whether conventional quantum mechanics, which is not a hidden variable theory in the usual Jauch-Piron's sense, might nevertheless be a hidden variable theory in the sense recently conjectured by G. 't Hooft in his pre-quantization scheme. We find that quantum mechanics might indeed have a fully deterministic underpinning by showing that Born's rule naturally emerges (i.e., it is not postulated) when 't Hooft's Hamiltonian for be-ables is combined with Koopmann-von Neumann operatorial formulation of classical physics.

  1. Quantum mechanical facets of chemical bonds

    International Nuclear Information System (INIS)

    Daudel, R.

    1976-01-01

    To define the concept of bond is both a central problem of quantum chemistry and a difficult one. The concept of bond appeared little by little in the mind of chemists from empirical observations. From the wave-mechanical viewpoint it is not an observable. Therefore there is no precise operator associated with that concept. As a consequence there is not a unique approach to the idea of chemical bond. This is why it is preferred to present various quantum mechanical facets, e.g. the energetic facet, the density facet, the partitioning facet and the functional facet, of that important concept. (Auth.)

  2. Multiple-event probability in general-relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Hellmann, Frank; Mondragon, Mauricio; Perez, Alejandro; Rovelli, Carlo

    2007-01-01

    We discuss the definition of quantum probability in the context of 'timeless' general-relativistic quantum mechanics. In particular, we study the probability of sequences of events, or multievent probability. In conventional quantum mechanics this can be obtained by means of the 'wave function collapse' algorithm. We first point out certain difficulties of some natural definitions of multievent probability, including the conditional probability widely considered in the literature. We then observe that multievent probability can be reduced to single-event probability, by taking into account the quantum nature of the measuring apparatus. In fact, by exploiting the von-Neumann freedom of moving the quantum/classical boundary, one can always trade a sequence of noncommuting quantum measurements at different times, with an ensemble of simultaneous commuting measurements on the joint system+apparatus system. This observation permits a formulation of quantum theory based only on single-event probability, where the results of the wave function collapse algorithm can nevertheless be recovered. The discussion also bears on the nature of the quantum collapse

  3. On time in quantum mechanics

    International Nuclear Information System (INIS)

    Vona, Nicola

    2014-01-01

    Although time measurements are routinely performed in laboratories, their theoretical description is still an open problem. Similarly, also the validity and the status of the energy-time uncertainty relation is unsettled. In the first part of this work the necessity of positive operator valued measures (POVM) as descriptions of every quantum experiment is reviewed, as well as the suggestive role played by the probability current in time measurements. Furthermore, it is shown that no POVM exists, which approximately agrees with the probability current on a very natural set of wave functions; nevertheless, the choice of the set is crucial, and on more restrictive sets the probability current does provide a good arrival time prediction. Some ideas to experimentally detect quantum effects in time measurements are discussed. In the second part of the work the energy-time uncertainty relation is considered, in particular for a model of alpha decay for which the variance of the energy can be calculated explicitly, and the variance of time can be estimated. This estimate is tight for systems with long lifetimes, in which case the uncertainty relation is shown to be satisfied. Also the linewidth-lifetime relation is shown to hold, but contrary to the common expectation, it is found that the two relations behave independently, and therefore it is not possible to interpret one as a consequence of the other. To perform the mentioned analysis quantitative scattering estimates are necessary. To this end, bounds of the form parallel 1 R e -iHt ψ parallel (2)/(2)≤Ct -3 have been derived, where ψ denotes the initial state, H the Hamiltonian, R a positive constant, and C is explicitly known. As intermediate step, bounds on the derivatives of the S-matrix in the form parallel 1 K S (n) parallel ∞ ≤C n,K have been established, with n=1,2,3, and the constants C n,K explicitly known.

  4. What is Quantum Mechanics? A Minimal Formulation

    Science.gov (United States)

    Friedberg, R.; Hohenberg, P. C.

    2018-03-01

    This paper presents a minimal formulation of nonrelativistic quantum mechanics, by which is meant a formulation which describes the theory in a succinct, self-contained, clear, unambiguous and of course correct manner. The bulk of the presentation is the so-called "microscopic theory", applicable to any closed system S of arbitrary size N, using concepts referring to S alone, without resort to external apparatus or external agents. An example of a similar minimal microscopic theory is the standard formulation of classical mechanics, which serves as the template for a minimal quantum theory. The only substantive assumption required is the replacement of the classical Euclidean phase space by Hilbert space in the quantum case, with the attendant all-important phenomenon of quantum incompatibility. Two fundamental theorems of Hilbert space, the Kochen-Specker-Bell theorem and Gleason's theorem, then lead inevitably to the well-known Born probability rule. For both classical and quantum mechanics, questions of physical implementation and experimental verification of the predictions of the theories are the domain of the macroscopic theory, which is argued to be a special case or application of the more general microscopic theory.

  5. Quantum mechanics formalism for biological evolution

    International Nuclear Information System (INIS)

    Bianconi, Ginestra; Rahmede, Christoph

    2012-01-01

    Highlights: ► Biological evolution is an off-equilibrium process described by path integrals over phylogenies. ► The phylogenies are sums of linear lineages for asexual populations. ► For sexual populations, each lineage is a tree and the path integral is given by a sum over these trees. ► Quantum statistics describe the stationary state of biological populations in simple cases. - Abstract: We study the evolution of sexual and asexual populations in fitness landscapes compatible with epistatic interactions. We find intriguing relations between the mathematics of biological evolution and quantum mechanics formalism. We give the general structure of the evolution of sexual and asexual populations which is in general an off-equilibrium process that can be expressed by path integrals over phylogenies. These phylogenies are the sum of linear lineages for asexual populations. For sexual populations, instead, each lineage is a tree of branching ratio two and the path integral describing the evolving population is given by a sum over these trees. Finally we show that the Bose–Einstein and the Fermi–Dirac distributions describe the stationary state of biological populations in simple cases.

  6. Single trapped cold ions: a testing ground for quantum mechanics

    International Nuclear Information System (INIS)

    Maniscalco, S

    2005-01-01

    In this article I review some results obtained during my PhD work in the group of Professor Messina, at the University of Palermo. I discuss some proposals aimed at exploring fundamental issues of quantum theory, e.g. entanglement and quantum superpositions, in the context of single trapped ions. This physical context turns out to be extremely well suited both for studying fundamental features of quantum mechanics, such as the quantum-classical border, and for technological applications such as quantum logic gates and quantum registers. I focus on some procedures for engineering nonclassical states of the vibrational motion of the centre of mass of the ion. I consider both the case in which the ion interacts with classical laser beams and the case of interaction with a quantized mode of light. In particular, I discuss the generation of Schroedinger cat-like states, Bell states and Greenberger-Horn-Zeilinger states. The schemes for generating nonclassical states stem from two different quantum processes: the parity effect and the quantum state manipulation via quantum non-demolition measurement. Finally, I consider a microscopic theory of the interaction of a quantum harmonic oscillator (the centre of mass of the ion in the trapped ion context) with a bosonic thermal environment. Using an exact approach to the dynamics, I discuss a quantum theory of heating of trapped ions able to describe both the short time non-Markovian regime and the thermalization process. I conclude showing briefly how the trapped ion systems can be used as simulators of key models of open quantum systems such as the Caldeira-Leggett model. (phd tutorial)

  7. The pursuit of locality in quantum mechanics

    Science.gov (United States)

    Hodkin, Malcolm

    The rampant success of quantum theory is the result of applications of the 'new' quantum mechanics of Schrodinger and Heisenberg (1926-7), the Feynman-Schwinger-Tomonaga Quantum Electro-dynamics (1946-51), the electro-weak theory of Salaam, Weinberg, and Glashow (1967-9), and Quantum Chromodynamics (1973-); in fact, this success of 'the' quantum theory has depended on a continuous stream of brilliant and quite disparate mathematical formulations. In this carefully concealed ferment there lie plenty of unresolved difficulties, simply because in churning out fabulously accurate calculational tools there has been no sensible explanation of all that is going on. It is even argued that such an understanding is nothing to do with physics. A long-standing and famous illustration of this is the paradoxical thought-experiment of Einstein, Podolsky and Rosen (1935). Fundamental to all quantum theories, and also their paradoxes, is the location of sub-microscopic objects; or, rather, that the specification of such a location is fraught with mathematical inconsistency. This project encompasses a detailed, critical survey of the tangled history of Position within quantum theories. The first step is to show that, contrary to appearances, canonical quantum mechanics has only a vague notion of locality. After analysing a number of previous attempts at a 'relativistic quantum mechanics', two lines of thought are considered in detail. The first is the work of Wan and students, which is shown to be no real improvement on the iisu.al 'nonrelativistic' theory. The second is based on an idea of Dirac's - using backwards-in-time light-cones as the hypersurface in space-time. There remain considerable difficulties in the way of producing a consistent scheme here. To keep things nicely stirred up, the author then proposes his own approach - an adaptation of Feynman's QED propagators. This new approach is distinguished from Feynman's since the propagator or Green's function is not obtained

  8. Foundations of a spacetime path formalism for relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Seidewitz, Ed

    2006-01-01

    Quantum field theory is the traditional solution to the problems inherent in melding quantum mechanics with special relativity. However, it has also long been known that an alternative first-quantized formulation can be given for relativistic quantum mechanics, based on the parametrized paths of particles in spacetime. Because time is treated similarly to the three space coordinates, rather than as an evolution parameter, such a spacetime approach has proved particularly useful in the study of quantum gravity and cosmology. This paper shows how a spacetime path formalism can be considered to arise naturally from the fundamental principles of the Born probability rule, superposition, and Poincare invariance. The resulting formalism can be seen as a foundation for a number of previous parametrized approaches in the literature, relating, in particular, 'off-shell' theories to traditional on-shell quantum field theory. It reproduces the results of perturbative quantum field theory for free and interacting particles, but provides intriguing possibilities for a natural program for regularization and renormalization. Further, an important consequence of the formalism is that a clear probabilistic interpretation can be maintained throughout, with a natural reduction to nonrelativistic quantum mechanics

  9. Quantum mechanical calculations to chemical accuracy

    Science.gov (United States)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1991-01-01

    The accuracy of current molecular-structure calculations is illustrated with examples of quantum mechanical solutions for chemical problems. Two approaches are considered: (1) the coupled-cluster singles and doubles (CCSD) with a perturbational estimate of the contribution of connected triple excitations, or CCDS(T); and (2) the multireference configuration-interaction (MRCI) approach to the correlation problem. The MRCI approach gains greater applicability by means of size-extensive modifications such as the averaged-coupled pair functional approach. The examples of solutions to chemical problems include those for C-H bond energies, the vibrational frequencies of O3, identifying the ground state of Al2 and Si2, and the Lewis-Rayleigh afterglow and the Hermann IR system of N2. Accurate molecular-wave functions can be derived from a combination of basis-set saturation studies and full configuration-interaction calculations.

  10. Quantum-mechanical suppression of bremsstrahlung

    Energy Technology Data Exchange (ETDEWEB)

    Becker-Szendy, R.; Keller, L.; Niemi, G.; Perl, M.; Rochester, L. [Stanford Univ., CA (United States); Anthony, P. [Stanford Univ., CA (United States)]|[Lawrence Livermore National Lab., CA (United States); Bosted, P. [American Univ., Washington, DC (United States); Cavalli-Sforza, M.; Kelley, L.; Klein, S. [Univ. of California, Santa Cruz, CA (United States)] [and others

    1994-12-01

    The authors have studied quantum-mechanical suppression of bremsstrahlung of low-energy 1-500 MeV photons from high-energy 25 GeV electrons. They have measured the LPM effect, where multiple scattering of the radiating electron destroys coherence required for the emission of low-energy photons, and the dielectric effect, where the emitted photon traveling in the radiator medium interferes with itself. For the experiment, the collaboration developed a novel method of extracting a parasitic low-intensity high-energy electron beam into the fixed target area during normal SLC operation of the accelerator. The results agree quantitatively with Migdal`s calculation of the LPM effect. Surface effects, for which there is no satisfactory theoretical prediction, are visible at low photon energies. For very thin targets, the suppression disappears, as expected. Preliminary results on dielectric suppression of bremsstrahlung are in qualitative agreement with the expectation.

  11. A game with geometry and quantum mechanics

    International Nuclear Information System (INIS)

    Caianiello, E.R.

    1981-01-01

    An attempt is made to geometrize quantum mechanics. A hermitian metric has been taken as a dogma. The Heisenberg commutation relations in cartesian coordinates were taken for the single particle. Position and momentum operators become covariant derivatives, whose commutator is the curvature tensor. The Bohz-Sommerfeld rules are derived both for rotation and vibration degrees of freedom. The Klein-Gordon equation is determined by the first Beltrami parameters. The Dirac equation splits into two sets coupling 8-component semispinors of first and second kind. The only invariance allowed is found to be CPT. A study of the solutions of the Klein-Gordon equation shows that the free particle described by this formalism has inner degrees of freedom [ru

  12. Quantum mechanical/molecular mechanical and docking study of the novel analogues based on hybridization of common pharmacophores as potential anti-breast cancer agents.

    Science.gov (United States)

    Asadi, Parvin; Khodarahmi, Ghadamali; Farrokhpour, Hossein; Hassanzadeh, Farshid; Saghaei, Lotfollah

    2017-06-01

    In an attempt to identify some new potential leads as anti-breast cancer agents, novel hybrid compounds were designed by molecular hybridization approach. These derivatives were structurally derived from hybrid benzofuran-imidazole and quinazolinone derivatives, which had shown good cytotoxicity against the breast cancer cell line (MCF-7). Since aromatase enzyme (CYP19) is highly expressed in the MCF-7 cell line, the binding of these novel hybrid compounds to aromatase was investigated using the docking method. In this study, due to the positive charge on the imidazole ring of the designed ligands and also, the presence of heme iron in the active site of the enzyme, it was decided to optimize the ligand inside the protein to obtain more realistic atomic charges for it. Quantum mechanical/molecular mechanical (QM/MM) method was used to obtain more accurate atomic charges of ligand for docking calculations by considering the polarization effects of CYP19 on ligands. It was observed that the refitted charge improved the binding energy of the docked compounds. Also, the results showed that these novel hybrid compounds were adopted properly within the aromatase binding site, thereby suggesting that they could be potential inhibitors of aromatase. The main binding modes in these complexes were through hydrophobic and H bond interactions showing agreement with the basic physicochemical features of known anti aromatase compounds. Finally, the complex structures obtained from the docking study were used for single point QM/MM calculations to obtain more accurate electronic interaction energy, considering the electronic polarization of the ligand by its protein environment.

  13. Practical quantum mechanics modern tools and applications

    CERN Document Server

    Manousakis, Efstratios

    2016-01-01

    Quantum mechanics forms the foundation of all modern physics, including atomic, nuclear, and molecular physics, the physics of the elementary particles, condensed matter physics. Modern astrophysics also relies heavily on quantum mechanics. Quantum theory is needed to understand the basis for new materials, new devices, the nature of light coming from stars, the laws which govern the atomic nucleus, and the physics of biological systems. As a result the subject of this book is a required course for most physics graduate students. While there are many books on the subject, this book targets specifically graduate students and it is written with modern advances in various fields in mind. Many examples treated in the various chapters as well as the emphasis of the presentation in the book are designed from the perspective of such problems. For example, the book begins by putting the Schrodinger equation on a spatial discrete lattice and the continuum limit is also discussed, inspired by Hamiltonian lattice gauge ...

  14. Quantum mechanics study of repulsive π-π interaction and flexibility of phenyl moiety in the iron azodioxide complex

    Science.gov (United States)

    Liu, Yuemin; Liu, Yucheng; Murru, Siva; Tzeng, Nianfeng; Srivastava, Radhey S.

    2015-10-01

    In this study, repulsive π-π interactions within iron azodioxide complex Fe[Ph(O)NN(O)Ph]3 were quantum mechanically characterized using DFT, MP2 and CCSD(T) methods. Flexibility of six phenyl moieties in this complex structure was also investigated by structural optimization approach using the DFT methods. Our MP2 and CCSD(T) calculations of the closest pair provided interaction energy of 6.62 and 8.29 kcal/mol respectively, which indicate a strongest repulsion among these intra-molecular π-π interactions. Interaction energy of the particular π-π pair calculated from 24 hybrid DFT methods ranges from 4.56 kcal/mol from BHandH method to 15.15 kcal/mol from O3LYP method. Cares should be exercised when interpreting interaction energy and geometry optimization from DFT simulation of systems containing π-π interaction. Comparison between the DFT results and the benchmark CCSD(T) results shows that the DFT calculations of π-π interaction are reasonable but still need to be interpreted with caution. Furthermore, MP2 interaction energy of -44.69 kcal/mol between two substituted π systems/phenyl rings Ph(O)N-moieties suggested that above energetically unfavorable π-π interaction can be compensated by the covalent bond N-N in a single ligand Ph(O)NN(O)Ph, which allows for a reasonable stability across the complex molecules. Optimizations of the entire complex molecule using B3LYP and M06HF methods produced a large variation of π-π distances and orientations, which implied that the complex molecule may perform catalysis at room temperature.

  15. Emerging interpretations of quantum mechanics and recent progress in quantum measurement

    International Nuclear Information System (INIS)

    Clarke, M L

    2014-01-01

    The focus of this paper is to provide a brief discussion on the quantum measurement process, by reviewing select examples highlighting recent progress towards its understanding. The areas explored include an outline of the measurement problem, the standard interpretation of quantum mechanics, quantum to classical transition, types of measurement (including weak and projective measurements) and newly emerging interpretations of quantum mechanics (decoherence theory, objective reality, quantum Darwinism and quantum Bayesianism). (paper)

  16. Multiparticle quantum mechanics obeying fractional statistics

    International Nuclear Information System (INIS)

    Wu, Y.

    1984-01-01

    We obtain the rule governing many-body wave functions for particles obeying fractional statistics in two (space) dimensions. It generalizes and continuously interpolates the usual symmetrization and antisymmetrization. Quantum mechanics of more than two particles is discussed and some new features are found

  17. Quantum mechanics - a key to understanding magnetism

    International Nuclear Information System (INIS)

    Van Vleck, J.H.

    1978-01-01

    A translation is presented of J.H. van Vleck's lecture read at the 1977 Nobel Prize avarding ceremony. The basic results obtained using quantum mechanics in solving the problems of magnetism and especially paramagnetism are chronologically arranged. (Z.J.)

  18. Exceptional polynomials and SUSY quantum mechanics

    Indian Academy of Sciences (India)

    Abstract. We show that for the quantum mechanical problem which admit classical Laguerre/. Jacobi polynomials as solutions for the Schrödinger equations (SE), will also admit exceptional. Laguerre/Jacobi polynomials as solutions having the same eigenvalues but with the ground state missing after a modification of the ...

  19. Higher dimensional supersymmetric quantum mechanics and Dirac ...

    Indian Academy of Sciences (India)

    We exhibit the supersymmetric quantum mechanical structure of the full 3+1 dimensional Dirac equation considering `mass' as a function of coordinates. Its usefulness in solving potential problems is discussed with specific examples. We also discuss the `physical' significance of the supersymmetric states in this formalism.

  20. Science Academies' Refresher Course on Quantum Mechanics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 21; Issue 7. Science Academies' Refresher Course on Quantum Mechanics. Information and Announcements Volume 21 Issue 7 July 2016 pp 669-670. Fulltext. Click here to view fulltext PDF. Permanent link:

  1. A new exact quantum mechanical propagator

    NARCIS (Netherlands)

    Wiegel, F.W.; van Andel, P.W.

    1987-01-01

    The authors derive a closed-form expression for the time-dependent propagator for a quantum mechanical particle which is subject to an external force which is the sum of (i) a reflecting half-plane barrier with a straight edge, and (ii) a harmonic force pointing towards a point of the edge. This new

  2. Experiments in PT-symmetric quantum mechanics

    Czech Academy of Sciences Publication Activity Database

    Znojil, Miloslav

    2004-01-01

    Roč. 54, č. 1 (2004), s. 151-156 ISSN 0011-4626 R&D Projects: GA AV ČR IAA1048302 Institutional research plan: CEZ:AV0Z1048901 Keywords : quantum mechanics * relativistic kinematics * non-Hermitian observables Subject RIV: BE - Theoretical Physics Impact factor: 0.292, year: 2004

  3. Functional integral in supersymmetric quantum mechanics

    International Nuclear Information System (INIS)

    Ktitarev, D.V.

    1990-01-01

    The solution of the square root of the Schroedinger equation for the supersymmetric quantum mechanics is expressed in the form of series. The formula may be considered as a functional integral of the chronological exponent of the super-pseudodifferential operator symbol over the superspace. 10 refs

  4. Improving the gaussian effective potential: quantum mechanics

    International Nuclear Information System (INIS)

    Eboli, O.J.P.; Thomaz, M.T.; Lemos, N.A.

    1990-08-01

    In order to gain intuition for variational problems in field theory, we analyze variationally the quantum-mechanical anharmonic oscillator [(V(x)sup(k) - sub(2) x sup(2) + sup(λ) - sub(4) λ sup(4)]. Special attention is paid to improvements to the Gaussian effective potential. (author)

  5. On total noncommutativity in quantum mechanics

    Science.gov (United States)

    Lahti, Pekka J.; Ylinen, Kari

    1987-11-01

    It is shown within the Hilbert space formulation of quantum mechanics that the total noncommutativity of any two physical quantities is necessary for their satisfying the uncertainty relation or for their being complementary. The importance of these results is illustrated with the canonically conjugate position and momentum of a free particle and of a particle closed in a box.

  6. Quantum mechanics is compatible with realism

    International Nuclear Information System (INIS)

    Burgos, M.E.

    1987-01-01

    A new paradox of quantum mechanics has recently been proposed by an author claiming that any attempt to inject realism in physical theory is bound to lead to inconsistencies. In this paper the author shows that the mentioned paradox is not such a one and that at present there are no reasons to reject realism

  7. Can quantum mechanics fool the cosmic censor?

    International Nuclear Information System (INIS)

    Matsas, G. E. A.; Silva, A. R. R. da; Richartz, M.; Saa, A.; Vanzella, D. A. T.

    2009-01-01

    We revisit the mechanism for violating the weak cosmic-censorship conjecture (WCCC) by overspinning a nearly-extreme charged black hole. The mechanism consists of an incoming massless neutral scalar particle, with low energy and large angular momentum, tunneling into the hole. We investigate the effect of the large angular momentum of the incoming particle on the background geometry and address recent claims that such a backreaction would invalidate the mechanism. We show that the large angular momentum of the incident particle does not constitute an obvious impediment to the success of the overspinning quantum mechanism, although the induced backreaction turns out to be essential to restoring the validity of the WCCC in the classical regime. These results seem to endorse the view that the 'cosmic censor' may be oblivious to processes involving quantum effects.

  8. Advances in quantum mechanics contemporary trends and open problems

    CERN Document Server

    Dell'Antonio, Gianfausto

    2017-01-01

    This volume collects recent contributions on the contemporary trends in the mathematics of quantum mechanics, and more specifically in mathematical problems arising in quantum many-body dynamics, quantum graph theory, cold atoms, unitary gases, with particular emphasis on the developments of the specific mathematical tools needed, including: linear and non-linear Schrödinger equations, topological invariants, non-commutative geometry, resonances and operator extension theory, among others. Most of contributors are international leading experts or respected young researchers in mathematical physics, PDE, and operator theory. All their material is the fruit of recent studies that have already become a reference in the community. Offering a unified perspective of the mathematics of quantum mechanics, it is a valuable resource for researchers in the field.

  9. Quantum mechanics as a natural generalization of classical statistical mechanics

    International Nuclear Information System (INIS)

    Xu Laizi; Qian Shangwu

    1994-01-01

    By comparison between equations of motion of geometrical optics (GO) and that of classical statistical mechanics (CSM), it is found that there should be an analogy between GO and CSM instead of GO and classical mechanics (CM). Furthermore, by comparison between the classical limit (CL) of quantum mechanics (QM) and CSM, the authors find that CL of QM is CSM not CM, hence they demonstrated that QM is a natural generalization of CSM instead of CM

  10. Interactive Quantum Mechanics Quantum Experiments on the Computer

    CERN Document Server

    Brandt, S; Dahmen, H.D

    2011-01-01

    Extra Materials available on extras.springer.com INTERACTIVE QUANTUM MECHANICS allows students to perform their own quantum-physics experiments on their computer, in vivid 3D color graphics. Topics covered include: •        harmonic waves and wave packets, •        free particles as well as bound states and scattering in various potentials in one and three dimensions (both stationary and time dependent), •        two-particle systems, coupled harmonic oscillators, •        distinguishable and indistinguishable particles, •        coherent and squeezed states in time-dependent motion, •        quantized angular momentum, •        spin and magnetic resonance, •        hybridization. For the present edition the physics scope has been widened appreciably. Moreover, INTERQUANTA can now produce user-defined movies of quantum-mechanical situations. Movies can be viewed directly and also be saved to be shown later in any browser. Sections on spec...

  11. Quantum mechanical coherence, resonance, and mind

    International Nuclear Information System (INIS)

    Stapp, H.P.

    1995-01-01

    Norbert Wiener and J.B.S. Haldane suggested during the early thirties that the profound changes in our conception of matter entailed by quantum theory opens the way for our thoughts, and other experiential or mind-like qualities, to play a role in nature that is causally interactive and effective, rather than purely epiphenomenal, as required by classical mechanics. The mathematical basis of this suggestion is described here, and it is then shown how, by giving mind this efficacious role in natural process, the classical character of our perceptions of the quantum universe can be seen to be a consequence of evolutionary pressures for the survival of the species

  12. Quantum mechanical coherence, resonance, and mind

    Energy Technology Data Exchange (ETDEWEB)

    Stapp, H.P.

    1995-03-26

    Norbert Wiener and J.B.S. Haldane suggested during the early thirties that the profound changes in our conception of matter entailed by quantum theory opens the way for our thoughts, and other experiential or mind-like qualities, to play a role in nature that is causally interactive and effective, rather than purely epiphenomenal, as required by classical mechanics. The mathematical basis of this suggestion is described here, and it is then shown how, by giving mind this efficacious role in natural process, the classical character of our perceptions of the quantum universe can be seen to be a consequence of evolutionary pressures for the survival of the species.

  13. De Broglie's causal interpretations of quantum mechanics

    International Nuclear Information System (INIS)

    Ben-Dov, Y.

    1989-01-01

    In this article we trace the history of de Broglie's two causal interpretations of quantum mechanics, namely the double solution and the pilot wave theories, at the two periods in which he developed them: 1924-27 and 1952 onwards. Examining the reasons for which he always preferred the first theory to the second, reasons that are mainly concerned with the question of the physical nature of the quantum wave function, we try to show the continuity and the coherence of his underlying vision

  14. Quantum mechanics. Textbook on theoretical physics III. 4. rev. ed.

    International Nuclear Information System (INIS)

    Fliessbach, T.

    2005-01-01

    This textbook present an intoduction to quantum mechanics, as it is offerred at the university in the cycle ''Theoretical Physics''. Special value has the author put on a well readable, understandable, and surveyable representation, so that the reader it can reproduce without larger difficulties. By the partition into chapters, which form separated course units, and the kind of the representation the book is also suited for bachelor curricula. The quantum mechanics are first introduced in the form of Schroedinge's wave mechanics. The fundamental relations of quantum mechanics and their interpretation are thereby explained by means of examples and first applications. In the following chapters the most important applications of the Schroedinger equation are studied, like the alpha decay, the scattering of a particle on a potential, and the hydrogen atom. Thereafter the abstract formulation of quantum mechanics (Hilbert space) is introduced in analogy to the known structure of the vector space. This formulation is then applied to concrete problems like the oscillator, tha angular momentum, and the spin. The most important approximation methods of quantum mechanics are then summarized. In the concluding part about many-particle systems the ideal Fermi gas is treated; simple applications of this model in atomic, solid-state, nuclear, ans astrophysics are discussed

  15. Symmetry aspects in emergent quantum mechanics

    Science.gov (United States)

    Elze, Hans-Thomas

    2009-06-01

    We discuss an explicit realization of the dissipative dynamics anticipated in the proof of 't Hooft's existence theorem, which states that 'For any quantum system there exists at least one deterministic model that reproduces all its dynamics after prequantization'. - There is an energy-parity symmetry hidden in the Liouville equation, which mimics the Kaplan-Sundrum protective symmetry for the cosmological constant. This symmetry may be broken by the coarse-graining inherent in physics at scales much larger than the Planck length. We correspondingly modify classical ensemble theory by incorporating dissipative fluctuations (information loss) - which are caused by discrete spacetime continually 'measuring' matter. In this way, aspects of quantum mechanics, such as the von Neumann equation, including a Lindblad term, arise dynamically and expectations of observables agree with the Born rule. However, the resulting quantum coherence is accompanied by an intrinsic decoherence and continuous localization mechanism. Our proposal leads towards a theory that is linear and local at the quantum mechanical level, but the relation to the underlying classical degrees of freedom is nonlocal.

  16. The emergent Copenhagen interpretation of quantum mechanics

    Science.gov (United States)

    Hollowood, Timothy J.

    2014-05-01

    We introduce a new and conceptually simple interpretation of quantum mechanics based on reduced density matrices of sub-systems from which the standard Copenhagen interpretation emerges as an effective description of macroscopically large systems. This interpretation describes a world in which definite measurement results are obtained with probabilities that reproduce the Born rule. Wave function collapse is seen to be a useful but fundamentally unnecessary piece of prudent book keeping which is only valid for macro-systems. The new interpretation lies in a class of modal interpretations in that it applies to quantum systems that interact with a much larger environment. However, we show that it does not suffer from the problems that have plagued similar modal interpretations like macroscopic superpositions and rapid flipping between macroscopically distinct states. We describe how the interpretation fits neatly together with fully quantum formulations of statistical mechanics and that a measurement process can be viewed as a process of ergodicity breaking analogous to a phase transition. The key feature of the new interpretation is that joint probabilities for the ergodic subsets of states of disjoint macro-systems only arise as emergent quantities. Finally we give an account of the EPR-Bohm thought experiment and show that the interpretation implies the violation of the Bell inequality characteristic of quantum mechanics but in a way that is rather novel. The final conclusion is that the Copenhagen interpretation gives a completely satisfactory phenomenology of macro-systems interacting with micro-systems.

  17. A mathematical theory for deterministic quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Hooft, Gerard ' t [Institute for Theoretical Physics, Utrecht University (Netherlands); Spinoza Institute, Postbox 80.195, 3508 TD Utrecht (Netherlands)

    2007-05-15

    Classical, i.e. deterministic theories underlying quantum mechanics are considered, and it is shown how an apparent quantum mechanical Hamiltonian can be defined in such theories, being the operator that generates evolution in time. It includes various types of interactions. An explanation must be found for the fact that, in the real world, this Hamiltonian is bounded from below. The mechanism that can produce exactly such a constraint is identified in this paper. It is the fact that not all classical data are registered in the quantum description. Large sets of values of these data are assumed to be indistinguishable, forming equivalence classes. It is argued that this should be attributed to information loss, such as what one might suspect to happen during the formation and annihilation of virtual black holes. The nature of the equivalence classes follows from the positivity of the Hamiltonian. Our world is assumed to consist of a very large number of subsystems that may be regarded as approximately independent, or weakly interacting with one another. As long as two (or more) sectors of our world are treated as being independent, they all must be demanded to be restricted to positive energy states only. What follows from these considerations is a unique definition of energy in the quantum system in terms of the periodicity of the limit cycles of the deterministic model.

  18. The emergent Copenhagen interpretation of quantum mechanics

    International Nuclear Information System (INIS)

    Hollowood, Timothy J

    2014-01-01

    We introduce a new and conceptually simple interpretation of quantum mechanics based on reduced density matrices of sub-systems from which the standard Copenhagen interpretation emerges as an effective description of macroscopically large systems. This interpretation describes a world in which definite measurement results are obtained with probabilities that reproduce the Born rule. Wave function collapse is seen to be a useful but fundamentally unnecessary piece of prudent book keeping which is only valid for macro-systems. The new interpretation lies in a class of modal interpretations in that it applies to quantum systems that interact with a much larger environment. However, we show that it does not suffer from the problems that have plagued similar modal interpretations like macroscopic superpositions and rapid flipping between macroscopically distinct states. We describe how the interpretation fits neatly together with fully quantum formulations of statistical mechanics and that a measurement process can be viewed as a process of ergodicity breaking analogous to a phase transition. The key feature of the new interpretation is that joint probabilities for the ergodic subsets of states of disjoint macro-systems only arise as emergent quantities. Finally we give an account of the EPR–Bohm thought experiment and show that the interpretation implies the violation of the Bell inequality characteristic of quantum mechanics but in a way that is rather novel. The final conclusion is that the Copenhagen interpretation gives a completely satisfactory phenomenology of macro-systems interacting with micro-systems. (paper)

  19. On quantum gravity and the many-worlds interpretation of quantum mechanics

    International Nuclear Information System (INIS)

    Smolin, L.

    1984-01-01

    The paper examines the interpretation of quantum mechanics and the quantum theory of gravity. Foundational problems in quantum gravity; the many-worlds interpretation of quantum mechanics; the role of observation in the many-worlds and in the minimal relative state interpretations; and advantages of the many-worlds interpretation; are all discussed. (U.K.)

  20. Mathematical sense-making in quantum mechanics: An initial peek

    Science.gov (United States)

    Dreyfus, Benjamin W.; Elby, Andrew; Gupta, Ayush; Sohr, Erin Ronayne

    2017-12-01

    Mathematical sense-making—looking for coherence between the structure of the mathematical formalism and causal or functional relations in the world—is a core component of physics expertise. Some physics education research studies have explored what mathematical sense-making looks like at the introductory physics level, while some historians and "science studies" have explored how expert physicists engage in it. What is largely missing, with a few exceptions, is theoretical and empirical work at the intermediate level—upper division physics students—especially when they are learning difficult new mathematical formalism. In this paper, we present analysis of a segment of video-recorded discussion between two students grappling with a quantum mechanics question to illustrate what mathematical sense-making can look like in quantum mechanics. We claim that mathematical sense-making is possible and productive for learning and problem solving in quantum mechanics. Mathematical sense-making in quantum mechanics is continuous in many ways with mathematical sense-making in introductory physics. However, in the context of quantum mechanics, the connections between formalism, intuitive conceptual schema, and the physical world become more compound (nested) and indirect. We illustrate these similarities and differences in part by proposing a new symbolic form, eigenvector eigenvalue, which is composed of multiple primitive symbolic forms.

  1. To a causal formulation of quantum mechanics

    International Nuclear Information System (INIS)

    Brody, T.A.; Cetto, A.M.; Pena, L. de la

    1979-01-01

    This paper consists of two parts. In the first one we analyze the elements that a theory of quantum mechanics (QM) must contain in order to provide a physical explanation of the most notable quantum features (random behaviour, wave-particle duality, discrete spectra). We conclude that the theory that possesses the qualitative elements required is stochastic electrodynamics (SED), according to which the quantum behavior of the electron arises from its interaction with the stochastic electromagnetic background fiel associated with the zero-point energy. In the second part we show that the postulates of SED are suitable for the construction of a theory of the motion of the electron from which QM may be derived as an approximate description; hence, the mathematical formalism of QM too is justified by SED. Thus, the present theory generalizes QM and moreover, provides an objective statistical interpretation of it. (author)

  2. Spacetime coarse grainings in nonrelativistic quantum mechanics

    International Nuclear Information System (INIS)

    Hartle, J.B.

    1991-01-01

    Sum-over-histories generalizations of nonrelativistic quantum mechanics are explored in which probabilities are predicted, not just for alternatives defined on spacelike surfaces, but for alternatives defined by the behavior of spacetime histories with respect to spacetime regions. Closed, nonrelativistic systems are discussed whose histories are paths in a given configuration space. The action and the initial quantum state are assumed fixed and given. A formulation of quantum mechanics is used which assigns probabilities to members of sets of alternative coarse-grained histories of the system, that is, to the individual classes of a partition of its paths into exhaustive and exclusive classes. Probabilities are assigned to those sets which decohere, that is, whose probabilities are consistent with the sum rules of probability theory. Coarse graining by the behavior of paths with respect to regions of spacetime is described. For example, given a single region, the set of all paths may be partitioned into those which never pass through the region and those which pass through the region at least once. A sum-over-histories decoherence functional is defined for sets of alternative histories coarse-grained by spacetime regions. Techniques for the definition and effective computation of the relevant sums over histories by operator-product formulas are described and illustrated by examples. Methods based on Euclidean stochastic processes are also discussed and illustrated. Models of decoherence and measurement for spacetime coarse grainings are described. Issues of causality are investigated. Such spacetime generalizations of nonrelativistic quantum mechanics may be useful models for a generalized quantum mechanics of spacetime geometry

  3. Simulation with quantum mechanics/molecular mechanics for drug discovery.

    Science.gov (United States)

    Barbault, Florent; Maurel, François

    2015-10-01

    Biological macromolecules, such as proteins or nucleic acids, are (still) molecules and thus they follow the same chemical rules that any simple molecule follows, even if their size generally renders accurate studies unhelpful. However, in the context of drug discovery, a detailed analysis of ligand association is required for understanding or predicting their interactions and hybrid quantum mechanics/molecular mechanics (QM/MM) computations are relevant tools to help elucidate this process. In this review, the authors explore the use of QM/MM for drug discovery. After a brief description of the molecular mechanics (MM) technique, the authors describe the subtractive and additive techniques for QM/MM computations. The authors then present several application cases in topics involved in drug discovery. QM/MM have been widely employed during the last decades to study chemical processes such as enzyme-inhibitor interactions. However, despite the enthusiasm around this area, plain MM simulations may be more meaningful than QM/MM. To obtain reliable results, the authors suggest fixing several keystone parameters according to the underlying chemistry of each studied system.

  4. Theoretical physics 6 quantum mechanics : basics

    CERN Document Server

    Nolting, Wolfgang

    2017-01-01

    This textbook offers a clear and comprehensive introduction to the basics of quantum mechanics, one of the core components of undergraduate physics courses. It follows on naturally from the previous volumes in this series, thus developing the physical understanding further on to quantized states. The first part of the book introduces wave equations while exploring the Schrödinger equation and the hydrogen atom. More complex themes are covered in the second part of the book, which describes the Dirac formulism of quantum mechanics. Ideally suited to undergraduate students with some grounding in classical mechanics and electrodynamics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful German editions, the eight volumes of this...

  5. On phase-space representations of quantum mechanics using

    Indian Academy of Sciences (India)

    space representations of quantum mechanics using Glauber coherent states. DIÓGENES CAMPOS. Research Article Volume 87 Issue 2 August ... Keywords. Phase-space quantum mechanics, coherent states, Husimi function, Wigner function ...

  6. An objective interpretation of Lagrangian quantum mechanics

    International Nuclear Information System (INIS)

    Roberts, K.V.

    1978-01-01

    Unlike classical mechanics, the Copenhagen interpretation of quantum mechanics does not provide an objective space-time picture of the actual history of a physical system. This paper suggests how the conceptual foundations of quantum mechanics can be reformulated, without changing the mathematical content of the theory or its detailed agreement with experiment and without introducing any hidden variables, in order to provide an objective, covariant, Lagrangian description of reality which is deterministic and time-symmetric on the microscopic scale. The basis of this description can be expressed either as an action functional or as a summation over Feynman diagrams or paths. The probability laws associated with the quantum-mechanical measurement process, and the asymmetry in time of the principles of macroscopic causality and of the laws of statistical mechanics, are interpreted as consequences of the particular boundary conditions that apply to the actual universe. The objective interpretation does not include the observer and the measurement process among the fundamental concepts of the theory, but it does not entail a revision of the ideas of determinism and of time, since in a Lagrangian theory both initial and final boundary conditions on the action functional are required. (author)

  7. Wilson loops, instantons and quantum mechanics

    International Nuclear Information System (INIS)

    Schiereck, Marc

    2014-05-01

    In this thesis we examine two different problems. The first is the computation of vacuum expectation values of Wilson loop operators in ABJM theory, the other problem is finding the instanton series of the refined topological string on certain local Calabi-Yau geometries in the Nekrasov-Shatashvili limit. Based on the description of ABJM theory as a matrix model, it is possible to find a description of it in terms of an ideal Fermi gas with a non-trivial one-particle Hamiltonian. The vacuum-expectation-values of Wilson loop operators in ABJM theory correspond to averages of operators in the statistical-mechanical problem. Using the WKB expansion, it is possible to extract the full 1/N expansion of the vevs, up to exponentially small contributions, for arbitrary Chern-Simons coupling. We compute these vevs for the 1/6 and 1/2 BPS Wilson loops at any winding number. These can be written in terms of the Airy function. The expressions we found reproduce the low genus results previously obtained in the 't Hooft expansion. In another problem we use mirror symmetry, quantum geometry and modularity properties of elliptic curves to calculate the refined free energies, given in terms of an instanton sum, in the Nekrasov-Shatashvili limit on non-compact toric Calabi-Yau manifolds, based on del Pezzo surfaces. Quantum geometry here is to be understood as a quantum deformed version of rigid special geometry, which has its origin in the quantum mechanical behavior of branes in the topological string B-model. We argue that in the Seiberg-Witten picture only the Coulomb parameters lead to quantum corrections, while the mass parameters remain uncorrected. In certain cases we also compute the expansion of the free energies at the orbifold point and the conifold locus. We compute the quantum corrections order by order on ℎ by deriving second order differential operators, which act on the classical periods.

  8. Hydrothermal synthesis of ZnSe:Cu quantum dots and their luminescent mechanism study by first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Qingshuang; Bai, Yijia; Han, Lin; Deng, Xiaolong [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Graduate School, Chinese Academy of Sciences, Beijing 10049 (China); Wu, Xiaojie [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang, Zhongchang [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Liu, Xiaojuan, E-mail: lxjuan@ciac.jl.cn [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng, Jian, E-mail: jmeng@ciac.jl.cn [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2013-11-15

    An one-pot synthesis of aqueous ZnSe:Cu nanocrystals (NCs) is realized in aqueous solution by a facile yet efficient hydrothermal technique. The dopant emission spectrum of the NCs is tunable, spanning a wide range from 438 to 543 nm. Room-temperature quantum yield for the NCs prepared at the optimal conditions reaches as high as 20% without any post-treatment. The ZnSe:Cu NCs prepared in a neutral aqueous solution (pH=8) are remarkably stable and exhibit comparatively high photoluminescent quantum yield (PL QY) as high as 17%. First-principles pseudopotential calculations using plane-wave basis functions have been performed. The formation energies of copper ions occupied in the interstitial octahedron and substitutional tetrahedral Zn{sup 2+} sites have been calculated. The occupation of copper ions in the interstitial octahedral site is found to be more thermodynamics-facilitated by −0.98 eV. The density of state analysis indicates that the Cu-related emission is primary dominated by the substitutional tetrahedral Cu ions, and the large dopant related emission width of ZnSe:Cu NCs originated from the corresponding Cu 3d impurity band. Highlights: • One-pot synthesis of aqueous ZnSe:Cu nanocrystals with tunable emission and high QY%. • ZnSe:Cu NCs exhibit high QY% at neutral pH suitable for biological application. • The microscopic mechanism underlying Cu-related emission has been provided.

  9. The birth and growth of quantum theory. From quantum hypothesis to quantum mechanics

    International Nuclear Information System (INIS)

    Peng Huanwu

    2001-01-01

    The short history covers the birth and early growth of quantum theory from 1900 to 1928, beginning with Planck's formula and the quantum hypothesis for the black-body radiation. After a description of the rise and decline of the old quantum theory in connection with its application in spectroscopy, two paths based on the rigorous formulation of the correspondence principle leading to matrix mechanics (1925) and Dirac's non-commuting q-numbers (1925) are explained. Another path based on the generalization of the wave-particle aspect of light quanta is then shown to lead to wave mechanics (1926). Among the works during the early growth of quantum mechanics in 1927-1928, representation theory, the uncertainty principle, two-electron problems, and Dirac's relativistic theory of electrons are discussed

  10. Applications of density matrix in the fractional quantum mechanics: Thomas-Fermi model and Hohenberg-Kohn theorems revisited

    International Nuclear Information System (INIS)

    Dong, Jianping

    2011-01-01

    The many-body space fractional quantum system is studied using the density matrix method. We give the new results of the Thomas-Fermi model, obtain the quantum pressure of the free electron gas. We also show the validity of the Hohenberg-Kohn theorems in the space fractional quantum mechanics and generalize the density functional theory to the fractional quantum mechanics. -- Highlights: → Thomas-Fermi model under the framework of fractional quantum mechanics is studied. → We show the validity of the HK theorems in the space fractional quantum mechanics. → The density functional theory is generalized to the fractional quantum mechanics.

  11. Quantum mechanics. Introduction. 6. rev. and enl. ed.

    International Nuclear Information System (INIS)

    Greiner, W.

    2005-01-01

    The following topics are dealt with: Quantization of physical quantities, radiation laws, the wave aspect of matter, mathematical foundations of quantum mechanics, ther Schroedinger equation, the harmonic oscillator, the transition from classical to quantum mechanics, a charged particle in the electromagnetic field, the hydrogen atom, perturbation theory and approximation procedures, spin, a nonrelativistic wave equation with spin, systems of identical particles, the formal scheme of quantum mechanics, conceptions and philosophical problems of quantum mechanics. (HSI)

  12. Positive Nonlinear Dynamical Group Uniting Quantum Mechanics and Thermodynamics

    OpenAIRE

    Beretta, Gian Paolo

    2006-01-01

    We discuss and motivate the form of the generator of a nonlinear quantum dynamical group 'designed' so as to accomplish a unification of quantum mechanics (QM) and thermodynamics. We call this nonrelativistic theory Quantum Thermodynamics (QT). Its conceptual foundations differ from those of (von Neumann) quantum statistical mechanics (QSM) and (Jaynes) quantum information theory (QIT), but for thermodynamic equilibrium (TE) states it reduces to the same mathematics, and for zero entropy stat...

  13. Computational methods to study the structure and dynamics of biomolecules and biomolecular processes from bioinformatics to molecular quantum mechanics

    CERN Document Server

    2014-01-01

    Since the second half of the 20th century machine computations have played a critical role in science and engineering. Computer-based techniques have become especially important in molecular biology, since they often represent the only viable way to gain insights into the behavior of a biological system as a whole. The complexity of biological systems, which usually needs to be analyzed on different time- and size-scales and with different levels of accuracy, requires the application of different approaches, ranging from comparative analysis of sequences and structural databases, to the analysis of networks of interdependence between cell components and processes, through coarse-grained modeling to atomically detailed simulations, and finally to molecular quantum mechanics. This book provides a comprehensive overview of modern computer-based techniques for computing the structure, properties and dynamics of biomolecules and biomolecular processes. The twenty-two chapters, written by scientists from all over t...

  14. Three-dimensional quantum mechanical studies of D+H2 → HD+H reactive scattering. II

    International Nuclear Information System (INIS)

    Choi, B.H.; Tang, K.T.

    1975-01-01

    Three-dimensional quantum mechanical calculations are carried out for the reactive scattering of D+H 2 →DH+H on the Yates--Lester potential surface. The differential and total cross sections as well as the S-matrix elements are obtained and are compared with the corresponding results obtained on the Porter--Karplus potential surface. The differential cross sections and the distributions over final angular momentum states are in much better agreement with the experimental measurements than the previous results obtained on the Porter--Karplus surface. However, the calculated threshold energy for the reaction seems too high whereas the threshold on the Porter--Karplus potential seems too low. These dynamic attributes are discussed in terms of the two-body potentials between the atom and the molecule

  15. Logical reformulation of quantum mechanics. I. Foundations

    International Nuclear Information System (INIS)

    Omnes, R.

    1988-01-01

    The basic rules of quantum mechanics are reformulated. They deal primarily with individual systems and do not assume that every ket may represent a physical state. The customary kinematic and dynamic rules then allow to construct consistent Boolean logics describing the history of a system, following essentially Griffiths' proposal. Logical implication is defined within these logics, the multiplicity of which reflects the complementary principle. Only one interpretive rule of quantum mechanics is necessary in such a framework. It states that these logics provide bona fide foundations for the description of a quantum system and for reasoning about it. One attempts to build up classical physics, including classical logic, on these quantum foundations. The resulting theory of measurement needs not to state a priori that the eigenvalues of an observable have to be the results of individual measurements nor to assume wave packet reduction. Both these properties can be obtained as consequences of the basic rules. One also needs not to postulate that every observable is measurable, even in principle. A proposition calculus is obtained, allowing in principle the replacement of the discussion of problems concerned with the practical interpretation of experiments by due calculations

  16. Irreversible processes in quantum mechanical systems

    International Nuclear Information System (INIS)

    Talkner, P.

    1979-01-01

    Although the information provided by the evolution of the density matrix of a quantum system is equivalent with the knowledge of all observables at a given time, it turns out ot be insufficient to answer certain questions in quantum optics or linear response theory where the commutator of certain observables at different space-time points is needed. In this doctoral thesis we prove the existence of density matrices for common probabilities at multiple times and discuss their properties and their characterization independent of a special representation. We start with a compilation of definitions and properties of classical common probabilities and correlation functions. In the second chapter we give the definition of a quantum mechanical Markov process and derive the properties of propagators, generators and conditional probabilities as well as their mutual relations. The third chapter is devoted to a treatment of quantum mechanical systems in thermal equilibrium for which the principle of detailed balance holds as a consequence of microreversibility. We work out the symmetry properties of the two-sided correlation functions which turn out to be analogous to those in classical processes. In the final chapter we use the Gaussian behavior of the stationary correlation function of an oscillator and determine a class of Markov processes which are characterized by dissipative Lionville operators. We succeed in obtaining the canonical representation in a purely algebraic way by means of similarity transformations. Starting from this representation it is particularly easy to calculate the propagator and the correlation function. (HJ) 891 HJ/HJ 892 MKO

  17. A relational solution to the problem of time in quantum mechanics and quantum gravity: a fundamental mechanism for quantum decoherence

    International Nuclear Information System (INIS)

    Gambini, Rodolfo; Porto, Rafael A; Pullin, Jorge

    2004-01-01

    The use of a relational time in quantum mechanics is a framework in which one promotes to quantum operators all variables in a system, and later chooses one of the variables to operate like a 'clock'. Conditional probabilities are computed for variables of the system to take certain values when the 'clock' specifies a certain time. This framework is attractive in contexts where the assumption of usual quantum mechanics of the existence of an external, perfectly classical clock, appears unnatural, as in quantum cosmology. Until recently, there were problems with such constructions in ordinary quantum mechanics with additional difficulties in the context of constrained theories like general relativity. A scheme we recently introduced to consistently discretize general relativity removed such obstacles. Since the clock is now an object subject to quantum fluctuations, the resulting evolution in time is not exactly unitary and pure states decohere into mixed states. Here we work out in detail the type of decoherence generated, and we find it to be of Lindblad type. This is attractive since it implies that one can have loss of coherence without violating the conservation of energy. We apply the framework to a simple cosmological model to illustrate how a quantitative estimate of the effect could be computed. For most quantum systems it appears to be too small to be observed, although certain macroscopic quantum systems could in the future provide a testing ground for experimental observation

  18. Toward a microrealistic version of quantum mechanics. II

    International Nuclear Information System (INIS)

    Maxwell, N.

    1976-01-01

    Possible objections to the propensity microrealistic version of quantum mechanics proposed previously are answered. This version of quantum mechanics is compared with the statistical, particle, microrealistic viewpoint, and a crucial experiment is proposed designed to distinguish between these two microrealistic versions of quantum mechanics

  19. Introduction to quantum mechanics a time-dependent perspective

    CERN Document Server

    Tannor, David J

    2007-01-01

    "Introduction to Quantum Mechanics" covers quantum mechanics from a time-dependent perspective in a unified way from beginning to end. Intended for upper-level undergraduate and graduate courses this text will change the way people think about and teach quantum mechanics in chemistry and physics departments.

  20. Quantum selfish gene (biological evolution in terms of quantum mechanics)

    OpenAIRE

    Ozhigov, Yuri I.

    2013-01-01

    I propose to treat the biological evolution of genoms by means of quantum mechanical tools. We start with the concept of meta- gene, which specifies the "selfish gene" of R.Dawkins. Meta- gene encodes the abstract living unity, which can live relatively independently of the others, and can contain a few real creatures. Each population of living creatures we treat as the wave function on meta- genes, which module squared is the total number of creatures with the given meta-gene, and the phase ...