http://www.thequantumexchange.org/ The latest material additions to the Quantum Exchange. en-US Copyright 2010, ComPADRE.org editor@thequantumexchange.org editor@thequantumexchange.org Fri, 03 Sep 2010 18:03:24 EST http://blogs.law.harvard.edu/tech/rss http://www.compadre.org/portal/services/images/LogoSmallQuantum.gif http://www.thequantumexchange.org/ 125 35 http://www.thequantumexchange.org/items/detail.cfm?ID=8915 We have investigated student difficulties in understanding and interpreting probability and its relevant technical terms as it relates to quantum measurement. These terms include expectation value, probability density, and uncertainty. From this research, it is evident that students have difficulties in understanding these terms and often fail to differentiate among similar but different concepts. In addition, students' difficulties with the concepts of probability often interfere with their understanding and application of the Uncertainty Principle. Education Foundations/Alternative Conceptions http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8915 Fri, 03 Sep 2010 18:03:24 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8915 http://www.thequantumexchange.org/items/detail.cfm?ID=10278 Quantum mechanics is difficult to learn because it is counter-intuitive, hard to visualize, mathematically challenging, and abstract. The Physics Education Technology (PhET) Project, known for its interactive computer simulations for teaching and learning physics, now includes 18 simulations on quantum mechanics designed to improve learning of this difficult subject. Our simulations include several key features to help students build mental models and intuitions about quantum mechanics: visual representations of abstract concepts and microscopic processes that cannot be directly observed, interactive environments that directly couple students' actions to animations, connections to everyday life, and efficient calculations so students can focus on the concepts rather than the math. Like all PhET simulations, these are developed using the results of education research and feedback from educators, and are tested in student interviews and classroom studies. This article provides an overview of the PhET quantum simulations and their development. We also describe research demonstrating their effectiveness and share some insights about student thinking that we have gained from our research on quantum simulations. Education Practices/Instructional Material Design/Simulation http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=10278 Fri, 03 Sep 2010 18:00:13 EST http://www.thequantumexchange.org/items/detail.cfm?ID=10278 http://www.thequantumexchange.org/items/detail.cfm?ID=10273 The Two Dimensional Schrodinger Equation model simulates the time evolution of a two-dimensional wave packet as it moves towards a slit with an obstacle in it, both with variable widths. By changing three parameters via sliders provided, slit width, obstacle width, and initial position of the wave packet, different behaviors can be explored. These phenomena include interference, diffraction produced by a slit, a corner, and an obstacle, and bouncing of the wave packet. In addition, the angle of propagation for the diffracted part of the wave packet can be measured. This simulation is described by a paper in the European Journal of Physics, "A versatile applet to explore the wave behaviour of particles, " J I Fernández Palop, 2009 Eur. J. Phys. 30 771, which outlines the simulation and how the usefulness of the simulation has been tested in the subject of quantum physics. The Two Dimensional Schrodinger Equation model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_schrodinger2d.jar file will run the program if Java is installed. Quantum Physics/Scattering and Continuum State Systems http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=10273 Fri, 03 Sep 2010 17:50:52 EST http://www.thequantumexchange.org/items/detail.cfm?ID=10273 http://www.thequantumexchange.org/items/detail.cfm?ID=3943 This set of quantum mechanics java applets, part of the Open Source Physics project, provides simulations that demonstrate the effect of measurement on the time-dependence of quantum states. Exercises are available that demonstrate the results of measurement of energy, position, and momentum on states in potential wells (square well, harmonic oscillator, asymmetric well, etc). Eigenstates, superpositions of eigenstates, and wave packets can all be studied. Tutorials are also available. The material stresses the measurement of a quantum-mechanical wave function. The simulations can be delivered either through the OSP Launcher interface or embedded in html pages. The source code is available, and users are invited to contribute to the collection's development by submitting improvements. The simulations are available through the "View attached documents" link below. Quantum Physics/Foundations and Measurement Theory http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=3943 Thu, 08 Jul 2010 05:31:04 EST http://www.thequantumexchange.org/items/detail.cfm?ID=3943 http://www.thequantumexchange.org/items/detail.cfm?ID=9513 The Stern Gerlach experiment has played a central role in the discovery of spin angular momentum and it has also played a pivotal role in elucidating foundational issues in quantum mechanics. Here, we discuss investigation of students' difficulties related to the Stern Gerlach experiment by giving written tests and interviewing advanced undergraduate and graduate students in quantum mechanics. We also discuss preliminary data that suggest that the Quantum Interactive Learning Tutorial (QuILT) related to the Stern Gerlach experiment is helpful in improving students' understanding of these concepts. Quantum Physics/Spin and Finite Dimensional Systems http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9513 Tue, 29 Jun 2010 23:20:26 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9513 http://www.thequantumexchange.org/items/detail.cfm?ID=9450 To guide research-based transformation of upper-division physics classes, it is useful to identify learning goals that are broadly supported by the faculty. Our efforts to transform our junior-level E&M course have revealed a broad faculty consensus on the content of the course, if not the pedagogical approach. In contrast, we find a range of opinions on both the content and the pedagogy in junior-level QM. We surveyed 27 faculty about their approaches to teaching QM, and reviewed 20 quantum textbooks. Although there is broad agreement on the list and order of topics (Schrödinger equation to matrix methods and spin), we find substantial disagreement in several pedagogical aspects, including (1) the importance of presenting QM on an axiomatic basis (i.e. the postulates); (2) the treatment of measurement in QM (in particular, the collapse of the wave function); and (3) the physical interpretation of the wave function (matter wave vs. information wave vs. something else). Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9450 Tue, 29 Jun 2010 23:14:11 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9450 http://www.thequantumexchange.org/items/detail.cfm?ID=4760 A good understanding of how students understand physics is of great importance for developing and delivering effective instructions. This research is an attempt to develop a coherent theoretical and mathematical framework to model the student learning of physics. The theoretical foundation is based on useful ideas from theories in cognitive science, education, and physics education. The emphasis of this research is made on the development of a mathematical representation to model the important mental elements and the dynamics of these elements, and on numerical algorithms that allow quantitative evaluations of conceptual learning in physics. Model analysis is used to determine common student models. The theory is applied to student understanding of quantum mechanics. Multiple-choice instruments to probe student models and a set of quantum tutorials are developed. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=4760 Tue, 29 Jun 2010 23:12:17 EST http://www.thequantumexchange.org/items/detail.cfm?ID=4760 http://www.thequantumexchange.org/items/detail.cfm?ID=7334 The Phase Matters package is a self-contained file for the teaching of phase and time evolution in quantum mechanics. The file contains ready-to-run OSP programs and a set of curricular materials. The material focuses on when and how, for arbitrary quantum-mechanical states, the phase of the wave function matters. The Phase Matters package is an Open Source Physics curricular package written for the teaching of quantum mechanics. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the osp_phase_matters.jar file will run the package if Java is installed. Other quantum mechanics packages are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Quantum Mechanics. Quantum Physics/Probability, Waves, and Interference http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=7334 Tue, 29 Jun 2010 23:06:08 EST http://www.thequantumexchange.org/items/detail.cfm?ID=7334 http://www.thequantumexchange.org/items/detail.cfm?ID=10072 The Magnetic Resonance of Spin One-Half Particles model simulates the magnetic resonance of a spin ½ particle. Users can vary the frequency of an oscillating magnetic field and see how the quantum spin responds. Users can also vary the magnitude of both the oscillating field and a static field to observe how this affects the resonance. The phenomenon of magnetic resonance is of practical importance, and the equations that describe magnetic resonance can be derived with relative ease. For this reason, the topic is appropriate for an undergraduate course in quantum mechanics, and it appears in some quantum mechanics textbooks. However, the equations cannot be solved analytically, so the treatment that is found in textbooks is relatively brief and involves confusing approximations. This simulation can hence provide a useful supplement for a course on quantum mechanics. Explanations of the physical system and both basic and advanced student activities are included with the model. The Magnetic Resonance of Spin One-Half Particles model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_fmu_MagneticResonance_SpinOneHalfParticles.jar file will run the program if Java is installed. Quantum Physics/Spin and Finite Dimensional Systems http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=10072 Wed, 09 Jun 2010 12:32:35 EST http://www.thequantumexchange.org/items/detail.cfm?ID=10072 http://www.thequantumexchange.org/items/detail.cfm?ID=9791 This student activity is designed to help upper division undergraduate students work with the mathematics of projection operators in quantum mechanics. Students will find normalized orthogonal vectors, take outer products of vectors with themselves, and explore the resulting projection operators. This material includes a student worksheet and instructor's guide. This material is part of the Paradigms in Physics project at Oregon State University. This work promotes the use of active student learning in upper division physics courses. Both learning materials and learning strategies are provided to help both students and instructors. Instructors using these materials are encouraged to add comments on their experiences to the wiki. Quantum Physics/Foundations and Measurement Theory http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9791 Thu, 18 Feb 2010 12:26:14 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9791 http://www.thequantumexchange.org/items/detail.cfm?ID=9790 This web page provides a list of learning activities for Quantum Mechanics classes. Each activity includes a description and learning goals, guides for instructors, handouts or worksheets, and reflections of instructors who have used the activity when available. Included are activities for Operators, Eigenstates, Probability Densities, Stern-Gerlach Simulations, Schrödinger's Equation, and Time Evolution. This material is part of the Paradigms in Physics project at Oregon State University. This work promotes the use of active student learning in upper division physics courses. Both learning materials and learning strategies are provided to help both students and instructors. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9790 Thu, 11 Feb 2010 21:16:03 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9790 http://www.thequantumexchange.org/items/detail.cfm?ID=9302 This web site provides research-based materials for junior-level quantum mechanics I courses on quantum mechanics. Topics covered include the Schroedinger equation, bound state problems, Hilbert space and operators, the hydrogen atom, and spin. The course archives include documented student difficulties, learning goals, ConcepTests (clicker questions), class activities, homework, tutorials, and a conceptual assessment tool. All may be downloaded, although the assessment tools require permission from the authors for access. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9302 Fri, 29 Jan 2010 19:11:47 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9302 http://www.thequantumexchange.org/items/detail.cfm?ID=6729 This web site is an entire web-based Quantum Mechanics I Course based at the University of Tennessee. It includes instructional materials, in-class tutorials, simulations, links to other quantum resources, homework assignments, and solutions. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=6729 Thu, 17 Sep 2009 12:38:52 EST http://www.thequantumexchange.org/items/detail.cfm?ID=6729 http://www.thequantumexchange.org/items/detail.cfm?ID=7336 The OSP QuILT package is a self-contained file for the teaching of time evolution of wave functions in quantum mechanics. The file contains ready-to-run OSP programs and a set of curricular materials. The material presents a computer-based tutorial on the “Time Evolution of the Wave Function.” This package is one of the recently developed computer-based tutorials that have resulted from the collaboration of the Quantum Interactive Learning Tutorials (QuILT) project and the Open Source Physics (OSP) project. The OSP QuILT package is an Open Source Physics curricular package written for the teaching of quantum mechanics. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the osp_quilt.jar file will run the package if Java is installed. Other quantum mechanics packages are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, QuILT, or Quantum Mechanics. Quantum Physics/Probability, Waves, and Interference http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=7336 Fri, 26 Jun 2009 22:08:34 EST http://www.thequantumexchange.org/items/detail.cfm?ID=7336 http://www.thequantumexchange.org/items/detail.cfm?ID=7613 We address four main areas in which graduate quantum mechanics education can be improved: course content, textbook, teaching methods, and assessment tools. We report on a three year longitudinal study at the Colorado School of Mines using innovations in all these areas. In particular, we have modified the content of the course to reflect progress in the field of quantum mechanics over the last 50 years, used textbooks that include such content, incorporated a variety of teaching techniques based on physics education research, and used a variety of assessment tools to study the effectiveness of these reforms. We present a new assessment tool, the Graduate Quantum Mechanics Conceptual Survey, and further testing of a previously developed assessment tool, the Quantum Mechanics Conceptual Survey. We find that graduate students respond well to research-based techniques that have been tested mainly in introductory courses, and that they learn much of the new content introduced in each version of the course. We also find that students' ability to answer conceptual questions about graduate quantum mechanics is highly correlated with their ability to solve calculational problems on the same topics. In contrast, we find that students' understanding of basic undergraduate quantum mechanics concepts at the modern physics level is not improved by instruction at the graduate level. Education Practices/Curriculum Development/Course http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=7613 Wed, 24 Jun 2009 07:21:19 EST http://www.thequantumexchange.org/items/detail.cfm?ID=7613 http://www.thequantumexchange.org/items/detail.cfm?ID=4964 This website provides a broad online introduction to lasers. The topics covered include basic optics and radiation, quantum energy levels, laser systems, gain, types of lasers, and laser applications. The online text also contains java applets to illustrate the physics and links related to lasers such as a list of books on lasers and laboratory experiments. Optics/Modern Optics/Lasers http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=4964 Wed, 24 Jun 2009 07:19:40 EST http://www.thequantumexchange.org/items/detail.cfm?ID=4964 http://www.thequantumexchange.org/items/detail.cfm?ID=3233 While the classical, wavelike behavior of light (interference and diffraction) has been easily observed in undergraduate laboratories for many years, explicit observation of the quantum nature of light (i.e., photons) is much more difficult. For example, while well-known phenomena such as the photoelectric effect and Compton scattering strongly suggest the existence of photons, they are not definitive proof of their existence. Here we present an experiment, suitable for an undergraduate laboratory, that unequivocally demonstrates the quantum nature of light. Spontaneously downconverted light is incident on a beamsplitter and the outputs are monitored with single-photon counting detectors. We observe a near absence of coincidence counts between the two detectors—a result inconsistent with a classical wave model of light, but consistent with a quantum description in which individual photons are incident on the beamsplitter. More explicitly, we measured the degree of second-order coherence between the outputs to be g(2)(0) = 0.0177±0.0026, which violates the classical inequality g(2)(0)>=1 by 377 standard deviations. Quantum Physics/Quantum Experiments http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=3233 Wed, 20 May 2009 00:20:21 EST http://www.thequantumexchange.org/items/detail.cfm?ID=3233 http://www.thequantumexchange.org/items/detail.cfm?ID=7344 This web page gives a brief introduction to the double slit experiment in quantum mechanics illustrated by a java applet. The applet is a simulation of a 2D interference experiment with user changeable slit size, detector position, and whether there is one or two slits. The description of the experiment gives a brief introduction to the concepts of the wavefunction providing probabilities and measurements causing a collapse of the wavefunction. Quantum Physics/Probability, Waves, and Interference http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=7344 Tue, 19 May 2009 23:48:49 EST http://www.thequantumexchange.org/items/detail.cfm?ID=7344 http://www.thequantumexchange.org/items/detail.cfm?ID=4336 This research paper, presented at the 2002 Physics Education Research Conference, discusses the authors' research on student use of resources in learning quantum mechanics, which shows that a student often needs to make judgments among competing ideas. The researchers state that they see the potential to develop a new category of resources, meta-resources, to model the views and beliefs as well as meta-cognitive processes that students use in making judgments. Examples from student interviews are discussed as initial evidence for a larger scale investigation toward this area. Education Foundations/Cognition http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=4336 Tue, 19 May 2009 17:17:05 EST http://www.thequantumexchange.org/items/detail.cfm?ID=4336 http://www.thequantumexchange.org/items/detail.cfm?ID=8540 This web site provides interactive representations of quantum optics experiments. The illustrations show the setup, operation, and results of real experiments that demonstrate fundamental phenomena of quantum physics such as quantum particles, randomness, and entanglement as well as prospective applications such as quantum number generation and quantum cryptography. Extensive supplemental materials, with text, pictures, and video, explain the physics being studied in the experiments. An extensive bibliography is also included. Quantum Physics/Foundations and Measurement Theory http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8540 Tue, 17 Feb 2009 13:05:35 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8540