http://www.thequantumexchange.org/ The latest material additions to the Quantum Exchange. en-US Copyright 2012, ComPADRE.org editor@thequantumexchange.org editor@thequantumexchange.org Wed, 18 Jan 2012 10:13:12 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=11667 This animation shows a system of N non-interacting Bose or Fermi particles in an infinitely deep square well. The total involves the distribution of the individual particles across energy levels. Users can choose the type and number of particles in the well and the total energy of the system. This animation includes a step-by-step exploration that explains key points in detail. This animation is part of a collection of animations for the teaching of concepts in quantum mechanics. Quantum Physics/Multi-particle Systems http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=11667 Wed, 18 Jan 2012 10:13:12 EST http://www.thequantumexchange.org/items/detail.cfm?ID=11667 http://www.thequantumexchange.org/items/detail.cfm?ID=8917 We developed a survey to probe student understanding of quantum mechanics concepts at the beginning of graduate instruction. The survey was administered to 202 graduate students in physics enrolled in first-year quantum mechanics courses from seven different universities at the beginning of the first semester. We also conducted one-on-one interviews with fifteen graduate students or advanced undergraduate students who had just finished a course in which all the content on the survey was covered. We find that students share universal difficulties about fundamental quantum mechanics concepts. The difficulties are often due to over-generalization of concepts learned in one context to other contexts where they are not directly applicable and difficulty in making sense of the abstract quantitative formalism of quantum mechanics. Instructional strategies that focus on improving student understanding of these concepts should take into account these difficulties. The results from this study can sensitize instructors of first-year graduate quantum physics to the conceptual difficulties students are likely to face. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8917 Fri, 18 Nov 2011 09:38:59 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8917 http://www.thequantumexchange.org/items/detail.cfm?ID=8921 We have studied whether repeated exposure to complicated physics concepts, such as quantum tunneling, fosters increased understanding. For three students, we have multiple interview, survey, and examination data over three years. We present data from a single student whose understanding of energy conservation in tunneling improved with repeated instruction, but whose ability to correctly sketch wave function solutions and discuss their meaning showed little progress. Education Foundations/Alternative Conceptions http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8921 Fri, 18 Nov 2011 09:37:08 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8921 http://www.thequantumexchange.org/items/detail.cfm?ID=7548 Some education researchers have claimed that we should not teach the Bohr model of the atom because it inhibits students’ ability to learn the true quantum nature of electrons in atoms. Although the evidence for this claim is weak, many have accepted it. This claim has implications for how to present atoms in classes ranging from elementary school to graduate school. We present results from a study designed to test this claim by developing a curriculum on models of the atom, including the Bohr and Schrödinger models. We examine student descriptions of atoms on final exams in transformed modern physics classes using various versions of this curriculum. We find that if the curriculum does not include sufficient connections between different models, many students still have a Bohr-like view of atoms rather than a more accurate Schrödinger model. However, with an improved curriculum designed to develop model-building skills and with better integration between different models, it is possible to get most students to describe atoms using the Schrödinger model. In comparing our results with previous research, we find that comparing and contrasting different models is a key feature of a curriculum that helps students move beyond the Bohr model and adopt Schrödinger’s view of the atom. We find that understanding the reasons for the development of models is much more difficult for students than understanding the features of the models. We also present interactive computer simulations designed to help students build models of the atom more effectively. Modern Physics/Atomic Physics/Atomic Models http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=7548 Fri, 18 Nov 2011 06:53:40 EST http://www.thequantumexchange.org/items/detail.cfm?ID=7548 http://www.thequantumexchange.org/items/detail.cfm?ID=11278 This web page is the home for the Quantum Mechanics Conceptual Survey (QMCS). The goal of this assessment is to provide an accurate measure of students' understanding of fundamental concepts in quantum mechanics. The QMCS is inspired by the many carefully researched and validated tests of conceptual understanding in physics. The authors developed the questions to be independent of notation unique to a specific course and avoiding jargon as much as possible. The questions in the QMCS are based on faculty interviews, textbooks and syllabi, existing assessments, research on student misconceptions in quantum mechanics, and student observations. Education Foundations/Assessment/Conceptual Assessment http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=11278 Fri, 18 Nov 2011 06:52:02 EST http://www.thequantumexchange.org/items/detail.cfm?ID=11278 http://www.thequantumexchange.org/items/detail.cfm?ID=10535 The Gaussian Wave Packet: Step Scattering model simulates the time evolution of a free Gaussian wave packet in position space when it is incident on a potential energy step.  The position-space wave functions are depicted using three colors on the graph: black which depicts the absolute square of the wave function, blue which depicts the real part of the wave function, and red which depicts the imaginary part of the wave function. The user may change the height of the potential step or the wave packet energy by dragging circles on the energy graph. The initial width of the packet may also be changed. Also shown are the theoretical and calculated transmission and reflection coefficients. The Gaussian Wave Packet: Step Scattering 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_gaussian_step.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=10535 Mon, 01 Aug 2011 10:33:32 EST http://www.thequantumexchange.org/items/detail.cfm?ID=10535 http://www.thequantumexchange.org/items/detail.cfm?ID=11356 This web site contains active-learning tutorials and writing assignments for upper-level undergraduate quantum mechanics. The tutorials focus on the mathematical formalism of quantum mechanics. The writing assignments focus on the interpretation of quantum mechanics, and particularly the role of experiments. The topics cover range from introduction to the Schrodinger equation through perturbation theory. In the course using these materials, students work in small groups to complete worksheet-based tutorials during class time, and do fairly typical homework problems and writing assignments, on their own. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=11356 Mon, 01 Aug 2011 10:27:19 EST http://www.thequantumexchange.org/items/detail.cfm?ID=11356 http://www.thequantumexchange.org/items/detail.cfm?ID=11188 This is a collection of animations for the teaching of concepts in quantum mechanics. Each animation includes a step-by-step exploration that explains key points in detail, and most animations include password-protected instructor resources consisting of worksheets with solutions. These animations build on existing education research and the experience of the authors. Each animation specifically targets student misconceptions and areas of difficulty in quantum mechanics. Animations have been used and evaluated in several quantum mechanics courses. The topics covered include bound states in one and two dimensions, scattering states, perturbations, Fermi and Bose statistics, and quantum logic. The development of further animations and extension of site functionality are ongoing. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=11188 Wed, 18 May 2011 23:31:52 EST http://www.thequantumexchange.org/items/detail.cfm?ID=11188 http://www.thequantumexchange.org/items/detail.cfm?ID=8575 This Mathematica notebook contains solutions to several numerical problems and exercises in quantum mechanics. Topics include the shooting method, wavepacket dynamics, probability functions, and the Laplace equation. All of the problems are in one dimension, to help students focus on the physics of quantum systems. Quantum Physics/Approximation Techniques http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8575 Sun, 15 May 2011 00:02:10 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8575 http://www.thequantumexchange.org/items/detail.cfm?ID=9523 We investigate the difficulties that undergraduate students in quantum mechanics courses have in transferring learning from previous courses or within the same course from one context to another by administering written tests and conducting individual interviews. Quantum mechanics is abstract and its paradigm is very different from the classical one. A good grasp of the principles of quantum mechanics requires creating and organizing a knowledge structure consistent with the quantum postulates. Previously learned concepts such as the principle of superposition and probability can be useful in quantum mechanics if students are given opportunity to build associations between new and prior knowledge. We also discuss the need for better alignment between quantum mechanics and modern physics courses taken previously because semi-classical models can impede internalization of the quantum paradigm in more advanced courses. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9523 Sat, 14 May 2011 23:31:07 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9523 http://www.thequantumexchange.org/items/detail.cfm?ID=9475 In order to help students overcome documented difficulties learning quantum mechanics (QM) concepts, we have transformed our upper-division QM I course using principles of learning theory and active engagement. Key components of this process include establishing learning goals and developing a valid, reliable conceptual assessment tool to measure the extent to which students achieve these learning goals. The course learning goals were developed with broad faculty input, and serve as the basis for the design of the course assessment tool. The development of the assessment tool has included significant faculty input and feedback, twenty-one student interviews, a review of PER literature, and administration of the survey to two semesters of QM I students as well as to a cohort of graduate students. Here, we discuss this ongoing development process and present initial findings from our QM class for the past two semesters. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9475 Sat, 14 May 2011 23:28:59 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9475 http://www.thequantumexchange.org/items/detail.cfm?ID=8999 Quantum mechanics is both a topic of great importance to modern science, engineering, and technology, and a topic with many inherent barriers to learning and understanding. Computational resources are vital tools for developing deep conceptual understanding of quantum systems for students new to the subject. This article outlines two projects that are taking an open source/open access approach to create and share teaching and learning resources for quantum physics. The Open Source Physics project provides program libraries, programming tools, example simulations, and pedagogical resources for instructors wishing to give a rich experience to their students. These simulations and student activities are, in turn, being integrated into a world-wide collection of teaching and learning resources available through the Quantum Exchange, a part of the ComPADRE Portal to the National Science Digital Library. Both of these projects use technologies that encourage community development and collaboration. Using these tools, faculty can create learning experiences, share and discuss their content with others, and combine resources in new ways. Examples of the available content and tools are given, along with an introduction to accessing and using these resources. Quantum Physics/General http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=8999 Sat, 12 Mar 2011 22:50:33 EST http://www.thequantumexchange.org/items/detail.cfm?ID=8999 http://www.thequantumexchange.org/items/detail.cfm?ID=10591 This web site seeks to give a non-technical, intuitive introduction to the quantum theory of the light field. Recent measurement data is employed to illuminate abstract quantum mechanical concepts such as the uncertainty relation, the wave packet, quantum noise, Wigner function, squeezed states, density matrices, etc., using the concrete example of the freely propagating light field. The web site includes a Java animation illustrating common quantum states of the light field, showing their experimentally measured quantum noise distribution and the corresponding motion of their wave packet. Quantum Physics/Quantum Experiments http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=10591 Sat, 12 Mar 2011 22:41:16 EST http://www.thequantumexchange.org/items/detail.cfm?ID=10591 http://www.thequantumexchange.org/items/detail.cfm?ID=9773 The QM Measurement Launcher package is a self-contained file for the teaching of the measurement (E, x, and p) of energy eigenstates and their superpositions in quantum mechanics. The file contains ready-to-run OSP programs and a curricular materials. One can choose from several pre-set states to perform measurements on: energy eigenstates, two-state superpositions, and wave packets. The QM Measurement package includes two supplemental documents (see below) that contain curricular worksheets in support of the package. The QM Measurement 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_superposition.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/Foundations and Measurement Theory http://www.thequantumexchange.org/bulletinboard/Thread.cfm?ID=9773 Fri, 14 Jan 2011 14:06:19 EST http://www.thequantumexchange.org/items/detail.cfm?ID=9773 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