Visual Quantum Mechanics

The making of VQM

Visual Quantum Mechanics (VQM) is a project that has occupied my spare time for several years. This page tells about the history, the philosophy, and the making of VQM.

In 1996 I learned in more detail about Mathematica's graphics capabilities and, like many others, I decided to make use of these capabilities in my lectures. Originally, I planned to do something like "Quantum Mechanics with Mathematica", but I found that students interested in quantum mechanics do not always have a good background in computer algebra systems. I made the experience that it is not reasonable to teach quantum mechanics and Mathematica at the same time. If a student only works 'online' to learn quantum mechanics, he would not aquire the basic mathematical skills which are necessary to understand quantum mechanics on a professional level. On the other hand, the visualizations and movies were found to be very useful for explaining and motivating quantum mechanics. So I used the approach to teach quantum mechanics in a more or less conventional manner with ready-made movies as a teaching aid. The student would not learn how to make these films, but he/she would acquire a deeper and more intuitive understanding of quantum mechanics and a better familiarity with quantum mechanical phenomena.

I think that I myself learned most from the making of these movies. I was surprised by many unexpected features of quantum wave functions. I could learn very interesting facts even about the simplest quantum systems, like the particle in a box or the harmonic oscillator. (Yes, indeed, some of the movies showed effects that were new to me despite the fact that I have been doing research in quantum mechanics for many years.)

Over the time I created a lot of movies and finally I decided to make them available to a wider audience. Originally, I intended to write just a short comment for each movie which should explain the theoretical background, draw some conclusions, and provide some documentation (e.g., values of parameters, initial function, method of solution). At this point I realized that each movie indeed contains an awful lot of information. A full explanation of everything that can be seen in the movies soon becomes a complete quantum mechanics course on a rather advanced level. When I came across "The Picture Book of Quantum Mechanics" by S.Brandt and H.D.Dahmen I had the idea for a "Movie Book of Quantum Mechanics" - a quantum mechanics text that encourages the use of the computer, but does not require any special computer skills to benefit from the presentation.

Several decisions about the design of the software part had to be made at a very early stage of the project. The first decision was to use QuickTime as the leading multiplatform standard for displaying movies. A more difficult decision was about how to present the movies. One could just put a collection of QuickTime files on a CD-ROM and cite the name of the movie file at the appropriate place in the textbook. But I wanted to include all documentation relevant to the movies on the CD-ROM. So I wanted a form of presentation, where it is easy to display some text next to the movie, and show the relevant formulas in the case that the process can be described analytically. In order to make the documentation complete, it should also be possible to display the Mathematica source of the movie.

During the beginning of the project in 1996 I considered the following multi-platform options of making a movie presentation:

  • HTML - view with a Web browser (needs the QuickTime-plugin)
  • PDF - view with Adobe Acrobat.
  • Macromedia Director - stand alone application

All these variants had advantages and disadvantages. I finally decided for a presentation using Macromedia Director, which provides the best means for true interactivity. Moreover, it opens additional possibilities to create animations and offers unlimited freedom for the graphical design. Among the disadvantages of Director are the following: A lot of programming in Lingo has to be done even for simple things like buttons and hyperlinks, and the behavior of QuickTime movies is somewhat difficult to predict from the available documentation (although the QuickTime implementation of Director has improved greatly with version 7.2.1).

Among the numerous difficulties I had to face on the practical side, let me just mention one. When I was preparing one of the final versions of the CD-ROM, Apple switched from QuickTime 2.1 to QuickTime version 3.0. Version 3 comes with a completely new application interface for Windows programs, and the available versions of Macromedia Director (6.0 and earlier) did not support the new version of QuickTime on the Windows platform. This would not have been a problem, if I had been allowed to distribute the old QuickTime version together with the Macromedia presentation (which worked fine). But for a few terrible months it appeared as if Apple would not licence the old version of QuickTime any longer. Finally, Apple decided to license also the older version, but---as soon as Director 6.5 became available---I had already made the decision to spend some weeks upgrading everything to QuickTime 3. This actually caused many further problems when I had to upgrade the project again to the newest Director version 7. This version offered some advantages, but it also followed an approach of implementing QuickTime which was substantially different from the approach of older versions. As a result, I had to rewrite and redisign the whole presentation framework once more. Meanwhile, fortunately, everything works with the newest version of QuickTime and Director and, according to my impression the software is now advanced enough so that future upgrades can be done in a smoother way.