The Strange World of Quantum Mechanics

Oberlin College Physics 52

Syllabus for Spring 2018

Why would anyone want to take a course called "The Strange World of Quantum Mechanics"?

Just over 100 years ago, physicists exploring the newly discovered atom found that the atomic world of electrons and protons is not just smaller than our familiar world of trees, balls, and automobiles, it is also fundamentally different in character. Objects in the atomic world obey different rules from those obeyed by a tossed ball or an orbiting planet. These atomic rules are so different from the familiar rules of everyday physics, so counterintuitive and unexpected, that it took more than 25 years of intense research to uncover them.

But it is really only in the last 10 or 20 years that we have come to appreciate that the rules of the atomic world (now called "quantum mechanics") are not just different from the everyday rules (now called "classical mechanics"). The atomic rules are also far richer. The atomic rules provide for phenomena like particle interference and entanglement that are simply absent from the everyday world. Every phenomenon of classical mechanics is also present in quantum mechanics, but the quantum world provides for many additional phenomena. (These are the phenomena currently being exploited in the emerging field of quantum computing.)

Just as a flat map is a good approximation to a globe -- so long as one takes only short journeys; so classical mechanics is a good approximation to quantum mechanics -- so long as one investigates only objects larger than molecules.

Here's another analogy: Some films are in black-and-white and some are in color. It does not malign any black-and-white film to say that a color film has more possibilities, more richness. In fact, black-and-white films are simply one category of color films, because black and white are both colors. Anyone moving from the world of only black-and-white to the world of color is opening up the door to a new world -- a world ripe with new possibilities and new expression -- without closing the door to the old world.

This same flood of richness and freshness comes from entering the quantum world. It is a difficult world to enter, because we humans have no experience, no intuition, no expectations about this world. Even our language, invented by people living in the everyday world, has no words for the new quantal phenomena -- just as a language among a race of the color-blind would have no word for "red".

This course is not easy: it is like a color-blind student learning about color from a color-blind teacher. The course is just one long argument, building up the structure of a world that we can explore not through touch or through sight or through scent, but only through logic. Those willing to follow and to challenge the logic, to open their minds to a new world, will find themselves richly rewarded.

Topics: This course introduces the three central concepts of quantum mechanics, namely: (1) The outcome of an experiment cannot, in general, be predicted exactly; only the probability of the various outcomes can be found. (2) These probabilities arise through the interference of probability amplitudes. (3) Probability amplitudes can be associated with two experiments done far apart from each other ("entanglement"). The ideas are developed through the example of an intrinsically simple system ("spin 1/2"), which is treated with complete rigor and honesty.

Leering goals: Through your work in this course, you will

Teacher: Dan Styer, Wright 215, 775-8183,
home telephone 440-281-1348 (2:30 pm to 9:00 pm only).
My schedule grid (PDF).

Course web site (this document):

Add-drop warning: If you wish to add or drop this course, you must do so via PRESTO by 11:30 pm on Wednesday, 4 April 2018.

Prerequisites: This course does not assume any background in science. High school algebra and geometry will be used as needed without apology.

Text: D.F. Styer, The Strange World of Quantum Mechanics.

Tutoring: Tutors are available for this course at no charge through Oberlin College's office of Student Academic Services. See Donna Young at Peters 118, weekdays 8:30 am - noon or 1:30 pm - 4:00 pm.

Grading: This is a second-half-of-the-semester half course, graded on a Pass/No Pass basis. To receive credit, you must react to classes regularly and satisfactorily complete six assignments. A project may be substituted for 40% of the assignment questions. There are no exams. (I find it impossible to think up exam questions for quantum mechanics at this level: the questions I come up with are either too hard or else not probing.)

How do you react to classes? At the end of every class, hand in a slip of paper containing your name and a brief (one- or two-sentence) reaction to the state of your knowledge concerning quantum mechanics. I will use these reactions to plan the next class and the future path of this course. Your most useful reaction would be a specific question: for example, "What does it mean to say that an electron does not have a position?" Other possible reactions would be indications of general interest ("I'd like to learn more about entanglement.") or general questions ("Why should I care about this stuff, anyway?"). Please avoid questions of marginal relevance to this course ("How can I get that cute redhead in the second row to notice me?").

Assignments are due at the end of the day (11:59 pm) on each Thursday except for the last Thursday of the course (10 May). They will be administered and graded through the Oberlin College Blackboard system. You may rework an assignment as many times as you wish before the deadline. In working an assignment, you may consult any written or on-line material, or you may consult your friends, but you must complete the assignment yourself . . . you may not, for example, copy answers from someone who has already done the assignment. I cannot accept late solutions. To pass the course, you must earn at least 70% on the assignments. (I appreciate that for some of the assignments you might be sick or for other reasons not at the peak of your abilities. That's why the 70% cutoff is set so low.)

The problem assignments are an opportunity for you hone your growing quantum-mechanical skills and knowledge by applying them to specific situations. It's easy to fool yourself into thinking that you understand quantum mechanics because you can follow the readings and grasp the outlines of the theory, whereas in fact understanding comes through knowing not just the theory, but also how to apply it. (Just as everyone wants a free, stable, unified, and democratic Korea, but no one seems to know how to get from where we are to this laudable goal.)

Project: If your assignment grade is too low, or if you wish to skip some of the assignments, then you may make 40% of your grade through a project. The project is usually an essay concerning quantum mechanics, the history of quantum mechanics, or the influence of quantum mechanics on philosophy, literature, culture, etc. Possible essay topics are listed in appendix D of the book, but I'm sure you will be able to come up with other good ideas yourself. Restrict the scope of your investigations...I would far prefer a short, well-thought-out investigation to a long discourse that merely parrots the opinions found in some library book. Your project may be a creative work such as a poem, short story, or piece of music, but it must involve quantum mechanics in some non-trivial way! I anticipate that your essay will be relatively short (three to six pages), but it should show evidence of considerable analytic thought. The project is due at the last class meeting on 10 May 2018.

Honor code: In working an assignment or project, you may consult any written or on-line material, or you may consult your friends (or your enemies!), but you must complete the assignment yourself . . . you may not, for example, copy answers from someone who has already done the assignment. In the project, you must cite and/or acknowledge written, on-line, and friend (or enemy) resources used.

This is the standard rule for intellectual discourse: When I write a research paper on quantum mechanics, I consult other materials, and before publication I always give the paper to a friend who suggests improvements. But I always cite the materials, I always acknowledge the friend, and I never copy an already published research paper.

Course schedule:
Relevant readings from textbook The Strange World of Quantum Mechanics are listed in square brackets.

27 March Introduction
29 March Feynman on quantum mechanics (movie) [chap. 1]
[Movie available at]
3 April Classical magnetic needles (demonstrations) [chap. 2]
5 April Conundrum of projections; Repeated measurements [chaps. 3 and 4]
10 April Probability [chap. 5]
12 April Einstein-Podolsky-Rosen paradox [chap. 6]
17 April Optical interference (demonstrations) [chap. 8]
19 April Quantal interference [chap. 9]
24 April Amplitudes [chaps. 10 and 11]
26 April Quantum cryptography [appendix B and chap. 13]
1 May Quantum mechanics of a bouncing ball [chap. 14]
3 May History of quantum mechanics
8 May Relativistic quantum mechanics (descriptive lecture)
10 May Summary

Bibliography for "The Strange World of Quantum Mechanics"

The following books are on reserve in the science library. (Most are located on shelves along the south wall, not far to your right when you enter, near some comfy chairs to encourage browsing.)

D.F. Styer, The Strange World of Quantum Mechanics [Science QC174.12.S879 2000]
The course textbook is on reserve behind the science library desk.

R.P. Feynman, QED: The Strange Theory of Light and Matter [Science QC793.5.P422F48 1985]
Quantum mechanics in more different situations.

R.P. Feynman, Character of Physical Law [Mudd 530.04 F438C]
Includes (chapter 6) a transcript of the lecture shown in the second class.

T.F. Jordan, Quantum Mechanics in Simple Matrix Form [Science QC174.12.J67 1986]
A mathematical approach to quantum mechanics.

M. Chester, Primer of Quantum Mechanics [Science QC174.12.C46 2003]
Another mathematical approach to quantum mechanics.

George Greenstein and Arthur G. Zajonc, The Quantum Challenge: Modern Research on the Foundations of Quantum Mechanics (second edition) [Science QC174.12.G73 1997]
Experiments concerning the foundations of quantum mechanics.

J.M. Jauch, Are Quanta Real? [Mudd 530.12 J321A]
A popularization of quantum mechanics in the form of a Galilean dialog.

J.C. Polkinghorne, The Quantum World [Science QC174.12.P64 1989]
Written by a physicist turned priest.

Graham Farmelo, The Strangest Man: The Hidden Life of Paul Dirac [Science QC16.D57 F37 2009b]

Helge Kragh, Dirac: A Scientific Biography [Science QC16.D57 K73 1990]

Susan Strehle, Fiction in the Quantum Universe [Mudd PS374.P45S77 1992]

Tom Stoppard, Hapgood [Science PR6069.T6H3 1988].
A sophisticated spy play involving quantum mechanics.

Want to know more?

Do you want to continue exploring our universe after this course is over?