Homework 3

Styer, Chapter 5:

1. 5.7
2. 5.8

1. 6.2

1. 8.2

1. Suppose the left particle is measured first and the setting on the apparatus is A. Suppose this left measurement is +. Show that the probability that the right particle is measured to be + is 1/2.
2. Suppose the left particle is measured first and the setting on the apparatus is B. Suppose this left measurement is +. Show that the probability that the right particle is measured to be + is 1/2.

Short essay. Answer only one of these questions. Write as if you're writing to another student in the class. That is, assume your reader has read Styer's book and understood most of it, but that he or she is not an expert in quantum mechanics. I'd guess that a good response to these questions will be between 1 and 3 pages.

• In your own words, describe the EPR paradox. What is it that bothered Einstein so much? There's no need to go into the details of the Aspect experiment -- focus on what was paradoxical to Einstein. In your answer, you might want to quote comments from Einstein's paper, or Mermin or Styer. This is fine and is probably a good thing to do (be sure to cite your source). However, be sure to also restate any quotes you use.

• The Ghost in the Atom, edited by P.C.W.Davies and J.R. Brown, contains interviews of Alain Aspect and John Bell. This book is on reserve in the library. Read one of these interviews and comment and/or respond. Assume that your reader has not read the interview, so part of your task is to summarize what you think was important or interesting from the interview.

• In class and in Styer's book, many of the details and experimental challenges of Aspect's work were left out. Read more about the experiment and write an explanation understandable to others in the class. Possible things to focus on: How are the two photons produced? How to the detectors actually work? How does the coincidence counter come into play? To answer these, you'll need to look at Aspect's paper, and probably some other sources. If you're interested in this, see me for some pointers to various references.

• There are lots of essays on the web about EPR and such. Find one and write a thoughtful, constructive review of it. Do you find any errors? Compare it to Mermin's article and Styer's chapter 6. Which would you recommend to a beginning quantum mechanics student, and why? If you choose this option, you should clear with me what you're writing a review of before you write it.

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