What is quantum mechanics trying to tell us?

I explore whether it is possible to make sense of the quantum mechanical description of physical reality by taking the proper subject of physics to be correlation and only correlation, and by separating the problem of understanding the nature of quantum mechanics from the hard problem of understanding the nature of objective probability in individual systems, and the even harder problem of understanding the nature of conscious awareness. The resulting perspective on quantum mechanics is supported by some elementary but insufficiently emphasized theorems. Whether or not it is adequate as a new Weltanschauung, this point of view toward quantum mechanics provides a different perspective from which to teach the subject or explain its peculiar character to people in other fields.Comment: 37 pages, no figures. This is the published version of the lecture notes that expand on my earlier ``Ithaca interpretation of quantum mechanics'', quant-ph/9609013. ``Wootters' theorem'' has become the SSC theorem, an earlier citation has been added, and a joke about Talmudic scholarship has been dropped at the request of a refere

From Cbits to Qbits: Teaching computer scientists quantum mechanics

A strategy is suggested for teaching mathematically literate students, with no background in physics, just enough quantum mechanics for them to understand and develop algorithms in quantum computation and quantum information theory. Although the article as a whole addresses teachers of physics, well versed in quantum mechanics, the central pedagogical development is addressed directly to computer scientists and mathematicians, with only occasional asides to their teacher. Physicists uninterested in quantum pedagogy may be amused (or irritated) by some of the views of standard quantum mechanics that arise naturally from this unorthodox perspective.Comment: 19 pages, no figures. Submitted to the American Journal of Physic

Nonlocal character of quantum theory?

In a recent article under the above title (but without the question mark) Henry Stapp presented arguments which lead him to conclude that under suitable conditions ``the truth of a statement that refers only to phenomena confined to an earlier time'' must ``depend on which measurement an experimenter freely chooses to perform at a later time.'' I point out that the reasoning leading to this conclusion relies on an essential ambiguity regarding the meaning of the expression ``statement that refers only to phenomena confined to an earlier time'' when such a statement contains counterfactual conditionals. As a result the argumentation does not justify the conclusion that there can be frames of reference in which future choices can affect present facts. But it does provide an instructive and interestingly different opportunity to illustrate a central point of Bohr's reply to Einstein, Podolsky, and Rosen.Comment: 11 pages, no figure

Copernican Crystallography

Redundancies are pointed out in the widely used extension of the crystallographic concept of Bravais class to quasiperiodic materials. Such pitfalls can be avoided by abandoning the obsolete paradigm that bases ordinary crystallography on microscopic periodicity. The broadening of crystallography to include quasiperiodic materials is accomplished by defining the point group in terms of indistinguishable (as opposed to identical) densities.Comment: 12 pages [The author apologizes for intruding on this archive, but suspects that this way of relaxing the definition of a group of transformations may be familiar to some of you in other contexts. He would welcome comments.

Deconstructing Dense Coding

The remarkable transmission of two bits of information via a single qubit entangled with another at the destination, is presented as an expansion of the unremarkable classical circuit that transmits the bits with two direct qubit-qubit couplings between source and destinationComment: 3 pages, 2 figure