Friday, April 15, 2016

Bee on essentials of quantum mechanics

Bee and Lumo are mostly in agreement on what quantum mechanics is about. Rather than nitpick, I emphasize where they are right, and most of the popular explanations are wrong.
Quantization doesn’t necessarily imply discreteness
Common explanations say that everything must be discrete, that the world is made of particles, and that even spacetime must be grainy.

Quantum mechanics says that eigenvalues are observed, and the spectrum can be continuous or discrete. Photons are not really discrete; they are just observed that way when emitted or absorbed by atoms because of the energy spectrum of electron orbitals.

Read my motto. Nature is continuous.

Many of the quantum gravity folks are eager to argue that everything is discrete. The new best-selling Rovelli book concludes that "space is granular, time does not exist, and things are nowhere". No, this is a misrepresentation of quantum mechanics.
There is no spooky action at a distance
People claim that spooky action was proved by Einstein or Bell or quantum computers. Nope.

This recent paper on Bell interpretations says that the conventional view is that Bell experiments prove spooky action at a distance. So does this recent blog post. This conventional view is wrong.
Schrödinger’s cat is dead. Or alive. But not both.
A more interesting question is whether quantum computers can do a super-Turing computation based on qubits being on and off at the same time. I argue that it is impossible. Those who say it must be possible based on quantum mechanics are suffering from an extension of the Schroeding cat fallacy.

1 comment:

  1. Roger, you might want to clarify as to what you mean by continuous. I think you are trying to take sides in a false dichotomy. Continuous implies infinitely discrete, at least in foundational mathematics that attempts to establish analysis. It's the degenerate limiting case of discreteness. I say all the sensible parts boil down to finite algebra.