Monday March 24, 2008 6:40 am Edmonton, Alberta

This page last updated on: Sunday, April 20, 2008 9:15 AM

It is -2 C with a high forecast of +4 C. Sunrise 7:26 Sunset 19:54 Hours of daylight: 12:28

A. Morning Musings

This has been a very enjoyable weekend, but we drive back to Lethbridge today, with a quick stopover in Calgary.

Learning Category	Planned Activities for Today	Time
Literature	Begin morning with a Rumi reading
Literature	Continue reading "The Way the Crow Flies" by Ann-Marie MacDonald	1 hr
Science	Continue reading "Quantum: A Guide for the Perplexed" by Jim Al-Khalili	1 hr

B. Actual Learning Activities

6:45 am

Quantum: A Guide for the Perplexed (2003)

Jim Al-Khalili

Chapter 4 Spooky Connections

I read this chapter yesterday. There are a few key ideas, all of which are very much counter intuitive.

"In this chapter we investigate a few more of the strange concepts forced upon us by quantum mechanics. At the root of them all is the wavefunction. ... Just because we have mathematical formulae that allow us to calculate and predict properties of an atom does not mean that the wavefunction is a mathematical description of the atom itself or worse still that the wavefunction is the atom." [p. 80]

Superposition. The idea of superposition is not unique to quantum mechanics but is a general property of all waves. It is simply the process of adding different waves together. The result is called an interference pattern. The conceptual problem arises when one looks at the result of adding two such waves. This may mean that the resulting wavefunction describes a body that is in two different places at the same time, or of a body that has different velocities at different times. "... a quantum particle can be in a combination of two or more states at the same time." [p. 94]

As I see it the problem arises because when we consider a body (e.g. an electron) as a particle we can describe both its position and its velocity. However when we look at the wavefunction, or the wave emanating out from a position, we then have a consequence that occupies all of the space that the wave might have travelled in the time since the body was first observed. The two descriptions are not equivalent. One describes the motion at a single coordinate, the other describes the motion from an infinity of possible perspectives.

There is an excellent diagram on page 84 that illustrates the idea of superposition in terms of probability distributions.

insert diagram here

Particle Interferometers. I need to reread this section.
Nonlocality. "... two quantum particles (or two separate parts of the spread-out wavefunction of the same particle) can somehow rmain in touch with each other however far apart they are." [p. 94]
Entanglement. The idea is that two particles can "become correlated in the sense that their fates will be intertwined for ever, however far apart they get." [p. 94]
EPR Experiment. Einstein, Podolsky & Rosen (in 1935) came up with a thought experiment that highlights the idea that we cannot consider a particle to have a well-defined position unless we look at it.

Tags: physics, science, quantum

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Monday March 24, 2008 6:40 am Edmonton, Alberta

A. Morning Musings

B. Actual Learning Activities

6:45 am

Chapter 4 Spooky Connections