Sunday, February 01, 2009

Update as we start February

My contract has now finished, and to celebrate I've started the first book of the OU's Quantum Mechanics course, SM358. With no messing around, we're straight into wave-particle duality, 'collapse of the wave function' implying 'spooky action-at-a-distance', and probability amplitudes.

I was a tiny bit irritated by a throwaway reference in the text to the Mach-Zehnder Interferometer, where it was baldly stated that the quantum-theoretic interference effects were consistent with a classical (Maxwellian) interference story.

The OU diagram: Mach-Zehnder Interferometer

However, the over-simplified diagram in the book (above) gave no clue as to the mechanism for classical interference. In reality, it depends upon the details of phase-changes on the two paths, associated with reflection and transmission through the half-silvered and regular mirrors: not entirely trivial, as explained here.

A more useful diagram

Note that in this diagram we can see the construction of the mirrors, and whether light goes through the mirror-glass before getting reflected at the back-surface or not. Unfortunately, these details exactly determine the overall phase change: if they are ignored the resultant effect is incomprehensible.

Also started 2666, which I have to review as an Amazon Vine book. So far it's interesting, the characters are well-defined, and it's stylistically baroque. But still a long way to go.

We await the tidal wave of snow promised for tomorrow ...