Saturday, August 6, 2016

The Schrödinger Sessions: Day 3

(Picture from here.)

The Schrödinger Sessions are a collection of lectures and demonstrations of quantum physics for science fiction writers. (See here.) They are a joint production between the Joint Quantum Institute at the University of Maryland and the National Science Foundation. The three organizers are Chad Orzel, Emily Edwards and Steve Rolston. Three of the most terrific people I've ever met.

JQI is what they call low energy quantum mechanics. This involves quantum computation, low temperatures, superconductivity-- all of those sorts of things we can do in a relatively small lab. High energy quantum mechanics and physics, those things done at the Large Hadron Collider and supernovas, aren't done at JQI. That didn't prevent us from asking about it.

I found out about it when I checked out the launchpad astronomy workshop. I went down. I did the seminar. This is my little diary. It's a week late in that I wanted a chance to clean it up before I published it.

Day 3
We had only a ½ day before the end. This involved three things: a quick discussion of quantum applications, a free for all with questions and a discussion with Nobel Prize Winner Bill Phillips on quantum interpretations.

The quantum applications went quickly. MRIs, GPS and, essentially, all of chemistry. We also had a quick discussion of the Pauli Exclusion Principle, which I mentioned before. It's worth repeating.

In a nut shell, this says that two particles cannot occupy the same state. For example, if two electrons are in the first orbital of a hydrogen they must be of differing spins. In the next orbital, more electrons are allowed but the addition of the orbital number, plus spin, insures there are no more than can be accounted for by the differing states. And so on.

The PEP is what keeps electrons in discrete orbitals of the atom, giving the differing atoms their different chemical properties. Turns out there is something analogous to orbitals in the nucleus, too, which makes neutrons necessary in larger atoms.

During the free-for-all we got a little more understanding on how to look at measurement. For example, if you put an atom into a superposition state, close the door and leave the room. Go home to your spouse, have a pizza and watch TV. The next morning you come in and open up the trap and lo! The atom is no longer in superposition. Now under these conditions, at NO time was there an intentional measurement of the superposition. The loss of superposition was because of thermal noise or a stray atom or something else—which acted the same as if  human being was doing the measurement.

Consequently, the whole term “measurement” is a bad English. In Steve Rolston’s terminology, isolation was compromised, thus collapsing the experimental setup.

I pushed on this from what Dr. Phillips said. He pointed out that a superposition collapsing went from a quantum probability state (determined by something called phase) to a normal quantum state. I pointed out that this suggested that superposition was a non-random state. And, of course it isn’t. If you examine the double slit experiment the statistical pattern is, in fact, non-random. Each point on the interference is random but the statistical population as a whole is non-random.

Contrast this, then, with the “interference pattern” when the quantum state was lost. It was truly random with no interference pattern at all.  The loss of the experimental quantum state is called “decoherence.”

This whole discussion has been pushing me in the direction of those who are in the “shut up and calculate” school of quantum interpretation. If you move away from words “observer” and “measurement” and replace them with “loss of isolation” and “decoherence”, the sense of mystery goes away. There is still enough odd behavior, such non-locality or “spooky action at a distance”, to go around.

At that point my brain was full and I was ready to decohere. Besides, I had a non-random airplane to superimpose upon.

It's been a week since the conference and my head is still buzzing. (The whole flight back was a classical world model of quantum decoherence.)  It will be interesting to see how much will stick. How much will get refigured incorrectly as my brain tries to make sense of it.

The quantum physical model of the universe doesn't have a lot of commonality with the classical world. It reminds me of something in A. E. Van Vogt's Rogue Ship. The main character is expounding on physics above and below the speed of light. He considers physics above the speed of light reality and below the speed of light an illusion.

AEVV's grasp of physics was tenuous at best. But he did present an interesting dichotomy between what we think of as normal and what normal actually is. Quantum physics and relativity are the real thing. We happen to live in a region of velocity and energy where the consequences of reality aren't readily apparent. Consequently, we take our provincial point of view and consider it the real thing.

Bill Phillips (and others) suggested that superposition was analogous to a Necker Cube

This illusion of a three dimensional cube can be viewed as projecting outward from the page or inward from the page. Your eye can view it either way but not both. Yet both are present in the illusion. Think of superposition like that.

But I think there's a deeper metaphor here.

The Necker Cube is not a cube. It's a collection of lines in a flat space that represent a cube to our limited perception. The fact that our eyes and brain can make a cube out of it at all shows how we force that limited perception into areas where it does not fit.

I think the physics of the universe is truly wonderful. But the appearance of  strangeness is a product of our limitations.

Our brains evolved out there on the savannah trying to figure the best way to hunt food and attract mates. It's an accident that we turned out to be smart enough to detect a glimmering of the real world.

The universe does what it does. We just have to learn to catch up.


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