Thursday, August 4, 2016

The Schrödinger Sessions: Day 0 and Day 1

(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 0
Got on the plane and got into Reagan. Took the Metro up to College Park and walked the rest of the way to the dorm where I was supposed to check in. Two miles in 95 degree heat. Not so bad if you kept moving and drank water and tried really hard not to think about it at all.

But I was thinking the whole way about this seminar. Was it going to be fun? Was it going to be boring? (How could it be boring I ask myself? Lots of ways I answer.) I pray for air conditioning in the dorm.

Prayers answered. I get something to eat and talk with a number of people. Several people come from Missouri. One comes from Western Massachusetts. The rest come from a lot of places. One woman writes for the television show The 100. Another is a best selling self published author. Another writes children’s books.

I think this might be fun.

Day 1
Introduction to Quantum Mechanics. A lot of history of why QM was necessary.

First, we all went back to Rutherford and spectroscopy. This was one of the first indications that light was packaged in discrete components. The distance between the spectral lines of an element turned out to be a relationship between the wavelength and an integer equation--  this was important. The fact it was an integer meant that there were discrete quantities.

Max Planck was trying to solve black body radiation issues. Black body radiation is the light emitted by an object because it’s hot—think of the red on an electric stove element. There was a relationship between the light emitted, temperature and frequency. From this, he derived Planck’s Constant. Einstein came along and related it to energy, deriving the equation:

E = hf

Where E was the energy emitted, f was the frequency of the light and h was a constant he came up with to make things right. The use of frequency tied the energy emitted to discrete values. This also became pivotal in his understanding of the photoelectric effect, special relativity, etc. You start seeing Planck’s Constant everywhere. De Broglie and the wave length of matter, the Bohr Atom and finally Schrödinger’s Equation:

From here.
(Discussions of Schrödinger’s Equation can also be found here.)

One of the critical things to notice is that little i: i is a utility in math. It means the square root of a minus one and is something that can't be observed in nature. Consequently, if you're looking for psi (the squiggly Y shaped thing) you can't solve for it without having an i in the result. The solution is to look for psi squared-- which takes the square root out of the equation. But that turns this equation into a probabilistic equation instead of a deterministic one.

This causes us to think of particles not as things but as something like a beat resonance in a set of waves. And there’s always the Uncertainty Principle.

Now, we start getting into the weirdness of double slit experiments. These are experiments where a light is shown through a close pair of thin slits and the interference pattern is observed. Interference patterns are wave functions. But light shows particle nature—systems can be built to emit single photons of light that, when going through the slit, show up as interference patterns. It is as if the photon doesn’t know which slit it’s going through or, perhaps, goes through both. I.e., it shows both wave and particle nature at the same time.

It gets even more interesting. “Observing” which photon goes through which slit destroys the interference pattern. Even more, setting up to observe which slit the photon goes through destroys the interference pattern even if the actual observation doesn’t occur.

Steve Rolston suggested a different way to look at this whole observer/measurement stuff. Consider the experimental system as isolated from the rest of the universe in order to precisely observe a specific behavior. This is not unusual—after all, scientists isolate systems for study all the time. The act of “observing” or “measuring” in a particular context breaks that isolation and destroys the delicate environment in which the experiment takes place. I.e., the words “observer” or “measurement” imply an intimate and mysterious connection between the humans and the cosmos. However, if the nature of the experiment requires a specific kind of isolation, the breaking of that isolation can destroy the behavior being studied.

It takes an unnecessary mystery out of quantum physics. It's weird enough already.

Then, we went into metrology: the study of measuring. This involved some entanglement—not enough. I didn’t get enough—but more importantly, a study of Bose-Einstein Condensates.

De Broglie came up with a relationship between the wavelength of a particle and its energy. As things are cooled, the energy is reduced. As the energy is reduced the size of the wavelength approaches the distance between the particles. When these get close enough, the Bose Einstein Condensate is formed. These are particles that have the same values for the Schrödinger’s Equation.

At this point, quantum phenomena show up at macroscopic scales. Superfluidity, superconductivity and other qualities show up.

After this, we got to talk to one of the scientists on the LIGO project.

Gravity waves are cool.

End of Day 1.

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