Wednesday, April 30, 2014

Science for the hard of thinking

I went to a lecture on quantum computers last Thursday, given by a famous Canadian molecular chemist.* Despite being a professional computer scientist, I know fuck-all about quantum computing, and I have to admit that this hour and a half did little to change that. I mean, I know probably 85 or 90 percent of the words this guy used, but I don't think he was using them right. I felt like I was listening to someone read Lorem Ipsum while they flipped through Powerpoint slides of B-2 bomber schematics.

I was in good company. Of the fifty people in the room, only one seemed to be following along, and he was clearly a vampire, which I consider cheating. (Tall and very thin, pasty and pale, indeterminate age, hair like Bill Compton, you do the math.) Two others recognized a concept and asked a question, but they were obviously grasping and we pitied them.

Computer scientists generally don't know much about quantum computing, even though it's supposedly our future, which makes it fun to bring up in faculty meetings and watch everyone try to fake it. In fact, the only people who know anything about this seem to be physicists or molecular chemists.

In spite of all that, I quite enjoyed the talk. Freed from comprehension, I was able to focus on the trivia I found interesting, and marvel at what science has become.

First, I think we should establish -- and I can't stress this enough -- that quantum anything makes no sense whatsoever, and quantum computing is no exception. I felt a lot like someone trying to imagine what bathrooms would be like if we were built inside out. So even when I found a familiar concept it was immediately inverted and set on fire. Under water. It sounds like quantum computers will not calculate things so much as tell us all the things we could calculate if we had that kind of time, and then pick the correct answer from a set that never existed.

I did get a few interesting (to me, at least) tidbits, though I couldn't begin to tell you how they relate to the topic, or even what the topic was, if I'm being honest. It all started with a thing called a neutron interferometer. The idea is simple really (clearly a lie, but always how they start these things).

This apparatus is machined from a single crystal of silicon that costs north of 50,000 Canadian dollars. After months of machining, it is practically guaranteed not to do anything useful. (Image from here)

First you take a single crystal of silicon** about the size of a football, and machine most of it away. The idea is to get exactly parallel surfaces that are precisely spaced and smooth to the atomic level. Since this is plainly impossible, almost none of them work. Apparently this guy has a cabinet full of these things that are good for nothing, but much too expensive to throw away. The fun part is that no one tells the grad student spending two years of his or her life creating this thing that it won't work. They let it be a surprise.

Recently someone invented a machine to address this issue of non-workiness. The part I remember is that it uses a single cut facet of a large diamond to grind away 6-8 angstroms (ten-billionths of a meter) of silicon on each pass. After (I assume) about a millennium, you will have a working interferometer. I got a mental picture of someone's engagement ring stuck in this gigantic laser-driven Dr. Evil death ray, but that may not be exactly what it looks like. If it works out, they expect the graduate student suicide rate to decline precipitously.

As you can plainly see in Figure 1, the hypothetical neutron does or does not go one way or another as it passes through each  blade. Once the non-existent particle passes through the apparatus, assuming it has possibly taken the path we have not observed until now, we will be able to tell something. I guess. Figure 2 shows the graph generated by the passage of the midi-chlorians through the aether. (Image from here)

The idea behind this thing is that you shoot an individual neutron (a ridiculous idea to begin with) at one end. The crystalline structure will cause the neutron wave form to deflect one direction or another. Because a magic crystal is stuck on one path, you will be able to tell something about which way the non-existent neutron went once you look at it and it starts to exist. Or something.

One more fun fact. These things are crazy sensitive to vibrations and temperature change, so they spent six years and a crap-ton of money building three spring-mounted nested rooms and a special table to eliminate virtually all external interference. About the time they finished, someone figured out that if you just add a couple of extra fins to the crystal thing, noise wouldn't be a problem, so the room is unnecessary.

The guy also talked about some lattice of carbon and chlorine atoms that I think was supposed to be the computer part. There was something about stable free radicals and electron spins effecting nuclear spins, but by then I was feeling lightheaded and it all gets a little fuzzy. I never did figure out how that part connects to the neutron cannon we started out discussing.

I probably shouldn't admit it, but I love this part of my job. Every day I get to talk to people who are doing crazy shit with government money that not a hundred people on the planet understand. There is not much of it that you can do in your garage anymore, and most people think the work is preposterous, but if we ever get our flying cars it will be because of these guys.

* I know, contradiction in terms, right?

** The stuff that Star Trek pizza monster was made of, not the stuff they put in boobs.


  1. I spent so much time on Wikipedia because of this post, and that, my friend, is fucking awesome. First, I need to fully understand the difference between bits and qubits - like I know that chocolate chip cookies and snickerdoodles are both cookies, but different kinds. I guess. Kind of. Hey, I'm learning.

  2. Yes please with the flying car -- and then I will teach 'those guys' how to have more fun. Sorry we missed each other in AR. I am ready for some of your Southern Gothic stories whenever you have the yen to tell them.

  3. Holy shit! This is brilliant! Someone once said (paraphrasing, and too drunk to be bothered looking it up) that any scientist that couldn't explain the work to an 8 year old was a charlatan.... Honey, you've done a nice job with this one! If you REALLY want to scramble your circuits? Go sit through a talk on quantum encryption! i had to PRESENT that one once... a lot of time on Wikipedia before i was able to extract enough basics to be able to do a cursory job of explaining it.

    for what it's worth, i know a lot about single crystal silicon. not the boob kind... oh, and even more fun? be the one sprinkling the money out and about on the Big Brains. why i love my job, reason #870...