Wednesday, December 13, 2006

Doggerel #17.1: "Quantum" (Take Two)


This updated edition of "Doggerel" brought to you by Infophile.


Welcome back to "Doggerel," where Bronze Dog rambles on about words and phrases that are misused, abused, or just plain meaningless. This week’s going to be a bit different, though. We’re returning to a subject that presents a most interesting problem: Quantum Mechanics. Richard Feynman explains it best:

“I think I can safely say that no one understands quantum mechanics.”

And there’s the problem: Bronze Dog isn’t “no one,” so he can’t come out here and explain it. I, on the other hand, am different. In order to facilitate the help I’ve given the Canadian Special Forces (Never heard of them? That’s how good they are), the Canadian government has officially registered “no one” as one of my identities. This means that when someone comes up with a code that “no one” can crack, I can crack it. Or maybe if “no one” can tell the difference between butter and I Can’t Believe it’s Not Butter, I can. I also understand Quantum Mechanics (henceforth “QM”).

The big problem with QM is that it’s in many ways counter-intuitive. Effects are somewhat non-local. Conservation of Energy can be temporarily ignored under the right circumstances. Particles act like both particles and waves at the same time. The results of experiments aren’t deterministic, but instead based on probabilities. And with all this, scientists still can’t agree on what causes all of this odd behavior.

There are two key ingredients here, QM being weird and scientists not knowing everything about it, which make “quantum” a very appealing word for woos to use. They figure that it gives them carte blanche if they explain any weird effect away as being “quantum.” It’s not just an “energy field,” it’s a “quantum energy field!”

Of course, they don’t understand it themselves most of the time, so in the end, it’s no better than hand-waving it away as “magic.” In fact, it’s worth noting that in Terry Pratchett’s Discworld novels, where magic is a well-understood force of nature, the use of the term “quantum” in explaining what counts for woo in that universe plays exactly the same role that the term “magic” does in ours.

The logic the woos use to defend their claims boils down to asking how, if scientists don’t understand Quantum Mechanics, they can claim the woos are wrong about it? It’s simple, really. Scientists are confused about what causes all of this, not what can happen. The possible events in QM are all well-defined, and the calculations of probabilities are done deterministically.

Now, there’s one particular phenomenon of QM, which the woos (particularly “psychics”) seem to love, that bears special mention here: Entanglement. In the simplest sense, entanglement means that there’s a correlation between two different observables. Remember that in general, measurements in QM have random outcomes. When two particles are entangled, measuring just one of them will still have a random outcome. But if you measure both at the same time, they’re outcomes will be related somehow – they might both always have the same outcome, always opposite outcomes, or simply tend more towards one of these extremes.

These effects occur regardless of distance between the two particles, so it seems like there’s some information traveling from one to the other, telling it what it should resolve as, at faster than lightspeed. This apparent transfer of information has made entanglement seem like a good way to explain faster-than-light communication for bad Science Fiction writers. Some woos also use it to explain telepathy by claiming the psychic’s thoughts become entangled with those of the subject.

It doesn’t quite work that way, however. Let’s go with a metaphor for entanglement: two magical entangled coins. These coins have the properties that their flips are always perfectly random, and if they’re both flipped simultaneously, they’ll always both come up the same way. So, let’s say that we have a human colony many lightyears away we wish to communicate with. We keep one coin with us, and the people going over there bring one coin with them.

Now, how would we use these coins to communicate with them? You could try to receive data by flipping your own coin, but all you know from it is that if someone’s flipping it at the colony, they’re getting the same results. You could try to force the coin to come up one way, in hopes of sending binary information, but the first property of the coin prevents this: Its flips are always random, no matter what you try to do. In the end, all you can possibly get from this coin is logical inference about the other coin. There is an instantaneous transmission of information between the two, but the data that’s transmitted is completely random and can’t be forced.

The way psychic apologists use entanglement requires a different rebuttal. They can actually get around the above restriction if they claim they claim that conscious thoughts are generated in part by the random outcomes of quantum processes (which some bona fide scientists are theorizing). In this case, if part of the psychic’s mind is entangled with the subject’s mind, the same thoughts will be randomly generated in both. The problem in this case is that there’s no reason the two minds should have become entangled in the first place. Entanglement between two particles happens due to a close, quantum-scale interaction between the two. You can’t just magically turn on entanglement with someone who’s far away from you.

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12 comments:

Tom Foss said...

Sadly, this post could go on for pages and pages, detailing how woos misuse superposition and mangle uncertainty to vaguely support their crazy ravings. Very nice summary, though!

Berlzebub said...

Excellent post Infophile. I've had a vague understanding of QM, but this makes it quite a bit clearer. I realize it's a watered down version, but that's what I needed.

-Berlzebub

Anonymous said...

Actually I can think of a way to use the coins to communicate. When you flip the coin it can land heads or tails but there's a good chance of the coin will not land with the same side up as previously. So while we can't say which side will land when we flip the coin, over a certain number of flips we can pretty much guarantee that there will be a reversal (say we flip said coin 10 times in 30 seconds). So in each block of 30 seconds we either are flipping the coin, which would show up as the occasional reversal, or not flip the coin, which wouldn't do anything. Then we can assemble this into binary. Obviously, the more flips per unit time the better.

Garrett (I have too much time on my hands)

Bronze Dog said...

In short, communicating by flipping the coin in spurts and not flipping the coin. Trippy.

Infophile said...

(Blogger isn't letting me sign in for some reason; probably because of the Beta switchover. My apologies if this comment shows up multiple times.)

Berlzebub: If you want to go a bit deeper, I've started a series on my own blog, Quantum Mechanics for Dummies, where I'll try to explain various aspects of QM so anyone with some basic knowledge of science can understand it. There's only one entry so far, but once school settles down, I'll continue with it.

Garrett: I don't think that will work. Let me go over your suggestion in detail:

When you flip the coin it can land heads or tails but there's a good chance of the coin will not land with the same side up as previously.

There's a precisely 50% chance it will not land with the same side up as previously, and a 50% chance it will. You seem like you might be straying towards the Gambler's Fallacy here.

So while we can't say which side will land when we flip the coin, over a certain number of flips we can pretty much guarantee that there will be a reversal (say we flip said coin 10 times in 30 seconds).

True, in the same sense that in a long period of time we can guarantee there'll be at least one head or one tails. However, note that if we flip it 10 times, there's a 1/512 chance of no reversals.

So in each block of 30 seconds we either are flipping the coin, which would show up as the occasional reversal, or not flip the coin, which wouldn't do anything.

So, how would the other people know whether you're flipping the coin or not? Remember that to them, if they're flipping the coin constantly, they'll see a typical random binary distribution. You flipping it or not flipping it won't affect their distribution, but when you flip it you see the same distribution they do.

Here's another way to look at it: Behind the scenes of the universe, there's a "God Coin." The God Coin is flipped once every three seconds, without fail, and has a perfectly uniform distribution between heads and tails. When either of our entangled coins is flipped, it will always have the same result as the God Coin's flip during that 3-second window. From this scenario, it's apparent that flipping one coin won't affect the other in any way, but instead the same source is causing both to have the same outcomes at the same time.

Now, in reality it doesn't work quite like this. The main problem is that as soon as you measure a particle, any entanglement it had is lost. So, for any pair of entangled particles, you could guarantee you'll get correlated results with the other observer if you both measure the particles at the same time, but after that you'll see no more entanglement between the particles. You can, however, simulate our many-coin-flips scenario if you send a large number of entangled particles to each location, and measure each pair together, one pair at a time.

TheBrummell said...

I also have too much time on my hads.

What if our two hypothetical entangled-coin-communicators based their signals on pre-arranged patterns and codes?

Imagine that they've agreed to both flip their respective coins at a particular time, each and every day (let's ignore for the moment [yes I'm being bad] the time-dilation effects of interstellar travel - perhaps their time signal is a regular normal-light-speed pulse from a very distant pulsar that reaches both colony and homeworld at the same time, or something).

OK, so they both sit down with their coins at 10:00 am on Monday, and flip five times in a row, recording the results. Then they compare their sequence (eg H-H-T-T-H) to their code-book, which they both have identical copies of.

For the purposes of my strained example, let's suppose that H-H-T-T-H means "space monster attacking!". But how did they colony send that signal on purpose? The coin flips are random.

So to confirm the signal, both colony and homeworld flip their coins three more times. If they get any result other than H-H-H, it's assumed the previous signal is a mistake, and they'll try again.

Essentially, both parties continue flipping their coins until they get a long sequence (of corresponding low total probability) they're happy with.

I don't know if this would really work, or how time-consuming this would be. But I enjoyed thinking about it, and reading this post. Thanks.

Infophile said...

So, the question becomes: how are they forcing the results? Neither of them has any control over how the coin flips resolve. All that will happen is that eventually they'll both randomly flip H-H-T-T-H then H-H-H on the same day, and both panic needlessly.

Joshua said...

On the other hand, there is very real research into communications using quantum effects. It will probably happen eventually, though it probably won't work anything like how woos and sci fi writers think it will.

I mean, I'm not too sure about FTL comms, but there is quantum cryptography, which actually does communicate using entanglement.

The better argument for countering psychic QM is simply that our brains are too big and that all the atoms are tied into bigger structures that are pretty well-described using biochemistry. It's actually for the most part rather classically well-behaved. QM effects typically are observed only at a small scale in experiments specifically set up to examine QM.

Check out the WP article on quantum cryptography.

I'm not refuting the main point of the post in any way, since it's entirely clear to anyone with a brain that most woo explanations that involve quantum mechanics are spouted off with no justification by the utterly ignorant, but any off-hand dismissal the idea of using QM for communications is unfounded. There very well could be a way of using QM for FTL communicatons, we just haven't found it yet.

Infophile said...

I mean, I'm not too sure about FTL comms, but there is quantum cryptography, which actually does communicate using entanglement.

Oh yes, I wouldn't forget about that - I'm doing my research project on it after all. I just couldn't find room to fit it in, and figured a caveat like that would be better mentioned elsewhere.

But for those wondering right now what that is, basically we send groups of entangled particles to two people: the sender and receiver. These particles are ordered, so they can measure them and get a random binary string. They'll both have the same string, of course. This string is then used as the key for encryption of a message which is sent through standard channels.

The benefit this has over standard encryption is that if the key is intercepted, there's no way for the interceptor to send a copy of the key on to the receiver. They could try, but the results can't be forced, so the receiver would end up with a different key. Then when the sender sends a test message and the receiver can't translate it, they can broadcast an "Abort" before sensitive information is sent. Using entanglement this way, we can all but ensure that codes can never be tracked.

Anonymous said...

That encryption string idea is brilliant... could you use it as a better way to attempt to explain apparently "psychic" events?

For example, imagine a case where a psychic claims to be able to provide information about a person from an object or photograph. Could they be somehow observing groups of particles that originated at the last point of contact with the object or the moment the photo was taken?

Just a thought :)

Bronze Dog said...

The problem with "psychic" events is that they've got very mundane explanations. I suggest you visit randi.org and skepdic.com for some of them. No need to force QM into fitting mild oddities that turn into mundanities.

Ron Murphy said...

In addition to the specific answers above that are given in terms of QM, even if brains could be 'entangled' in some macro sense, then they'd be entangled with all brains, and consequently there would be too much noise to pick-up anything useful. Even worse, there would be so much internal 'entanglement' between particles inside a single brain it would swamp any information from other brains.

Not only is there no understanding of QM, but neither is there any understanding of consciousness and what 'thought' is. There's never any explanation of a mechanism that can be demonstrated.