Tuesday, September 25, 2007

Don't Mind the Entropy

If you're right about this it's going to make global warming look like Y2K!

Oh, I'm right you can count on it. Take another look in the box.

One look was disturbing enough, thanks. But I still don't understand, what is it you say is happening?

OK, one more time, slowly. You know that around 2005 or so, people started using quantum effects to build computing devices. Quantum Cellular Automata, photonic random number generators, that sort of thing?

Yes, I remember the buzz about QCA, but didn't that stuff turn out to be a dead end?

It sure did, when Fuji and Stein published their paper on Direct Quantum Computation in 2010 everything else became obsolete overnight. DQC made the whole thing incredibly simple, and erased the line between classical and quantum computation.

OK, so what?

So, that was the beginning.

Fine, but the beginning of what?!

The beginning of the leak.

The leak?

Yes, the leak.

Just what is leaking?

So far as I have been able to figure out, entropy.

Entropy is leaking?

Yes, entropy from the quantum world is leaking into the classical one.

How does that work, exactly?

Look, we have always thought that things in our world, the classical world, could be random, right?

Sure. I mean of course things are random.



Nope. Things can be very, very complex--but it turns out, if I am right, they were never random.

I see... Actually, I don't see, what the heck are you talking about?!

OK, OK, let me explain. Take a coin toss. A fair coin, heads or tails, random right?




Yes. Let's say you have a perfect isolation box and in the box you have a fair coin and a precision coin flipper. Get it so far?


Now you also have a computer that, in principle, knows everything about the state of the box and content and can calculate exactly what will happen in the box. You following this?

I am... but I am not sure I like it...

OK, so you simulate the process of flipping the coin, and you really do it, in the box. The computer "knows" everything that is happening in the box, see?


Well, it isn't random, see?! Just very complicated. It appears random, but it always follows the laws of classical mechanics. 100% predictable.

Hmm. How does this explain what's it that box?

Well, that box was a similar experiment. I didn't expect it to work, in practice. I mean, it isn't very well isolated, but—well you've seen inside!

Oh... hang on... that box... that's Schrödinger's cat!
Yes, it is.

But, what happened to it!?

That's what I have been trying to tell you. We've got a leak and things are started to break.

Your entropy leak? How does it cause... that?!

Well, you saw how the coin toss wasn't really random?


Stuff in the quantum world is random, really random. Not just very complicated, totally random. That was the point of Schrödinger's gedankenexperiment. You can't know the state of the cat unless you look, because it depends on a quantum event. When you do, the wavefunction collapses and the cat is either alive or dead. But, with the leak... well... things aren't working.

Not working?! That may be the winner for understatement of the millenium. Let me get this straight... Normally, looking in the box would force the state of the cat to either alive or dead?

Yes, normally, observation brings the whole thing in the classical world. But there has never been anything in the math or physics to prohibit a superposition in the classical world, in fact it was a mystery that we never saw it.

Well... I would rather have never seen it, personally.

I'm afraid you'll need to get used to it. You are going to be seeing a lot more, if I am right. Here's what I have figured out so far. The quantum world gives rise to the classical world, somehow. That is, all the stuff we see here is dependent on an interaction between quantum and classical mechanics. Each plays a role. The complexity of the world is where they interface. And the DCQ stuff punches a hole in that, every time it is used. The real randomness of the quantum world leaks into the classical and makes the normal interaction weaker. We've had these things in everything from comm units to cars for what, 20 years now? It is starting to take a toll.

So you are saying that it observation isn't enough to collapse the wavefunction any more?

Yes, that's pretty much it. If you force the superposition, like with the cat, just looking isn't enough anymore.

This is very, very bad.

It may be worse that that, there's more.


Yes. In the 1980's Roger Penrose proposed that human consciousness was a quantum effect. The idea was supressed by the quantum orthodoxy, in spite of plenty of merit. If he was right...

If he was right then...

Then very, very bad may not even be close to correct.



Blogger Aryeh said...

I read the Quark and the Jaguar (Gell-Man), and he talks about quantum events de-cohering. Talking it over with a physicist friend, I came to the understanding that the resolution of the 'superposed' quantum states does *not* depend on an outside observer. Makes it a lot less exciting... .

Thu Oct 18, 10:33:00 AM EDT  
Blogger Yaakov said...

Well, the theory is far from law at this point. There are still many workers who are looking at the observer as necessary. The problem is such a view is very troubling to a materialist.

I suspect, though can't support rigorously, that we are on an asymptotic trajectory so far as understanding this is concerned.

I don't know where on the curve, though.

Thu Oct 18, 10:39:00 AM EDT  

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