Wednesday, December 25, 2013

Plain English arguments for quantum computers

MIT professor Scott Aaronson is forever trying to explain the wonders of nonexistent quantum computers, and now he tries with only common words:
You might wonder, why is it so hard to build these new computers? Why don’t we have them already? This part is a little hard to explain using the words I’m allowed, but let me try. It turns out that the new computers would very easily break. In fact, if the bits in such a computer were to “get out” in any way — that is, to work themselves into the air in the surrounding room, or whatever — then you could quickly lose everything about the new computer that makes it faster than today’s computers. For this reason, if you’re building the new kind of computer, you have to keep it very, very carefully away from anything that could cause it to lose its state — but then at the same time, you do have to touch the computer, to make it do the steps that will eventually give you the right answer. And no one knows how to do all of this yet. So far, people have only been able to use the new computers for very small checks, like breaking 15 into 3 × 5. But people are working very hard today on figuring out how to do bigger things with the new kind of computer.

In fact, building the new kind of computer is so hard, that some people even believe it won’t be possible! But my answer to them is simple. If it’s not possible, then that’s even more interesting to me than if it is possible! And either way, the only way I know to find out the truth is to try it and see what happens.
Does that sound as it he is on track to prove something possible? Not to me. I am among those who believe it will be impossible, and I am very skeptical of the supposed progress.

He also argues that P != NP because verifying a proof ought to be much easier than finding an original proof. That is a reasonable argument. If it turns out that P = NP, then we would have to revise a lot of what we think about complexity, so we should be very skeptical of any such claim. Likewise we should be skeptical about quantum computing.

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