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View Full Version : Which will come first - DNA or Quantum computer?



Tinaa
2005-Dec-29, 03:36 AM
I'm reading a spy thriller by Ludlum about a DNA computer that gets stolen by terrorists and they are causing havoc all over the world.

This made me curious about DNA computers which led to reading up on them. Very simple DNA computers have been made, but require human action to work. Here is an example: http://news.nationalgeographic.com/news/2003/02/0224_030224_DNAcomputer.html

I also look up a bit of info on quantum computers, which I found was mostly over my head. http://www.carolla.com/quantum/QuantumComputers.htm
I get the basic idea, but...

Which is the better computer? Which will come first? How will we use them?

snarkophilus
2005-Dec-29, 07:20 AM
I'm reading a spy thriller by Ludlum about a DNA computer that gets stolen by terrorists and they are causing havoc all over the world.

This made me curious about DNA computers which led to reading up on them. Very simple DNA computers have been made, but require human action to work. Here is an example: http://news.nationalgeographic.com/news/2003/02/0224_030224_DNAcomputer.html

I also look up a bit of info on quantum computers, which I found was mostly over my head. http://www.carolla.com/quantum/QuantumComputers.htm
I get the basic idea, but...

Which is the better computer? Which will come first? How will we use them?

Ooh! I didn't know they'd actually made DNA computers... I had that idea several years ago, but it looks like I was scooped. *sigh* ;)

Anyway, which is better depends on the problem size.

Reading the DNA article, the objections they list at the bottom of page 1 are pretty trivial. One page 1, it appears that they intend to do something equivalent to a Turing machine. That means that a DNA computer will be equivalent to the computer you're using now, but with something like 10^20 processors (whatever number you want, really) running almost simultaneously. On page 2, it's like they want to do something resembling a quantum computer (which kills your question except for the detail of which technology actually implements the idea first, so I'll assume it's not this).

Quantum computers are different beasts entirely. Quantum computing theory has a completely different set of algorithms and run times than conventional computing. For many problems, what would take (k*2^n + some smaller stuff) time (for some n related to the input size) on a conventional computer will take only some polynomial (k*n^a + some smaller stuff) time on a quantum computer. There is always a point where the 2^n function becomes bigger than the polynomial, and that's the point where the quantum machine is better.

So for very large problems, use a DNA computer. For very, very large problems, use a quantum computer. For instance, if you wanted to factor a number around 10^30, you could do that with a DNA computer reasonably quickly. But if you wanted to do something near 10^50, you'd be out of luck. On the other hand, the quantum computer might be relatively quite slow at 10^30, but relatively fast at 10^50.

Which will come first? I'd say quantum computers are closer to being used in homes. No reason for it, but I've seen a lot more research into the idea, and they have some small working ones (they recently factored 15... woo hoo!).

How will we use them? The same way we use computers now: primarily for porn and genealogy. And video games. And talking about science.