[Robert J. Sawyer] Science Fiction Writer
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[CBC Radio One]

Science FACTion

Quantum Computers

Copyright © 2003 by Robert J. Sawyer
All Rights Reserved.

Nebula Award-winning science-fiction writer Robert J. Sawyer writes and presents a weekly science column for the Canadian Broadcasting Corporation's CBC Radio One.

The columns, which have the umbrella title Science FACTION: Commentaries from the Cutting Edge of Science, are produced by Barbara Saxberg in Toronto, and syndicated to local CBC Radio stations across Canada.

Recorded 23 June 2003

Host: Visit any online store, and you'll see all sorts of notices about how it's absolutely safe to type in your credit-card information. No one can steal it, the sites say, because the data is encrypted. And that's true — the data is safe ... today. But science-fiction writer Robert J. Sawyer's job is to look to tomorrow, and he sees a big problem looming there.

Robert J. Sawyer: We're used to thinking of computers as being lighting fast, solving any mathematical problem with ease. But actually, conventional computers are very slow if the math problem is complex. And that's been a good thing: we've been relying for years on this fact to encrypt credit-card transactions and the transmission of sensitive data over the World Wide Web.

Sound Effect: AOL's "You've Got Mail!" greeting

Almost all encryption methods are based on the fact that complex mathematical procedures are inherently time-consuming, even with computers.

For instance, a common form of encryption involves using a key number that is the product of two prime numbers multiplied together; prime numbers are those numbers that can only be divided by themselves and one.

Now, multiplying two primes together is easy, and a computer can do it very quickly. But doing the reverse — taking the number produced by multiplying two primes together and figuring out which primes were used to make it is much more complex. In fact, there's no easy trick to do it: you have to try, by brute force, every possibility.

The key numbers used in encrypting financial transactions often have 128 binary digits — meaning there are trillions of possible factors. It would take even our fastest computers billions of years to figure out by trial and error which two prime numbers were multiplied together to produce the key. Yes, that's right — billions of years.

But a stunning new kind of computer may soon change all that. Instead of attempting just one possible solution at a time, quantum computers work by trying all the possible answers at once. They use the bizarre ability of quantum entities to be both zeros and ones simultaneously to do this. So, whereas a conventional computer can take billions of years to factor a large number, a quantum computer can do it virtually instantaneously. And that means, as soon as we have quantum computers, we will see our old encryption codes broken, potentially leading to our financial institutions crumbling, and the e-commerce revolution grind to a halt.

Of course, mathematicians are working on developing new encryption techniques that will be impervious to quantum computers. These techniques will also rely on strange qualities of the quantum realm, and are collectively referred to as quantum encryption. What needs to be found are mathematical puzzles that are fundamentally unsolvable no matter how hard you try; even a quantum computer couldn't figure out the answers to such puzzles, and so they can be used as the basis for truly secure encryption.

Of course, quantum computers have all sorts of uses besides cracking encryption schemes; basically, they'll turn any long, tedious computing process into an almost instantaneous operation. Anyone who has ever used a computer drawing program, and waited many minutes for a complex illustration to be redrawn on the screen after making a change, can appreciate the need for the power quantum computing will give us.

But it's a race to see which will arrive first: the quantum computer, or the encryption methods that it can't defeat. Just in case it's the quantum computers that get here first, I'm keeping some cold hard cash in my mattress.

Sound Effect: Cash register ka-ching!

I'm Robert J. Sawyer.

More Good Reading

Other "Science FACTion" commentaries for CBC Radio
"2020 Vision" scenarios for Discovery Channel Canada
Media backgrounder on Rob Sawyer

Rob's novels Factoring Humanity and Hominids, which also deal with quantum computers

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