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Science FACTion
Quantum Computers
Copyright © 2003 by Robert J. Sawyer
All Rights Reserved.
Nebula Awardwinning sciencefiction 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
creditcard information. No one can steal it, the sites say,
because the data is encrypted. And that's true — the data
is safe ... today. But sciencefiction 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 creditcard
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 timeconsuming, 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 ecommerce 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 kaching!
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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