

New SciAm Article on Limits of Quantum Computing - rw
http://scottaaronson.com/blog/?p=309

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sarosh
For the impatient, a draft version in PDF format is available at
<http://www.scottaaronson.com/writings/limitsqc-draft.pdf> [pdf]. I
particularly enjoyed the somewhat applicable reference to Star Trek, humpback
whales and plexiglass.

"Contrary to the popular image, their work has revealed even a quantum
computer would face significant limitations. In particular, while a quantum
computer could quickly factor large numbers, and thereby break most of the
cryptographic codes used on the Internet today, there’s reason to think that
not even a quantum computer could solve the crucial class of NP-complete
problems efficiently. This class includes the problems mentioned above.
Limitations of quantum computers have also been found for games of strategy
like chess, as well as for breaking cryptographic hash functions. All of these
limitations apply to a class of algorithms known as “black-box algorithms,”
which encompasses all quantum algorithms known today. Giving a complete proof
that no fast quantum algorithm can solve these problems is out of the
question, since we can’t even prove that no fast quantum algorithm can solve
them. "

Although I do not follow Mssr. Aaronson's work, I keep bumping into his blog
often. Thanks for the heads up.

~~~
yters
For any kind of adversary system, the opponents will both use quantum
computers, so the effects will cancel out. E.g. quickly factoring large
numbers means the security industry will use larger numbers.

However, this is a problem for systems that are embedded and hard to replace.

