There is a paper just published today on the Los Alamos Nat'l Labs
preprint site (http://xxx.lanl.gov/abs/quant-ph/9905064) on how to
simulate arbitrary nonlinear quantum dynamics. They give examples of
existing systems where the effect has already been seen and then give a
general description of using feedback to make a quantum system behave
nonlinearly. They show that in such systems, distances between quantum
states are NOT preserved.
It was previously published (can't find it right now, but it's on the
same site) that if QM was nonlinear at all, one could do a quantum
search in log N time instead of sqrt N time.
If today's paper is correct, then it's just a matter of sufficient
technology to break ANY code with a known-plaintext attack.
--
Mike Stay
Cryptographer / Programmer
AccessData Corp.
mailto:[EMAIL PROTECTED]
