Hi all,
Lawrence Ioannou from Cambridge will be giving an additional talk
tomorrow 5pm in HIT J51 (sorry, I don't know why they gave us J floor
instead of K). Title and abstract below.
Cheers,
Roger
Universal quantum computation in a hidden basis
Suppose we are given several copies of a state |psi> that is promised to
be orthogonal to |0>, but is otherwise unknown. We consider the
quantum-information-theoretic tasks of state preparation and universal
quantum computation with respect to the "hidden basis" {|0>,e^{i
\theta}|psi>\}^{\otimes l}, of an l-logical-qubit system, for a random
\theta. We give an exact algorithm for state preparation, and give an
efficient approximation algorithm for universal computation. We apply
our results to quantum-public-key authentication protocols, by showing
that a class of digital signature schemes is insecure.