"Randomness in Quantum Computation," by Juan Pablo Paz. Science, 19 December 2003,pages 2076-2077.
Randomness is useful in many computational settings, so a natural question ishow randomness could be achieved in quantum computation. Paz summarizesresearch done by Joseph Emerson and others that is published in the article"Pseudo-Random Unitary Operators for Quantum Information Processing," beginningon page 2098 in the same issue. Although the "weirdness" of quantum theorycould suggest that randomness is easier to obtain in a quantum setting than itis in a traditional one, achieving randomness in quantum computation hasactually been shown to be exponentially hard. In the research article, Emersonand colleagues present a simple method for achieving near-randomness. They showthat their method converges very quickly to true randomness.
--- Mike Breen