ETH Zurich researchers have developed a method that guarantees complete randomness in a flow of information. The researchers, led by Roger Colbeck and Renato Renner, wanted to better understand the role of randomness in quantum theory. The researchers calculated what might happen to a stream of partially random information, in which some of the bits are correlated with other variables, thus making the bits non-random. The researchers used these bits to choose measurements on pairs of entangled particles sent down two different paths, which produced an outcome that is independent of any other variables, according to Colbeck and Renner. "Imagine an adversary who can guess at what choice you're going to make at a given time," Colbeck says. "Now we've shown there's a procedure where you can make it so the adversary cannot guess at all, within certain limits. In principle, one could use this to make better quality random numbers." The ETH Zurich researchers may next explore precisely how non-random the information flow can be and still be transformed into a purely random stream. "The fact that the quality of randomness can be improved is new and surprising," says University of Geneva physicist Nicolas Gisin.

From "Physicists Go Totally Random"
Science News (05/06/12) Alexandra Witze
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