Diacritiques

Now that’s certainly a paradoxical term; it even sounds vaguely self-contradictory. The underlying facts are just as surprising:

By combining quantum computation and quantum interrogation, scientists at the University of Illinois at Urbana-Champaign have found an exotic way of determining an answer to an algorithm – without ever running the algorithm.

Using an optical-based quantum computer, a research team led by physicist Paul Kwiat has presented the first demonstration of “counterfactual computation,” inferring information about an answer, even though the computer did not run. The researchers report their work in the Feb. 23 issue of Nature.

Further down, Paul Kwiat gives a slightly clearer definition of counterfactual computation in the context of quantum computing :

“It seems absolutely bizarre that counterfactual computation – using information that is counter to what must have actually happened – could find an answer without running the entire quantum computer,” said Kwiat, a John Bardeen Professor of Electrical and Computer Engineering and Physics at Illinois.

Should you have online access to Nature, you can read the article.