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.

Impact (contact) de l'Impactor de Deep Impact

Impressive picture of Deep Impact’s projectile hitting the comet Temple 1. The blow did more damage than expected. The photo was taken by the medium resolution camera on the spacecraft.

It’s often the unmanned spacecraft that yield the most interesting scientific results.

Image: NASA.

Avibase is a multilingual bird database with 1.9 million entries on 10,000 species and 22,000 sub-species. In case you need to know that the Black-crowned Sparrow-Lark is called Saharanvarpuskiuru in Finnish.

The French version of the home page makes me smile. When they ask you to enter a “nom d’oiseau”, this is meant literally (scroll down to the very bottom of the page).

If you live within regional public transport distance of Paris you can visit the Louvre the way you would explore a town or, if that is more to your liking, a shopping neighbourhood: just agree on a meeting place and time and decide on the spot what to do. This is a great privilege. Feeling […]

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Saturn’s rings

De belles photos de Saturn. D’ailleurs c’est qui, Cassini-Huygens?

  • 2004-07-04
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Last week, NASA and ESA’s Cassini-Huygens spacecraft crossed Saturn’s rings and entered the planet’s orbit. It is now sending us the most captivating and delightful images. Cassini-Huygens is going to fly by the moon Titan in October. Then, the Huygens probe will separate from the Cassini spacecraft and attempt a landing on Titan’s surface, scheduled […]

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