Can someone explain this to me?

[matgb]

I know there are some physicists and other science types hanging around, this looks very cool, but it's way beyond my normal abilities to get the basics of science.
Quantum computer solves problem, without running

“In a sense, it is the possibility that the algorithm could run which prevents the algorithm from running,” Kwiat said. “That is at the heart of quantum interrogation schemes, and to my mind, quantum mechanics doesn’t get any more mysterious than this.”

From jackthomas

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Comments

[silentgreeneyes.livejournal.com]

Ok.. my only response is 'what the fuck?'

I know quantum stuff in physics is generally odd.. but this seems completely against logic.
Oh well, if it works it works :)


The bow-tie on the guy in the photo though is scary o_o

[johnwordsworth.livejournal.com]

I think the theory behind the article is related to the Negative-Result experiment idea (Reninger's maybe?). Anyhow - the basic theory being, you can often infer a truth purely because something HASN'T happened.

Example. Something radioactive is about to decay and fire out some radiation. If you have 2 detectors for left and right (hemispheres - so it HAS to hit one), then you only need to read data from one of the two to find out exactly what's happened. If you read nothing, you can deduce it's gone the other way.

Now, applying this to the algorithm in the article (probably in a very bad/crappy way), I think this basically means... You have a photon. You have 4 records in a database which refer to 4 'places' that photon can be. You have an algorithm which 'places' that photon on a path through the correct place/record. If the photon doesn't go to one of those places, the record you're looking for obviously isn't there. Also, if you can tell which way the photon is going to go before it goes, you can tell which record it's heading towards before it gets there. ie. Before it's even run the algorithm, you know where it's going.

That might be completely wrong, but that's what I get from the article, and there might be a mote of truth in what I've said. Maybe.

[poifaerie.livejournal.com]

In the equivalent of monosyllabic words...

A photon can be considered as a particle or a wave, or both at the same time, or neither (like liquids have properties of solids, gases, both and neither all at once). The particle bit can be considered to be in one state, or position, and the wave bit in another state or position while the photon is in both but yet neither states... with me so far?

There are lots of routes the photon could take through the algorith to reach an answer (like there are lots of routes through a building to get to a certain room), but they need only detect it in one position of one state to know where it it heading. So by superpositioning a photon is states of 1 and 0 (ie "run program" and "don't run program",) physicists are a very clever lot who can take a small amount of information (the position and state of a certain photon at a certain time) and extrapolate to find the large answer.

Does that help?

[matgb]

I think that now makes sense to me.

I was going to study physics, but the school was crap, I dumped the subject when we realised the teacher (for A level) had to check the text book several points during a lesson. It was either switch school or subject; school was 5 minutes walk, so I took history instead.