A non-running computer produces fewer errors

New Scientist magazine (February 2006, page 21) | 23 Feb 2006 | Edcoil

[Physicist]

Aha, but the apparatus can be enlarged to comprise many paths, cutting down the probability of a detonation to effectively zero. And really, who needs the Nuclear Test Ban Treaty, anyhow?

[Doctor Stochastic]

And really, who needs the Nuclear Test Ban Treaty, anyhow?

The Haves.

[stylin_geek]

I guess it depends on what the meaning of "running" is.

[antiRepublicrat]

I've had several graduate quantum mechanics classes and still don't get this.

I think anyone who does claim to fully get quantum mechanics is lying.

[antiRepublicrat]

I mean, it's only F---ING MAGIC THAT WORKS.

That's the best way to describe quantum mechanics I've heard so far. Thanks.

[tubebender]

I may have to rethink my tag line...

[KayEyeDoubleDee]

A non-running computer produces fewer errors,

What is the explanation for this statement?

[KayEyeDoubleDee]

I haven't thought about this too hard, but why doesn't a good bomb act like an observation, and collapse the wavefuntion prior to points C or D?

[operation clinton cleanup]

And now researchers from the University of Illinois at Urbana-Champaign have improved on the original design and built a non-running quantum computer that really works

Guess the H.A.L. program didn't pan out...

HAL became operational on January 12, 1997 (1992 in the movie) [1] at the H.A.L. Laboratory in Urbana, Illinois, and was created by Dr. Chandra

[Physicist]

I haven't thought about this too hard, but why doesn't a good bomb act like an observation, and collapse the wavefuntion prior to points C or D?

It does...and that's precisely why this scheme works!

In the "dud" case, there's no measurement, so there's a superposition of paths: the single photon takes both the clockwise (or upper) path AND the counter-clockwise (or lower) path. The two superposed wavefunctions cancel at C and constructively interfere at D.

In the "good bomb" case, there is a measurement, as you point out: either the bomb goes off, telling you it took the counter-clockwise (lower) path, or it doesn't, telling you it took the clockwise (upper) path. Those two possibilities are not superposed, so they can't interfere. The photon is forced by the measurement to take either one path or the other, but not both. But if it takes the pure clockwise (upper) path, it still has a 50% chance of being reflected to C by the half-silvered mirror in the C-D corner. So in 25% of the "good bomb" cases, you see no explosion, but measure the photon at detector C, which can never happen in the "dud" case. (50% of the time, the bomb goes off, and 25% of the time the photon ends up at detector D, which looks just like 100% of the "dud" cases).

[Physicist]

Ping.

[Physicist]

What is the explanation for this statement?

Just a guess--I haven't read beyond this excerpt--but if the errors in quantum computation are caused by decoherence within the system, then perhaps that is obviated by the system not actually performing the calculation. What counts here is the potential for the system to have performed the calculation. Again, just a guess.

[FreedomCalls]

I had someone from Diebold tell me that the results of an election can be ascertained with 100% accuracy even before the election takes place.

[Physicist]

Florida.

[Still Thinking]

So did the carpet match the drapes?

[TrebleRebel]

Actually, all the bombs explode - that is, in other worlds. According to the MWI, you kind of cheat the universe splitting, and you get to keep some good bombs that DID explode in another universe.