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Quantum computer works best switched off

* 22 February 2006
* From New Scientist Print Edition

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Even for the crazy world of quantum mechanics, this one is twisted. A quantum computer program has produced an answer without actually running.

The idea behind the feat, first proposed in 1998, is to put a quantum computer into a “superposition”, a state in which it is both running and not running. It is as if you asked Schrödinger's cat to hit "Run".

With the right set-up, the theory suggested, the computer would sometimes get an answer out of the computer even though the program did not run. 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.

They send a photon into a system of mirrors and other optical devices, which included a set of components that run a simple database search by changing the properties of the photon.

The new design includes a quantum trick called the Zeno effect. Repeated measurements stop the photon from entering the actual program, but allow its quantum nature to flirt with the program's components - so it can become gradually altered even though it never actually passes through.

"It is very bizarre that you know your computer has not run but you also know what the answer is," says team member Onur Hosten.

This scheme could have an advantage over straightforward quantum computing. "A non-running computer produces fewer errors," says Hosten. That sentiment should have technophobes nodding enthusiastically.
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http://www.newscientist.com/article.ns?id=mg18925405.700&feedId=online-news_rss20
 
So on a quantum computer I can play World of Warcraft without actually running the game? Sweet, no more logins and subscription fees.
 
Yes, but this would run on Quantum principles, so you could either raid MC, or know that you've raided MC and that you should boast it. But not both.

I guess Heisenberg hates you.
 
I don't get it.

Could someone explain it in plain English?

What exactly did the computer do?

If it didn't do anything, that'd be a bit hard to prove.

All the article seems to say is that they have managed to produce a computer that acts quirky when shut down and that they blame quantum mechanics.

How could a computer that acts without following causality be any LESS error prone than a computer that acts based on a FLAWED causality?

Bugfixing would have to be a bitch if the errors occur as randomly as the non-errors.
 
Ashmo said:
I don't get it.

Could someone explain it in plain English?

What exactly did the computer do?

If it didn't do anything, that'd be a bit hard to prove.

All the article seems to say is that they have managed to produce a computer that acts quirky when shut down and that they blame quantum mechanics.
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Not entirely. They had a setup of 'mirrors' into which they send a photon, which would be 'running' the program (in this case a database search). Now, instead of actually sending it through those components, they stop it from entering by continually measuring the photon. However, the photon does still influence the state in which these components are, and is influenced by them, so without actually entering, it can still produce a result.

How this could be possibly less error-prone is beyond me, though.
 
they can run the program without actually entering the photon into the mirrors which are the program.
 
that really makes no sense at all... if by running they mean, there isnt any electricity active in the device, then they are correct...

But, i'm pretty sure that as long as -anything- at all is happening, the device is by definition running, as in ... being active

and i CANNOT believe there are people that get paid to come up with this bullshit, could you please PLEASE do something thats actually productive on a technological basis?

What would come from this development? really? I dont get it
 
MethidParadox said:
and i CANNOT believe there are people that get paid to come up with this bullshit, could you please PLEASE do something thats actually productive on a technological basis?

What would come from this development? really? I dont get it
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"Bullshit" indeed. Quantum computers will revolutionize computing like no other technology ever has. Quantum algorithms were developed for problems that are believed to be unsolvable (or extremely difficult to solve) with a classic computer.

For instance, Shor's quantum algorithm for factorization of large integers has polynomial complexity, whereas non-quantum algorithms have exponential complexity. Anyone with even a passing interest in cryptography and security knows the implications of this. The entire modern cryptography is founded on the fact that no efficient non-quantum algorithms exist for factorization of natural numbers and calculation of discreet logarithms. For example, in 1999. it took a system of 292 state-of-the-art computers *five months* to factorize a single 155-digit integer. If we take into consideration that cracking the average asymmetric cryptosystem with a 1024-bit key would require factorization of a 309-digit integer, you can imagine cracking such a cryptosystem would take *years*. On the other hand, a system of quantum computers running Shor's algorithm would be done within minutes...

Another example is Grover's algorithm (which is precisely what they used in the example above, I believe) for searching an unsorted database. The best possible non-quantum algorithm for this task has linear complexity, meaning you have to search the database record by record until you find a match. Grover's algorithm, on the other hand, is quadratically faster (= much faster) and based on some super-nerdy quantum concept.

P.S. Just to illustrate how awesome modern cryptosystems are, I'll mention the so-called "digital seal", or rather its implementation in form of PGP (which is a security system used for e-mail protection). Ideally, if all computers in the world devoted their entire processing power to cracking a single PGP message, it would take about 150 x 10^15 years. That's 12 million times the current age of the universe! Pretty fucking impressive, eh? In reality, though, it would probably take much less, for various reasons.

It's still pretty much impossible, though.
 
So they are developing optical processing with a quantum process, concurently.

I was wondering when we'd get optics up and running for computing.
 
Wow, that's some confusing shit. I think now I know how my parents feel when I try to explain computers and role playing games to them.

Ratty said:
Shor's quantum algorithm for factorization of large integers has polynomial complexity, whereas non-quantum algorithms have exponential complexity
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...

My cat's name is Mittens.
 
After reading and thinking about this for far too long, I think the photon still went through, either if was a multi-dimension thing or a "second-wave" thing; it still went through.

Either the waveform is not breaking down, or is making it through somehow. I think it's a failure of how a human machine or human cannot observe or keep up with the speed of a photon. There has to be a lag, where it's not getting through.

I don't know, I may have my head up my ass. But I think some things are being ignored here (considering quantum physics requires you to have faith in one of the interpretations, I think I'm probably right.)
 
The tiny problem with computers doing something when they're technically not doing anything is: How do you control what they are (not) doing and when?

The notion of Schrödinger's Cat didn't exactly help either because that one is one of the most misunderstood experiments in history.
 
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