Quantum Computer Works Better Shut Off 376
waimate writes "A New Scientist article relates how its possible to get answers from a quantum computer even when your program isn't running." From the article: "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."
Misleading (Score:5, Informative)
Does anyone know what is new here ?
Schrodinger's running cat (Score:2, Informative)
Now they replaced the inhumane process of killing cats with just letting the cat hit Enter to run the program (instead of killing it). So now instead of "somewhat" dead cat you have a program that is "somewhat" runnning.
Re:Black Magic (Score:5, Informative)
Nature (Score:3, Informative)
http://www.nature.com/news/2006/060220/full/06022
http://www.nature.com/nature/journal/v439/n7079/a
IANAP, but I'll try to explain... (Score:5, Informative)
Someone else already posted an useful background URL with is a good place to start:
http://en.wikipedia.org/wiki/Elitzur-Vaidman_bomb
Basically, what you have here is something called "interaction-free measurement". Because of the quantum mechanics work, a particle's wavefunction evolves in a certain way over time, which then "collapses" when you measure it to something specific. How it evolves is not deterministic, but probabillistic. Because of this, you can set up a quantum system whereby when you place a certain object in it at a certain place, you can change the whole system given the nature of what you add to it.
In this case, you have a quantum computer composed of mirrors that runs on photons. The mirrors are pre-set in a certain configuration to run a certain "program". No electricity is needed to "run" the program; you just inject photons into it and it spits out results when you measure it.
What they've done here is then place that computer in a certain location in an existing quantum mechanical system, the one which the photon comes from. This photon is associated with its own set of mirrors and detectors, and because of where and how the computer is placed into it, it effects the larger system.
Thanks to QM, you can then tweak the exterior system so that the chances of a photon ever actually getting to the quantum computer are infinitessimally small. But because there's still a small chance, the very nature of the computer in that location allows you to determine the results it would generate, even though a photon never actually gets into it to "run" it.
So, it's not to misleading to say the program never actually "runs". And you could say the computer isn't "on", but since it's just a mechanical-optical construct it's always "on". More importantly, though, is that exactly where the "computer" is becomes blurred; while it's true that it's particular programming is self-contained, by hooking it up to the external quantum system, you're sort-of making it a part of the computer as well. The "work" is being done by the photons outside the computer; remove them and you don't get anything.
Wow, reading the above, I didn't really do a good job of explaining this at all. But basically, even though the quantum program never actually executes, you still need to create it, and you still need to put it in a certain spot so that its quantum effect on the world around it can still be measured, and from that, you can infer what the program would actually do.
Bruce
Horrible mangled article. Better one: (Score:3, Informative)
Re:You mean like us? (Score:2, Informative)
Re:You mean like us? (Score:3, Informative)
There's a neat book by a guy named Michael Talbot called The Holographic Universe [amazon.com] that talks about this idea quite a bit. He often cites David Bohm, and if you want to get into Bohm's thoughts on the potentially holographic nature of the universe and how that relates to us through quantum effects, you should read Bohm's Wholeness and the Implicate Order [amazon.com]. Bohm is/has been a leading researcher in the field of Quantum Physics.
In short form: Talbot's assertion is that some part of our brain operates like a hologram, with diffraction patterns caused by quantum fluctuations basically defining us, whether you are talking about thought or memory. Further, both Talbot and Bohm suggest that the holographic nature of our brain provides us a means to tap into a deeper holographic reality, which they both claim explains experiences with the "paranormal".
The counterargument is that quantum effects are not significant enough to affect, say, the firing of a neuron one way or another. I find this to be an extremely specious argument (but keep in mind, IANAQuantumPhysicist) since everything is connected, and the way we picture matter (in terms of being built of entirely divisible, discrete atoms) is really not very accurate. It's very newtonian - you push on this atom, and it pushes on that atom, but since we know that atoms don't actually touch each other, and there is a propagation effect involved... Well, let's just say it's hard for us to make concrete statements about things we don't really understand. And besides, physicists I know don't hold that opinion. It always makes me feel better when people smarter than I am hold similar views...
Re:Gee whiz (Score:3, Informative)
No, you can't run non-existent programs (i.e. those who have 0% chance of existing.) However, the quantum computer would be able to run a program that has a non-zero waveform. I'm assuming this computer would be similar to Discworld's Hex [wikipedia.org].