Back in 1998 a theory was posited that a computer built on quantum mechanics wouldn't have to run to work, thanks to the mysteries of superposition and Schrodinger's cat. Now the University of Illinois has built a system that proves the theory. Using mirrors and an undecided photon, they've gotten results even when the photon doesn't enter the system.
As New Scientist reports, 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.
Just to repeat what I think is a fascinating point, a computer built on this principle would not have to run to give answers. I can see a quantum computer working half the time, just as Schrodinger's cat would theoretically die half the time when the neutron decays. But this is more along the lines of the feline walking out hale and healthy in every test.
Not that we'll all be using quantum computers in the next year or two. As an article in Nature points out, the success of this one experiment does not translate into anything immediately useful. "The computer must still be programmed and turned on, even if it is not run, so the approach will not save on electricity bills or labour costs."
However, it is a significant tidbit of technology. Maybe it's not ready to revolutionize the world, but it will surely affect the future--even if it doesn't run just yet.
How does this development differ from what computers can already do while "off"? Notebooks and handheld PDAs have long been able to keep track of time and other information, even wake themselves up at pre-determined times. I understand that an "off" quantum-powered system would, theoretically, be nice... but what are the practical, real-world applications?
As I understand it (which isn't especially well, I've no background in quantum mechanics), a computer that can make use of the quantum properties of matter would be incredibly fast. But as both you and one of the articles in Nature pointed out, there aren't many real world applications. At this point. Given the pace of technological development, that'll change.
I dont really understand what you are talking about either and how it is any diferent than what computers already do. If you could further explain in a comment, that would be great.
This analogy will make computer science people groan, but you asked ;)
The standard computer is like a maze. Electrons are the rat, which goes through the maze and is shuffled around until it comes out somewhere else. A computer built using quantum mechanics would have a photon-rat instead of an electron rat, and photons move much faster. Furthermore, the rat wouldn't even have to enter the maze--people watching the rat would be able to figure out which way it would go if they let it into the maze, just by seeing how its whiskers quiver, which direction it's looking, etc.
So far the experiments have been very simple, just enough to prove what's doable. Presumably experiments will continue until they find a use for it, because speeding up computers is one of the high priorities in technology today.
Quantum Computers will be more then astronomically more powerfull then current computers. Why? because instead of bits that are on or off they have qbits that are on and or off at the same time and they can be entangled. When you add a bit to a normal computer it is a bit faster... add a qbit for a qcomputer it is doubled in it's power that adds to the possibilities in the pool of qbits it steps up what kind of problems you can tackle, which increase in an exponential way. I expect quantum computers will be up and running at full scale in less then a decade because every era is much shorter then the last. 250,000 years of agriculture 250 years of industry 60 years since the transistor 6 more years untill this works.