>>>>For anyone following the latest news on quantum computers, the following is quite interesting:
>>>>
>>>>http://www.physicsweb.org/articles/news/9/12/1/1
>>>>
>>>>( For more general information on quantum computers, see www.qubit.org )
>>>
>>>Thanks, Hilmar. I wonder how long it will be before any of this translates into a useful device. The subject has a strange fascination for me, although I really don't understand it. I wish I had the time to study this further, and qubit.org looks like a great place to start - it's one of the best organized and written, focused scientific sites I've ever seen.
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>>I was reading some of this to my 12-year old son yesterday, and he found it to be quite crazy. After all, how can a cat be alive and dead at the same time??? And after that, it becames only weirder.
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>>But that is more or less what quantum mechanics claims - that a quantum system can be in a superposition of several states, in a sense that is not normally observable in the large-scale world.
>
>IIRC, what Heisenberg was saying was that determinate systems have no meaning until observed. For instance the idea of an electron orbit is meaningless unless and until we observe it. It's when we try to bring that thinking into the macro world (the Schrödinger's cat, for example) that is becomes unwieldy. If you talk to a person with no scientific interest about electrons and the uncertainty principal, you'll generally get a bit of a head-shake, but acceptance. If you talk to that same person about the cat, they'll simply think you're nuts.

I guess what intrigues me about quantum computing is the prospect of seeing some new, macroscopic manifestations of QM. Somehow, despite the overwhelming confirmation of QM at the microscopic level (which indirectly has very observable macroscopic consequences), it is difficult to grasp at an intuitive level.

The properties of liquid helium may be the closest thing to a directly observable quantum behavior, for those few who are lucky enough to have played with it. But a quantum computer performing a useful computation would be a major revelation. The consequences for cryptography, among other things, could be dramatic.