[quote=“Avrom”][quote=“Big Fluffy Matthew”]A quantum computer basically works by doing different calculations in parallel universes, which is how subatomic particles can be in 2 places at once.
A bit has 2 possible states, 0 or 1; a qubit has some possible states, 0,1 or both at the same time, and niether. Or something.
I’m not making that up.[/quote]
A quantum computer has nothing to do with parallel universes. [/quote]
Well, yes and no. The “Many Worlds Interpretation” is a mainstream one. Also, Quantum Parallelism and some formulation of Quantum Mechanics (chiefly Feynman’s diagrams) seem to suggest (or can be interpreted as) particles evolve in many “universes” at once. All the possibilities interfere with each other, giving rise to quantum effect even when a single particle (that one would interpret as a “little ball”, localized somewhere) is used.
Spin is one possibility. There are many others, like atomic levels in trapped atoms and ions, NMR, color centers in diamonds, quantum dots, superconductive Josephson junctions and also photons. I, for example, work on optical implementations of quantum computational tasks.
It is true that particles are never in two places at once, 'cause particles are by definition localized. The problem is that what we call particles are really better described by a wavefunction (delocalized). It’s the discreteness (the “quantumness”) of the wavefunction interaction emerging from many phenomena that brings back the particle aspect of many system (their “granularity”).
The experiments you’re referring to have to do with a phenomenon called “entanglement”, which Einstein referred to as “spooky action at a distance”. Please note though that in NO experiment has anyone seen a violation of the speed of light due to entangled systems. While correlation does in a sense travel with infinite speed (it is istantaneous), it does not transmit any information (no signaling is possible), thus not violating relativity in any way. We worked on this back in 2007, with entangled photon transmissions over 144km in free air at the Canary Islands.
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As for parallel universes, some theorists (notably David Deutsch) have coined the term multi-verse and gone running off madly with it in order to develop an idea which explains the aforementioned unresolved experimental results. There is NO evidence whatsoever to support the idea, and no way to test the validity of the idea with present technology. The true death of the idea ought to plainly reside in the sheer number of “multi-verses” required to accommodate the idea. It’s simply far too ugly and messy to be remotely true. Of all the things Albert got right, I’m always struck by this one: “I always know when I have found the correct solution because it’s so elegantly beautiful.”
The multi-verse is not elegant. Personally, I see no need for N-to-the-Nth-power universes when we have such an amazing, seemingly infinite and little understood one already.[/quote]
I do agree, even though my problem is not with the inelegance of the theory, rather with the fact that is probably will remain untestable and unfalsifiable. Also, it does not further our understanding for it does not provide predictive or explanatory power greater than Quantum Mechanics without the “many worlds”.
Those of you curious about the subject should know last October Taipei hosted one of the biggest, high level events on Quantum Mechanics and Quantum Information http://www.quantumhorizons.org. We are close to publish the Proceedings of that meeting. Videos exists of all of our sessions, though I am not sure we will be able to freely distribute them. 