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A lot of the ado about quantum computing is really very funny. In the 70's we had a version of the quantum computer called and optical computer programmed using holograms. These amazing devices could do complex problems like pattern recognition instantaneously.

One cool example was a hologram of the word God which when illuminated by a laser through the rear into a page of the Bible would make a bright spot everywhere the word God appeared on the page, instantly==== ====

The new quantum computers are not that different, the same quantum processes are involved, but they may eventually prove to be more practical. They are still in the "toy" stage and are likely to have only token application for many years.

First of all, we are now solving problems proven intractable by other means, notably digitally simulated neural networks and evolutionary programming. Quantum computers will not replace these techniques for quite a while and the improvements will be marginal if any for a much longer while. There will not be a revolution in computing due to quantum computing.

There are two aspects of quantum computing that are quite interesting. One is they use QBIT logic, where the state of things in the present is indeterminate until the state value is used in the future.

This delayed value reasoning actually gives different answers than classical logic for the same problems and the answers seem apply better to the real world because the include a time dimension absent in classical logic. See QuantumLogic

The second aspect is that the future values are all computed in parallel yielding potentially high speed, near instantaneous results depending on the problem setup.

But the problems will be finite and the solutions will be finite. In the quantum, nature herself has a finite nature, But with a large number of QBITS it will seem practically infinite.

"I believe that such a computer could be capable of producing a virtual reality with (near) infinite possibilities for an (near) infinite number of individuals linked to it." - the Matrix :)

Absolutely==== ====

I know this from first hand knowledge, I call it the physical world. The universe is after all nothing but a quantum computer with a gazillion QBITS.

Quantum computers, like the old analog and optical computers, for most applications will be simulated on ordinary sequential machines even when our computing elements are themselves quantum elements. Setting up problems for quantum computers is like trying to build an ocean liner out of Lego bricks. Testing real systems or digital simulations will be much easier than making a quantum models for the foreseeable future.

The nature of quantum communication is that it is discrete and private among the participants. There are no definite states manifest between communication events because nothing happens to manifest them. State change events are propagated by events either 100% or not at all. It is not possible to probe the state of a qbit as it assumes a definite value when probed.

The mystique of the qbit is overrated. No superposition of states or quantum entangelment is ever manifest. It is equivalent to think of them as being in a state that is not manifest until an event occurs and the state change is manifest in some participant in the future. The set of future potential participants will determine the outcome later.

No probability has ever been measured. Events happen or they don't, probabilities are emergent, not fundamental.

You are in good company if you take QM literally and think reality really computes all the probabilities of everything before making a decision as to what happens or that everything that might happens actually happens in some other world. Many great scientists including Penrose and even Wheeler may agree with you. But I don't believe there is any magic in the quantum. I don't believe the laws of physics are any different in quantum systems. The probabilistic behavior of quantum systems is readily explained by irreducible incomplete knowledge. There is no call to invoke special quantum powers. For example, Hoofts article http://arxiv.org/abs/quant-ph/0212095 confirms many prior results that show a deterministic underlying system is consistent with QM explained by loss of information locally. Nobody ever witnessed a qbit and nobody ever will, what is manifest is discriminated in ordinary bits by actual participants. There is no reason to think that eigenvalues that are not discerned by any actual participant exist anywhere but in our minds.

It is true that there is tremendous parallelism in quantum interactions and there is no simpler mathematical model then the quantum system itself. But, QM itself dictates that events happen discretely, 100%, or they dont. The probability of a measurable being manifest without a participant disposed to witness, bu QM itself, is zero. We are limited in how we can know the possibilities, but the quantum is free manifest itself deterministically. If we knew what measurement future participants would make and how they will propagate them we would not need to keep trace of all those possibilities. We must consider all that might happen, but nature herself only need only manifest what actually happens. Schrodindgers cat is either dead or alive, only our knowlege changes when we look and manifest it as alive or dead by making such a discrimination part of our world.

Despite the fact that the quantum need not be nearly so complex as our limited view of it must be, it still suggests our universe is a information processor with formidable power in an information ecology manifesting order on every scale. From simple systems great complexity emerges.

Quantum theory does not distinguish between what happen and what might happen. As scientists we ought to. If you put aside orthodox QM for a moment and reconsider the arguments, the distintion is clear. What exists is manifest by participants, nothing else exists. Probabilities are not anything real. The probability of rain does not cause rain, a cloud overhead with water falling out of it does.


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