Quantum Computers

[clover leaf]

I've heard a lot of fuss about computers that use particles in place of electric charges (quantum computers) thus increasing speed. Think about it, school computers that aren't as slower than my grand mother. But is it possible? And if so how would they work?

[Bazzy]

I don't think it's really possible since small particles don't have a fixed state at a fixed time so you'd end up having a computer where all bits are at the same time 1 and 0.

[chrisname]

@Bazzy,
Would that be like a kind of Schrödinger's computer?

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if (x) std::cout << "x is true\n"; if (!x) std::cout << "x is false\n";

x is true x is false

[Bazzy]

It would be like

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if ( x & 1 ) // testing a single bit std::cout << "cat is happy\n"; else std::cout << "cat is not quite happy\n";

may output "cat is happy" or "cat is not quite happy"

It would be really good for RNG but really bad for anything else

[chrisname]

That would be... interesting. So the code
std::cout << (x & 1) << std::endl;
would output a different result at different times?

[Bazzy]

No, it would output different result at the same time ( if you assume the existence of level 3 parallel universes )

[helios]

Quantum computers already exist, albeit at very small scale. Just a couple qubits of state, but already Turing machines, although I don't know whether they're deterministic or not.

[Bazzy]

The last time I've heard about them, they were purely hypothetical

[firedraco]

AFAIK, they seem to basically let you operate on "sets" of bits as if they were all combinations at once...something like:

print(some_8_bit_set); looks like one call, but would give you:

00000000
00000001
...
11111111

At least that was how I interpreted it.

[thepedestrian]

I think its very hard to maintain a particle stream that is stable. For example, lets say that in the construction of this quantum computer, we pass charge through an electrical beam. We have to account for many factors including ionizing, reactivity, and even something as simple as preventing light for entering. Although I believe this is very much possible, there is high possibility that some element will always be unstable and therefore if for whatever reason a electron happens to fire of, then we might get different results.

This is a good question and I'm not much of a chemist to talk about this subject but interesting indeed.

[PiMaster]

Like Helios said, they already exist, but the largest is like 24 qubits (quantum bits), if I'm remembering correctly.

For things like this, Google and Wikipedia are your friends:
http://en.wikipedia.org/wiki/Quantum_computer
http://www.howstuffworks.com/quantum-computer.htm