will quantum computers ever be built?

Question

As I understand it a quantum computer is a machine built under the foundations of Quantum Mechanics that would make the circuits so small that they can be in more than one place at a time (the miracle of minaturization is reaching it's limits on how small a transistor can get).

Answer 1

That's not quite what a quantum computer is. Have a look at the wikipedia article. The implications scare the bejeez out of me.

Answer 2

Nope. Quantum objects can not be in more than one place at a time. They can be in more than one STATE at a time. But physical coordinates in QM are not states. So what you have heard or what you think you heard is incorrect.

And yes, quantum computers are being built. And no, they will not replace ordinary computers and they will not be infinitely fast.

If you ask me, quantum computing is nothing but a fashion and a fad. It will hit its limits soon and then all research will seize and go on with something else. Why? Because nature has an unwritten law called "There is no free lunch!" and quantum computers, on paper, seem to violate that law.

IMHO there is a very intricate limit to quantum computing which has to do with environmental noise and decoherence. And this will limit the usefulness of the quantum computer in very much the same way as it has stopped the real world analog computer from being useful.

If you remember, an analog computer can theoretically represent real numbers (as in elements of the mathematical set R). Addition of two real numbers as well as subtraction, multiplication and division are worth an infinite number of digital operations because the binary representation of any real is infinitely long.

So why can't an analog computer not replace and infinitely large digital computer? Because there is a little thing called thermal noise (a present of the second law of thermodynamics) and it reduces the precision of any voltage/current in an analog computer to about five to six decimal places. Half as much as your pocket calculator does!

Now... the quantum computing people operate under the assumption that they can somehow beat noise and the second law. And if you simplify a lot of the theoretical calculations of how a quantum computer works, they really can. But I bet that if you do not simplify, the noise will always come back and hit you, no matter how smart you are!

And in ten or twenty years from now we will call the quantum computing people "the last platoon of science warriors trying to beat the conservation law of lunches"!

:-)

Answer 3

emucompboy is right, quantum computing is much more interesting than merely a "miracle of minaturization". Researchers already have rudimentary "quantum computer" circuits, and proposals have been advanced for ramping up to practical working quantum computers. The abilities of such computers will be truly mind-boggling, seemingly bordering on fantasy. It will be the next great revolution in computing technology.

Addendum: Check out the reports coming in about developments in quantum computing technology. So, it doesn't have any better future potential than analog computers? Funding for quantum computing technology is already approaching a billion dollars. Even IBM is pouring money into it. See link.