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Old 13th September, 2005, 09:19 AM
Aedan Aedan is offline
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Join Date: September 2001
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Quote:
Originally Posted by cadaveca
i simply said it could signify 2x2500 power bits, not those many states. those 4 states, as well as multiple paths , allow for the higher POSSIBLE info tranmitted.
Qubits are pretty much fixed in a location, as coming in contact with other matter destroys state, and the data is encoded in the state of particle. Moving that particle from A to B causes all sorts of issues, as does attempting to directly measure anything about that particle.

Transmitting information requires states. If you only have four states, then you can only transmit two bits of information in that channel. Superposition doesn't allow you to transmit more information, as the particles have the same characteristics. Sure, your particle will travel multiple paths (if they're identical), but will only be carrying the same information, so is part of the same channel. It doesn't allow you to transmit more information. Hence, you're still stuck with the same four states, no matter how many paths the photon takes, as it's the same photon on all paths. (See Shannon for more about information theory)

Photons are limited in the amount of information they can carry due to the fact that they travel at the speed of light. Other particles are not limited to two spin states, as they travel more slowly. Interaction with any other matter will also lead to decoherence and the loss of any information encoded.

Sure, the memory uses interaction between quantum optical and magnetic effects in order to effect storage and retreival, but that's not quantum computing.

Thus, so far we have determined that a) they're not using quantum computing, no matter how hard they claim to be; and b) they're using a mixture of magnetic and quantum optical in order to store data in some form of crystal lattice. My understanding of this is that it allows the effect of a magnetic domain (IE, little bit of iron) to affect the optical properties of the material. So, instead of reading the data back using a magnetic head, a la hard disk, they read back the state optically using a laser.
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