View Single Post
  #54 (permalink)  
Old 16th September, 2005, 11:11 PM
cadaveca cadaveca is offline
Member/Contributor/Resident Crystal Ball
Join Date: March 2004
Posts: 7,451

Originally Posted by Áedán
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.
Entanglement, my dear Aedan, entanglement. You are not firguring in entanglement.
Reply With Quote