starship-design: Ideas for the future

[Steve VanDevender <stevev@efn.org>]

Kyle B writes:
 > 1. A superluminal communication system. An experiment was done a couple of 
 > years ago proving that two photons that had been entangled would change 
 > states simultaniously even if they were seperated. This has been shown to 
 > happen at exactly the same time, i.e. faster than light. imagine if one 
 > photon was placed aboard a spaceship and the other left on earth. it would 
 > be a simple matter to detect the polarization of these photons, 
 > unfortunately not without breaking the entanglement (yet). If the 
 > polarization could be changed fast enough, it could possibly be used to 
 > transmit digital signals in realtime- even between places light years apart.

Quantum mechanics gives, and quantum mechanics also takes away.  The
same laws of quantum mechanics that allow for quantum entanglement also
say that entanglement can't be used to communicate information.  The
entangled particles may change state "simultaneously" when one is
observed, but you don't know what state they were in before that, so you
can't communicate anything by observing one of them.