Friday, July 16, 2010

quantum entanglement and information transfer

I have been reading about the EPR paradox (Einstein, Podolsky and Rosen) and the implications of quantum entanglement. You can think of entanglement like the drawing of one of two cards. The two cards are entangled in the sense that if I draw a red card while we know the other is blue. Then by checking the card I have drawn, you will know exactly what card is left, the blue card. This concept is the same when talking about two objects in entangled quantum states. If I am on the moon with a particle which may be in state 1 or 2, and you are on the earth with a different particle in state 3 or 4, but our pair of particles may only be in an exclusive combo state of either 1 and 3 or 2 and 4, then if you measure the state of your particle, I need only to ask you what your result is to determine the state of mine. HOWEVER, information can only travel at most the speed of light. SO, if we measure our particles simultaneously, then we should be able to have the possibility of obtaining a result which does not match either of the two possible states I listed before (1 and 3 or 2 and 4), since information of your particle and my particle will not be able to reach the other in time to "let the other particle know" that something has changed or that a measurement has occurred. I am not convinced that entanglement can exist at such distances. Furthermore, how does the effect of measurement influence entanglement (by measuring particles or systems, we effectively put our system into a certain state...from which it may then evolve according to the state we measure it in).

No comments: