how is quantum entanglement faster than light communication ?

Question

How does that affect relative physics?

Answer 1

Short answer: no one really knows. Quantum entanglement involves the propagation of spin or other characteristics (called states) of pairs of particles that are "entangled" at, as far as we can tell, much faster than light, and potentially instantaneously. Theoretically, if this effect is actually real, one could use entangled pairs of particles across vast distances to send instantaneous messages by altering the characterisitics of one of the particles - which would violate the whole no information can travel faster than c. Unfortunately, no useful information can be transmitted at faster than c - preserving classical concepts of causality - this is part of what is called "the No Communication Theorem" which is shows that the receiver of a message using quantum entanglement would not be able to tell the difference between an actual message and random "noise."

Another somewhat related effect is that of quantum "tunneling" where particle information is passed through a barrier at what appears to be much faster than c. But again this effect does not allow for actual useful information to be transmitted faster than c.

Answer 2

In actual fact, this is a well known concept known as the EPR paradox after the people who first proposed it as a thought experiment (Einstein, Podolsky, and Rosen). It is commonly used in physics courses as a bit of a test of the students. Here we have two of the most fundamental theories of our time, relativity and quantum mechanics, apparently disagreeing.

Heres a briefish explanation but you can check it out on wiki....

Imagine we have an "event" that produces a pair of entangled electrons. Electrons have a property called spin that can be "up" or "down". When the pair is produced they are entangled because if one is up then the other HAS to be down but we don't know which is which yet. Now imagine that the electrons fire off in different directions towards two detectors placed a significant distance apart with one (lets call it A) slightly closer to the initial event. When the first electron hits A we can find what spin it has and hence we know instantaneously what the spin of the other electron is even though the second electron is a significant distance away. So the information of the spin state of the second electron has travelled instantaneoulsy and we have violated relativity, right? WRONG!!!! Relativity puts a limit on how fast information can travel whereas at the heart of quantum mechanics is probabilities. We don't know what the spin state of the first electron is going to be until we detect it at A. As the spin state is randomly chosen (its called the collapse of the wave function) we can not know to 100% accuracy what the spin state is going to be before we detect it. This means the spin states are completely random. As they are completely random theres no way of sending a meaningful signal because we have no way of controlling what the spin state of the electron at A is going to be. Thus relativity is NOT violated because we can not use this technique to transmit a meaningful signal.

Answer 3

Give Joe the points. He's a dude. Bob is not a dude. Me, I have absolutely no flepping idea...

Answer 4

?