Question

For a course titled Quantum Mysteries for everyone;

Why, on final account, one cannot use Quantum Mechanics to signal faster than light? Explain.

Answer 1

By the property of Quantum entanglement, two particles can be entangled such that if we know the state of one of the particles we automatically know the state of the other. Thus if these particles are seperated over a huge distance by finding out the state of one of the particles, the state of the other particle at that huge distance can be found out immediately faster than the speed of light. But this property cannot be used to transmitt information faster than the speed of light. But there is one problem, entanglement only works if the state of the particle is found out. If the particle is forced into a particular state, the entanglement is broken. Yes by measuring the state of the particle the state of other particle be found out, but as this state is a random state the other particle has the opposite of this random state, but there is no way to transfer any unique information through the random state. Transferring information requires us to force the particle to a certain state to send information according to pre defined norms.
Thus quantum entanglement can be used to gain information faster than the speed of light, but not create and send information.