Tuesday, June 20, 2017

Quantum Entanglement

One of those things that works, but shouldn't.  6/17/17 Chicago Tribune discusses the latest experiments where two photons hundreds of miles apart mirror each other's state.  Clearly impossible, but proven to happen.  The potential for instantaneous communication across the enormous distances of space should be obvious.  The Star Trek transporter is really just transmitting information about an object, not actual matter, so quantum entanglement might allow long distance transmission of data without the struggles about range and power.  How you get that information in enough detail to replicate a human is a different nearly impossible task.


hga said...

The potential for instantaneous communication across the enormous distances of space should be obvious.

Except that's something that Special Relativity explicitly forbids, and the last time I checked on quantum entanglement (many years ago) it wasn't claimed it could violate it. Still seems to be the case; you very much can't trust Wikipedia on topics like this, but for what it's worth, here's their page on the no-communication theorem.

Which is not to say something very interesting isn't going on, something Einstein himself described as "spooky action at a distance" (which he considered to be impossible, but he was long dead before experimental evidence was obtained).

StormCchaser said...

I agree with hga. Quantum Entanglement doesn't let you violate special relativity. As Einstein showed, if you violate Special Relativity, you can travel backwards in time, which violate the laws of cause and effect that all of science (and logic) is based on.

Alex said...

The previous commenters are correct. Entanglement doesn't give you FTL communication. Here's an illustration:

Begin with the classic Schrödinger's cat thought experiment, except that we have two boxes each with a cat inside, and we trigger each box with one half of a pair of entangled particles such that the result of the death/survival of each cat will be opposite as in the other box. I pick up one (still-closed) box, you pick up the other, and we fly away in spaceships until we're a light-hour apart from each other.

I open my box and observe that my cat is alive. I therefore know, instantaneously, that your cat is dead, but that doesn't allow me to instantaneously send you any message at all. I can send you a radio message saying, "Ha, ha! Your cat is dead!" but it won't reach you for and hour.

In short, entanglement is not a back door to faster than light communication.