Spooky Action at a Distance

The great Albert Einstein never fully accepted Quantum Mechanics, quoted as saying, "God does not play dice with the universe."

One of his biggest issues with the theory is quantum entanglement. I spoke briefly about it in the previous post, but essentially it boils down to this. Quantum particles that are in an "entangled" state instantaneously "know" information about the other particles in the state.

Lemme give you an example. One of the simplest (in a way...) quantities an electron can have is called spin. This spin can be one of two things - up or down (The details of this are not important...) Now, say I put to electrons into an entangled state so that if I measure one of them as up, the other is down, and vice versa. Well, the laws of quantum mechanics say that this happens extremely fast, perhaps instantaneously! Imagine this - I take one of these entangled electrons in a space ship and bring it 5 light years away (that's the distance light goes in 5 years! A long way!) and leave the other on earth. Quantum mechanics predict that if I measure one electron as up, then if someone way back on earth makes a measurement at the exact same time as I do on my space ship, he'll measure the other electron as down.

What does this mean? The particles somehow communicated, over a distance of 5 light years instantaneously. Relativity predicts that no information can travel faster than the speed of light, yet quantum particles can still somehow communicate with each other of massive distances at many many times the speed of light. This effect has been verified to at least 10,000 times the speed of light! Entanglement is a very active research topic because of its huge potential for new technology, and I'm going to post a more about it's applications in my next several posts.