Slow Monday science thread - quantum entanglement

With the thread about Google's quantum computer the other day, I thought it would be interesting to look more at the science.

A, if not the, cornerstone of quantum mechanics is what's known as "quantum entanglement." This is basically says that with 2 quantum particles if you measure or detect one, it's "partner" will have a known characteristic.

The prevailing theory at this time is that the quantum particle basically exists in every possible state, until it is observed or measured. At this time, it assumes a given state. At the instant the one particle assumes its state, its partner particle assumes a correlating state.

This theory has been tested and verified multiple times. In July of this year the first picture of this phenomenon was taken.



What they did in this experiment was split a stream of photons. One of the paired photons was directed straight at a detector. The other photon was split off and sent through a series of phase changes. What they observed, and what the picture shows, is the first proton shot straight at the detector underwent the same phase changes as its "entangled partner."

This is one concept that Albert Einstein missed on. He didn't believe there was anyway for 2 particles to communicate across a distance as superluminal speeds to influence each other. He called it "spooky action at a distance."

Discuss.