maybe you have already heard it.
“spukhafte Fernwirkung” or “spooky action at a distance” – Albert Einstein
what is it? Are we able to transmit information faster than light using it?
Spooky action at a distance or also quantum entanglement. This is very famous phenomenon which seems to allow information to travel faster than light, luckily not, otherwise we would have to throw all our physical theories to trash (or maybe it would benefit, who knows).
Particles have spin as I have shown countless times in posts about standard model or about particles and so on. They have also other properties which has to do with quantum entanglement.
What experiments shown was that when independently measure two photons for example the results about their attributes are correlated. This is indeed spooky because it does not matter how far away those particles are but always the result will somewhat be similar.
The picture above from NASA page well explains how this works. The people there are detectors called superconducting nanowire single photon detectors which are cooled to be superconductive and when photon hits the wire it changes the resistance in the wire to some higher value so you can record the event.
Why does not this break the rules of speed of light? Because there is actually no data transmitted. You can not use it to communicate since the results are random anyway. And when you know your result you also know the result anywhere in the Universe, that does not matter because it was random.
I will just repeat: you need pair of entangled particles, for example laser beam can create photons that when they go through crystal and they split, they become entangled, measuring one particle will influence the other.
Einstein thought that this is because the particles contain what is called “hidden information”. That when they are created at one point in the crystal from the laser beam for example, that they make their “secret plans” on how their spin will work out when they are measured, which would not need any faster than light travel. In this video, Derek Müller shows the experiment of Bell that shows that there is no “hidden information” and how the measurements work, because what you can do is to measure the spin of particle in various angles which changes the probability of the particle to have that kind of spin.