One of the strangest consequences of quantum mechanics is entanglement, where two particles can be connected in such a way that an observation of one immediately collapses the wave function of the other, no matter the distance. This seems to break the laws of physics, allowing for instantaneous communication. Could it be possible to use quantum entanglement to communicate faster than the speed of light?
Yes to them changing faster than light. But the state change can’t be used for information.
This is because when you read the spin that measurement causes in the other particle a definite state.
But you can’t predict the state or use it to convey some information. All you can do is make it happen and then later confirm the other party read the same (which has to occur at slower than FTL speeds)
Quantum Entanglement and the Great Bohr-Einstein Debate | Space Time | PBS Digital Studios
E.g. causality is always preserved and so relatively isn’t “broken”
Unless we discover a way to force a specific, and reproducible change. If we can force just one specific state we can effectively utilize binary communication across the entangled pair. One representing that state and zero being any other state.
Unfortunately it won’t work. By its nature when you make the change you collapse the wave function.
You can do it in such a way it’s confirmed that you did so. But only after verifying with the original two parties that it happened. Again, only within the confines of relativity.
Another good video that may explain the speed of light and causality it a little better here
The Speed of Light is NOT About Light
A lot of great videos by that channel covering particle physics, relativity, etc. I highly recommend it.