Quantum entanglement is mind blowing. Einstein, who was troubled by quantum physics’ implications, called it “Spooky action at a distance”.
Sometimes, particles are not independent from each other, the quantum state belongs to the whole system. Those particles might stay correlated even if they are at opposite ends of the universe.
Let’s say our system is a pair of particles. Those particles are quantum airships which can be English or French airships, but the whole system should be in English and French.
If one observer looks at airship A, airship B’s state will then be fixed instantaneously. For instance, if airship A is observed as French, airship B will automatically be English. But if airship A is observed as English, then airship B will be French… Some try to explain it with hidden variables: in this case, it’s obvious airship B is English if airship A is French, because observers know the initial state is both English and French. However this airship example is an over-simplification. Experiments like the one made by Alain Aspect tend to say there are no hidden variables in quantum entanglement… Spooky!
In real life experiments, an observer would not be able to tell B’s state for sure, without A’s observer telling them the result – and this information can’t travel faster than light according to the theory of relativity.
It is so spooky it has inspired a lot of plot devices, which are not always scientifically accurate, as quantum entanglement is often used as a way to teleport information – that said, with extra worm holes, the plot’s physics gets blurry…
In the Amber Spyglass (2000), the last book of His Dark Materials by Philip Pullman, Lady Salmakia, Chevalier Tialys and Lord Roke, the dragonfly riders, communicate across space and universes through quantum entangled resonator devices.
In SciFi TV series Fringe (2008-2013), similar devices, this time quantum entangled typewriters, are used to communicate instantly across different universes:
… to consciousness
Quantum entanglement is also sometimes used as a mean to link consciousnesses across the multiverse.
The two vampire lovers in Jim Jarmusch’s movie Only Lovers Left Alive (my favorite 2014 movie so far) talk about quantum entanglement, they seem to be a metaphorical embodiement of entangled creatures.
In 2013 video game Bioshock Infinite, the Lutece twins are counterparts from alternate universes, and they can communicate thanks to quantum entanglement.
In Empress of the Sun (2013), the third Everness book by Ian McDonald, one of the parallel Earthes only bear twin humans, each person being born with a quantum linked twin. This link still works in parallel universes, making those “twins” ideal multiverse spies…
Quantum theory applications such as quantum computers are a reality, thus quantum entanglement seems a realistic enough plot device, leading people to ask themselves, what if?