Scientists have managed to separate a pair of entangled particles by a distance of 1,200km, more than 10 times longer than the previous record.
Physics behaves differently at very small scales from how it does at scales we’re used to. We call the laws that describe this behaviour quantum mechanics.
One thing you need to know about quantum mechanics is that instead of behaving in a normal, sensible way, matter behaves like a particle and like a wave.
The other thing you need to know about quantum mechanics is that you should say goodbye to certainty. Because a particle is acting like a wave, we can’t know for sure where it is...
...until we measure it. Once we’ve done that, if we know its location, we can’t know its speed. And if we measure its speed, we can’t know its location.
In 1935 three physicists – Einstein (yes, that one), Podolsky, and Rosen – were trying to poke holes in quantum mechanics when they first described an example of quantum entanglement.
But the term “entanglement” was actually coined by Schrödinger (of putting-cats-in-boxes fame) later that year.
He called it “the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought”.
Einstein wasn’t very happy about entanglement and described it as “spooky action at a distance”.
The basic idea is this: If two particles come into close contact with each other, they can become linked.
The fates of these two particles are now intertwined, and we call them entangled.
We can move these two entangled particles very far away from each other and they stay linked.
Because they behave in a weird, quantum way, we don’t know what the properties of the particles are until we look at them.
But once we look at one of the particles, we’ll also know what state the other one is in.
This is true even if the second particle is on the other side of the universe.
This is a huge deal, because it means we’re sort of communicating at faster than the speed of light.
Practically, of course, it’s a bit more complicated than that. (Isn’t it always?)
We can’t just entangle two particles then slingshot one of them to the far reaches of the universe.
There are two ways to transmit entangled photons: through optical fibres or through open space.
But as the length of the optical fibre or amount of atmosphere increases, so does the likelihood of losing the photon along the way.
But by creating the entangled particles in space and sending them down to Earth, scientists have been able to bypass a lot of that interference.
Being able to entangle photons over long distances is crucial if we want to use entanglement for things like secure communication, quantum computers, or even quantum teleportation in the future.
But if you’re still struggling to make sense of this, just remember what Richard Feynman once said: “I think I can safely say that nobody understands quantum mechanics.”