Can we make use of quantum entanglement to find out what actually happens inside a black hole?

13 December 2016

Question

Can we make use of quantum entanglement to find out what actually happens inside a black hole?
-Sreejith

Answer

Andrew Pontzen had the answer to Sreejith's question...

Andrew - Quantum entanglement is one of the most beautiful and bizarre phenomena in all of physics quite frankly. It comes from this world of quantum physics that we've been discussing quite a lot already on the programme, the physics of the very small. And it's this phenomenon where, seemingly, what you do to one tiny little chunk of matter, one tiny particle, in one place can instantaneously change how another particle in a completely different place is behaving. And when I say instantaneously, bizarrely, I actually mean instantaneously.

We have a kind of idea in physics that nothing can go faster than the speed of light, but there's no way that one part of the universe could influence another part of the universe without there having been time for some light at least to get from point A to point B. This seems to break that idea.

So it's actually a very sensible question to say - okay, sure, if I drop something into a black hole I'll never see it again, at least not in the form that I dropped it in. But could I use this bizarre effect of quantum entanglement to find out something about what's happened to it?

Chris - Is this what they dubbed "spooky action at a distance?"

Andrew - Yeah. It's not just they, it's Einstein that dubbed it "spooky action at a distance," because he hated it. It's so weird, it's so cutting against the grain of everything else we know about in physics.

Chris - But Niels Bohr said "if you're not baffled by quantum you didn't understand it."

Andrew - Absolutely. And I think that's a very fair way of putting it. However, what we do know about this phenomenon of quantum entanglement is you cannot actually use it to transmit information faster than the speed of light, which seems to contradict what I just said. So although one chunk of stuff can influence another chunk of stuff at a great distance seemingly fast than the speed of light, that can't be used to transmit a message.

So suppose I gave you one half of my entangled pair of particles and you tried to use it to transmit me a message.

Chris - You shared your quantum entangled mascara with me?

Andrew - Absolutely. I would only share it with you Chris.

Chris - I'm touched.

Andrew - Suppose we did that. Suppose you tried to figure out how can I send Andrew a message. Unfortunately, it turns out that there's actually a mathematical theorem showing you cannot use this effect to send me a message. If you can send me a beam of light at the same time, then you can kind of boost the amount of information that gets sent. But because the way that one of the pair affects the other is extremely subtle, it can't straightforwardly be used to send a message as you would with say a beam of light.

So if you can't put things in contact with a beam of light, you also can't put them in contact with quantum entanglement. So the answer is no.


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