Quantum teleportation is even weirder than you think



Quantum teleportation is even weirder than you think

A write-up of the work in Discover reports that the scientists “have successfully transmitted quantum entangled particles” — only to clarify, confusingly, that “unlike science fiction teleportation devices, nothing physical is being transported”.

But wait: didn’t someone once say information is physical? That was physicist Rolf Landauer3, a pioneer of information theory. So if you send nothing physical, how can you transmit anything at all from A to B?

This is one of the deep issues that quantum physicists and philosophers still argue about. We can debate whether ‘quantum teleportation’ as a term is a catchy way of conveying a scientific idea, or a misleading bit of hype. But the real question — what, exactly, is transmitted during quantum teleportation, and how — touches on issues much more profound.


Lost Pilgrim
Is it possible to untangle particles by, for example, having one observer affect the spin of one while another observer affects the spin of the other a different way?
Technically, you "untangle" the particles when you measure the properties of one of them, entanglement itself being a state of uncertainty. Of course this is not as straightforward as it seems, and the fact that entanglement can do odd things like reaching into the past, adds another layer to the whole "observer problem".
My understanding is once the measurement is made on one, it forces the other one into the opposite spin. The act of measuring destroys the entanglement. E. Flowers reference to reaching into the past I think refers to Seth Llyod's work in quantum illumination. Lloyd found entanglements which are completely destroyed in fact leave a trace that can be both detected and recorded.

Untangling pairs is in fact too easy. Keeping the pairs entangled is very difficult. In order to make quantum computing a reality they need to figure out how to stabilize the pairs. So Lloyds work is an important step in that direction. The Russians a few years ago said they had actually restored untangled pairs. Now with the Chinese sending entangled pairs through space, science is making incredible strides in moving quantum computation beyond theory into actual systems.