Entangelment thought experiment

[Aranfan]

This thought experiment is a variation on that poor cat in a box who belongs to a physicist whose name I can't spell. Instead of the cat living or dying is determined by the measurement of an entangled particle at a predetermined time. Now, a physicist ten light minutes away has the other particle of the pair. The Machine makes the measurement at the predetermined time and the cat either lives or dies, it immediately sends a lightspeed message to the physicist. Knowing the time the Machine would take the measurement, the physicist finishes measuring her particle 9 minutes before the Machine's lightspeed message is due to reach her.


Does the Physicist have FTL knowledge of the cat's fate, or did I mess up somewhere?

[Samuel]

Schrödinger's Cat.

[Grandmaster Jogurt]

This is pretty much exactly the Einstein-Podolsky-Rosen paradox. And the answer is that you don't get FTL knowledge of the cat. I'm afraid I cannot actually go into the details, though, because my QM book is in Arizona and I don't even remember the concept of the derivation, let alone the mathematics.

As a side note, I came up with a similar device used as an FTL telegraph after the lecture about waveform collapse. I wonder how many people think this sort of thing up when they're introduced to QM?

[Sarevok]

Everytime Han Solo jumps to hyperspace the universe kills a kitten somewhere.

[Fingolfin_Noldor]

Someone wrote a paper on this... I forgot if it was John Preskill, Jeff Kimble, Luming Duan, or was it Peter Zoller/Cirac.

Let me see if I can dig up anything when I'm free.

[Aranfan]

Why not? I can't figure out why you wouldn't get FTL knowledge from the OP's set up. Apparently my classical intuition is wrong, but I would at least like to know why it's wrong.

[Feil]

FTL transfer of information violates relativity because if we allow it for multiple inertial reference frames you can transmit information backwards in time (the laws of physics are the same in all inertial reference frames). Or, as somebody smarter than me one said, "Relativity, Causality, FTL: Pick Two." http://www.theculture.org/rich/sharpblu ... 00089.html