Quantum question

[ironphoenix]

Read this article on quantum entanglement first.

If your brain hasn't imploded yet, here's a question:

What would happen if Alice and Bob checked the correlations of their measurements before Victor decided whether or not to turn on his entangler?

(Link ganked from dagibbs!)

Comments

[dagibbs.livejournal.com]

I don't think it would matter.

Alice & Bob's reading of their measurements is already being affected by Victor's decision made 14 nanoseconds after they took their readings. (Or, perhaps, what A&B read is affecting Victor's decision.)

And, while 14 nanoseconds sounds like a really short amount of time in the human sphere, it is actually a long time in the quantum sphere, or heck, the computer sphere -- a 4 GHz processor would execute 56 instructions in that time.

[ironphoenix.livejournal.com]

This would allow Victor to send a message backwards in time to Alice and Bob (i.e., useful reverse-time causation), which is why I think it's not necessarily clear-cut. Thus far, reality has been pretty good at preventing that kind of thing.

[beable]

I think my real problem is that I'm waiting for Eve to intercept the proton stream), because, as a Ghostbuster, she loved Bob first.

[dagibbs.livejournal.com]

P.S. you linking appears to be broken?

[dagibbs.livejournal.com]

Yes, it would seem that it might.

From the arstechnica article, "That little bit of cabling was enough to ensure that anything that happened at Victor occurred after Alice and Bob had done their measurements."

And:

"The picture certainly looks like future events influence the past, a view any right-minded physicist would reject."

They do say, though:

"As always with entanglement, it's important to note that no information is passing between Alice, Bob, and Victor: the settings on the detectors and the BiSA are set independently, and there's no way to communicate faster than the speed of light."

So, something about the way entanglement works at the quantum level does preclude information transmission... or, at least, we think so.

All in all, it is some pretty crazy science.

[ironphoenix.livejournal.com]

Thanks; fixt!

[ironphoenix.livejournal.com]

I figured you might get stuck at Eve, yes.