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Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

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Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#51

Post by scotty79 »

krcz wrote: post #30
pep-ok wrote: post #26

Earlier quoted context omitted.

yes, i think, if you mean 2 and 3. you have 1-2 and 3-4, then you entangle 1-4 which I think should lead to 2-3 entanglement without the 2-3 couple ever interacting at all. I think it is called entanglement teleportation.

Yeah, I've meant entangling 2 & 3 pair and measuring 1 & 4. But my concern is if we can still use this trick after measuring 1 & 4?

This can't possibly work because it would mean that you cou ld measure 1&4 and get result that proves that they were not entangled and then entangle 2&3.

Of course it's possible that 2&3 entanglement trick doesn't always work and it never works if preceeding 1&4 measurment proved that they were unentangled. But this is some serious cheating. :)

Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#52

Post by [deleted] »

krcz wrote: post #30
pep-ok wrote: post #26

Earlier quoted context omitted.

yes, i think, if you mean 2 and 3. you have 1-2 and 3-4, then you entangle 1-4 which I think should lead to 2-3 entanglement without the 2-3 couple ever interacting at all. I think it is called entanglement teleportation.

Yeah, I've meant entangling 2 & 3 pair and measuring 1 & 4. But my concern is if we can still use this trick after measuring 1 & 4?

[deleted]

Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#53

Post by scotty79 »

andrewflnr wrote: post #40
tedsanders wrote: post #32

Earlier quoted context omitted.

There are certainly interpretations of QM that are deterministic. See many worlds, for example.

Personally, I've never found that a comforting alternative.

It just because people tell about it as if all the possible divergent trajectories through phase space happen not just ours. What they actually mean is that the possibilities are vast and we have no idea why reality chose exactly this path because it's not in any way priviledged.

It's like a ball a top of the totally symmetric hill. If you consider phase space it contains ball rolling down in all the possible directions but noone claims that ball rolls in all of them in alternate universes. It rolls down in exactly one way though we might never have any idea why it chose this one.

Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#54

Post by lmm »

Retric wrote: post #46
lmm wrote: post #34

Earlier quoted context omitted.

The standard answer is the Bell inequalities, but if you only care about deterministic vs. nondeterministic then Conway's "free will theorem" is a bit simpler. (The result is that either which quantities we choose to measure must be deterministic, or physics must be nonlocal (i.e. what we do in one place can change what we measure in another place even if the two experiments happen simultaneously), or the results of…

Nothing says we live in a local universe.

There's no proof, sure. But nonlocality is very counterintuitive, arguably more so than nondeterminism (and there are no familiar classical/macroscopic phenomena that exhibit nonlocality, whereas many familiar things at least appear nondeterministic in practice).

Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#55

Post by krcz »

pep-ok wrote: post #36
krcz wrote: post #30

Earlier quoted context omitted.

Yeah, I've meant entangling 2 & 3 pair and measuring 1 & 4. But my concern is if we can still use this trick after measuring 1 & 4?

I am not sure I understand you.

I hope that can make things clear: http://imgur.com/5mfB4m0 .

Re: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

#56

Post by andrewflnr »

scotty79 wrote: post #53
andrewflnr wrote: post #40

Earlier quoted context omitted.

Personally, I've never found that a comforting alternative.

It just because people tell about it as if all the possible divergent trajectories through phase space happen not just ours. What they actually mean is that the possibilities are vast and we have no idea why reality chose exactly this path because it's not in any way priviledged. It's like a ball a top of the totally symmetric hill. If you consider phase space it contains ball rolling down in all the possible directi…

That sounds exactly like non-determinism, which is what we were trying to avoid.
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