Are entangled photons ‘touching’ in time?

martu said:
Is this opinion based on theory or experiment?
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Both. You can, for example, entangle two atoms using EM fields. The atoms were never in the same spot. That works theoretically and experimentally.

How could we know they weren't entangled?
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By measuring them.

How could you produce a pair of non entangled particles at the same point wont you violate conserved properties for the system?
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It depends what they are and how you produce them. It also depends on what you mean by "same point".

I think the idea that two or more particles can be at the same unique spot in time no matter how far apart they are could explain entanglement don't you? Completely theoretically mind you, I am well aware it seems to be wrong.
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No, to be honest I don't see how such an idea could work.
 
sol invictus said:
Both. You can, for example, entangle two atoms using EM fields. The atoms were never in the same spot. That works theoretically and experimentally.
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Can you show me a link to this experiment please?

As ever thanks again to you and RealityCheck for the use of your physics brains.
 
martu said:
Actually thinking about this a different way if it was the same photon what would it's spin be?
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An interesting point. My cursory study of this shows that entangled particles tend to have opposite spin. That might squash the usefulness of trying to think of them as the same particle co-located.
 
martu said:
No it produces entangled ions and photons it says so clearly in the text:

I take it there is something I am missing here?
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There are two entanglements that I can see.
The first is between each ion and the photon that it emited.
The second is between the ions. This is established when the "experimenters select only those excitation events that result in photons recorded by both detectors within 15 ns after the excitation".

As far as I know, the photons are not entangled with each other.
 
Reality Check said:
There are two entanglements that I can see.
The first is between each ion and the photon that it emited.
The second is between the ions. This is established when the "experimenters select only those excitation events that result in photons recorded by both detectors within 15 ns after the excitation".

As far as I know, the photons are not entangled with each other.
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Ok. When are the ions entangled before or after the photons mingle? What does the author mean by mingle anyway?
 
gnome said:
An interesting point. My cursory study of this shows that entangled particles tend to have opposite spin. That might squash the usefulness of trying to think of them as the same particle co-located.
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Exactly they have to be different.
 
(Derail)

Every time QM weirdness -- with its 11 dimensions, all hidden somewhere incredibly close to us yet untouchable, time moving backward, etc. -- is discussed, I am reminded of the old limmerick:

The creatures of other dimensions
Cause earthlings great consternation.
They can sneak up to you
And give you a screw
Before you divined their intention.
 
martu said:
Ok. When are the ions entangled before or after the photons mingle? What does the author mean by mingle anyway?
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The ions quantum states are entangled by the selection of the photon that each emit. This selection is done after the photons are detected, i.e. after they "mingle".
What the author means by "mingle" is pass through the half-silvered mirror within a 15 ns window.
If they wanted to say entangled then they would have said entangled.

ETA:
The middle column on page 17 states that the photons are entangled by the requirement that both detectors detect photons.
 
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Reality Check said:
The ions quantum states are entangled by the selection of the photon that each emit. This selection is done after the photons are detected, i.e. after they "mingle".
What the author means by "mingle" is pass through the half-silvered mirror within a 15 ns window.
If they wanted to say entangled then they would have said entangled.

ETA:
The middle column on page 17 states that the photons are entangled by the requirement that both detectors detect photons.
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Erm forgive my dumbness but doesn't your ETA contradict your original post?
 
Skeptic said:
(Derail)

Every time QM weirdness -- with its 11 dimensions, all hidden somewhere incredibly close to us yet untouchable, time moving backward, etc. -- is discussed, I am reminded of the old limmerick:

The creatures of other dimensions
Cause earthlings great consternation.
They can sneak up to you
And give you a screw
Before you divined their intention.
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If time is the 4th dimension
there is one thing I aught to mention
though this photon is here
and that photon is there
if entagled they're at one location
 
martu said:
Why is mingling required?
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To entangle the quantum state of the ions as stated in the middle column of page 17.

The experiment shows that quantum state of ions separaterd by a metre or more can be entangled The demostraion of the entanglement is described on the next page - page 18.
There is also another interesting aspect: The entanglement of the ions is establshed by causing the entanglement of photons at an arbitary distance from the ions.
 
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Reality Check said:
To entangle the quantum state of the ions as stated in the middle column of page 17.

The experiment shows that quantum state of ions separaterd by a metre or more can be entangled The demostraion of the entanglement is described on the next page - page 18.
There is also another interesting aspect: The entanglement of the ions is establshed by causing the entanglement of photons at an arbitary distance from the ions.
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Right thanks.

I contend that when the photons mingle we have the two photons and the two ions at the same point in time hence the ions become entangled. Before the photons mingle the ions are not entangled.
 
martu said:
Right thanks.

I contend that when the photons mingle we have the two photons and the two ions at the same point in time hence the ions become entangled. Before the photons mingle the ions are not entangled.
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That is right. Before the photons are mingled the ions are not entangled. If the photons are then detected within the 15 ns window the ions should be entangled. This is then demonstrated to be the case with the detection of the hyperfine state of the ions.
 
sol invictus said:
Here's an example, with links to the papers: http://blogs.discovermagazine.com/8...est-spooky-system-ever-seen-4-entangled-ions/

By the way, all the atoms in a Bose-Einstein condensate are entangled with each other, even though the condensate can be relatively large, and it can be achieved simply by cooling the atoms sufficiently.
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I read your link and it seems to infer that this entanglement involves a mechanical system. One pair of ions is set vibrating, the other pair responds. So we get back to the Mars thing again: If I set two ions vibrating on Earth, two entangled particles do likewise on Mars. Why is this not an instantaneous switch?
 
sol invictus said:
Here's an example, with links to the papers: http://blogs.discovermagazine.com/8...est-spooky-system-ever-seen-4-entangled-ions/.
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From your link:

The first step to achieving these synchronized vibrations relied on standard techniques to entangle the spins of the beryllium ions in each pair.
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What are these standard techniques? Do they involve bringing the entangled pairs together at one point in space and time?

sol invictus said:
By the way, all the atoms in a Bose-Einstein condensate are entangled with each other, even though the condensate can be relatively large, and it can be achieved simply by cooling the atoms sufficiently.
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From this paper Entanglement concentration in Bose-Einstein condensates

Since entanglement cannot be created by local operations on separate systems, entangled pairs of systems need to be created at a source and then distributed to distant parties.
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Bose-Einstein condensates fit my picture as you have to ‘distribute’ the entanglement which I would say is bringing two particles together at the same point in time then doing this over and over again resulting in all the atoms sharing a point in time.
 
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