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Author Topic: Are all photons already entangled?  (Read 3138 times)

Offline yor_on

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Are all photons already entangled?
« on: 13/04/2009 11:02:32 »
Thinking of entanglement I started to think that you could take two photons use a beamsplitter to entangle them, then let both of those do the exact same again but with new photons, ad infinitum. Which leads me to my new pet Q :)

Could all photons already be entangled?
How would we be able to tell if they were or wasn't??

[MOD EDIT - please try to phrase post titles as questions pertinent to the discussion topic. This helps users to locate information rapidly and also results in posts receiving more responses and more quickly. Thank you.]
« Last Edit: 13/04/2009 22:52:27 by chris »


 

Offline Vern

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Re: Are all photons already entangled?
« Reply #1 on: 13/04/2009 12:37:39 »
I think we would begin to notice that they all have the same polarization. We would not find some photons that are spin polarized and some that are polarized in fixed planes. Also I think that entangled photons have their electric and magnetic fields in the same phase. The peak amplitude of the fields happen at the same time.

 

Offline Mr. Scientist

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Re: Are all photons already entangled?
« Reply #2 on: 13/04/2009 13:09:17 »
Thinking of entanglement I started to think that you could take two photons use a beamsplitter to entangle them, then let both of those do the exact same again but with new photons, ad infinitum. Which leads me to my new pet Q :)

Could all photons already be entangled?
How would we be able to tell if they were or wasn't??

Actually, this is quite strange. Using the Luxon Theory of matter, i presumed only a couple of posts before this one that it is possible that when we create positrons and electrons from two gamma photon collisions, i prefer to state the photons the rest mass is composed of is entangled, rather than the matter itself. This would lead to every baryonic matter to exhibit internal energies that are... entangled with another photon, or three, ect ect.

So, as a theory, it certainly is allowable to have every photon entangled to another photon somewhere in spacetime, and this entanglement may give rise itself to why we have pair-production in quantum mechanics.
 

Offline Vern

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Re: Are all photons already entangled?
« Reply #3 on: 13/04/2009 15:51:45 »
In my previous post I assumed that yor_on meant that every photon was entangled with every other photon. I think we would readily notice that. However, there's nothing to oppose the notion that every photon might be entangled with another photon somewhere. But I don't think observation would support the notion that photons are always created in pairs. This would be the case in electron-position annihilation but probably not in the change of energy states in atomic electrons. 
 

Offline JP

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Are all photons already entangled?
« Reply #4 on: 14/04/2009 06:39:34 »
I think we would begin to notice that they all have the same polarization. We would not find some photons that are spin polarized and some that are polarized in fixed planes. Also I think that entangled photons have their electric and magnetic fields in the same phase. The peak amplitude of the fields happen at the same time.

This is a misconception about entanglement based on the way we usually entangle things in order to make them easy to use.  Entanglement between two photons is any case where you can't separate the quantum state of the two photons into separate states for each photon. 

Back to the original question: as far as I know its theoretically possible for all photons to be entangled.  There are even some theories that suggest that the entire universe could be one giant entangled state.  The problem is that its impractical to try to measure an entangled state for anything that isn't microscopic, since you have to keep track of all the interacting particles.  It's an open question if quantum mechanical entanglement even exists on a large-object scale (see Schrodinger's cat) since it's such a hard experiment and theoretical calculation to do. 
 

Offline Vern

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Are all photons already entangled?
« Reply #5 on: 14/04/2009 13:16:47 »
Quantum Entanglement is a difficult concept.

Entanglement of photons is straight forward and simple. Quantum Entanglement gets into the spooky realm of superposition involving collapsing wave functions to bring a particle into existence. The idea that an object does not exist until it is observed is a little difficult to accept. 

Quote from: the link
The weirdness, if you want to call it that, is the premise that the act of measurement of one actually defines both of them and so one might be thousands of miles away when you measure the first and the other instantly is converted, regardless of the distance between them, to the complement of the first.   Action-at-a-distance that occurs faster than the speed of light?

Some would argue (me for instance) that this is more of a hat trick, not unlike where a machine randomly puts a quarter under one hat or the other, and always a nickel under a second one.  You don’t know in advance which contains which.  Does the discovery that one hat has a quarter actually change the other into a nickel or was it always that way?  Some would say that since it is impossible to know what is under each hat, the discovery of the quarter was determined by the act of measuring (lifting the hat) and the other coin only became a nickel at that instant.   Is this action at a distance?
 

Offline yor_on

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Are all photons already entangled?
« Reply #6 on: 23/10/2009 04:39:59 »
Thanks jpetruccelli.

Nice description. And yeah, I should have stated it clearer Vern.
 

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Are all photons already entangled?
« Reply #6 on: 23/10/2009 04:39:59 »

 

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