Entanglement Between Photons that have Never Coexisted

  • Context: Graduate 
  • Thread starter Thread starter DrChinese
  • Start date Start date
  • Tags Tags
    Entanglement Photons
Click For Summary

Discussion Overview

The discussion revolves around the theoretical and experimental aspects of entanglement between photons that have never coexisted, specifically focusing on the implications of entanglement swapping in quantum mechanics. Participants explore the nature of entanglement, measurement, and the temporal aspects of quantum states.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that entanglement between photons that have never existed simultaneously is theoretically possible and has been demonstrated experimentally through entanglement swapping.
  • Concerns are raised about the implications of measuring photon 1 and its effect on photon 2, questioning whether photon 2 can still be considered entangled after photon 1 has been measured.
  • Others argue that entanglement swapping allows for photon 2 to remain entangled even after photon 1's measurement, emphasizing that the context of entanglement spans both space and time.
  • A participant questions whether all four photons were entangled together before any measurements were made, leading to further clarification about the nature of their entanglement.
  • Participants discuss how correlations between photons 1 and 4 can be established, noting that they exhibit correlations that suggest entanglement despite the non-existence of photon 1 at the time of measurement.
  • Some express uncertainty about the significance of these findings and whether they should be impressed by the results, indicating a lack of understanding of the implications of such experiments.
  • There is mention of a loophole in light-bound messages that could potentially allow for superluminal communication, although this is not universally accepted or explored in depth within the thread.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the implications of the experimental results and the nature of entanglement. While some support the idea of entanglement across temporal separations, others raise questions and concerns about the definitions and implications of measurement in quantum mechanics.

Contextual Notes

Participants note that the entangled state of photons can transcend normal spacetime limits, and there are unresolved questions about the implications of measuring entangled photons and the nature of their correlations.

Who May Find This Useful

This discussion may be of interest to those studying quantum mechanics, particularly in the areas of entanglement, measurement theory, and the implications of temporal aspects in quantum systems.

  • #31
Meselwulf said:
Very well, but just because he is not ''well-respected'' means nothing in the archives of physics... there have been those after all who thought the world was flat at one point and was very well-respected.

Sadly, this is a essentially a circular argument which basically leads one to assert that all opinions are equally correct.

Moot here, since that is not PF policy. Only mainstream science is allowed in the Quantum Physics section. So go elsewhere to trumpet Sarfatti, I don't see how he did anyone any favors with his views on entanglement and Bell. (Please keep in mind I criticize myself for the same kind of behavior, so I am not being hypocritical.)
 
Physics news on Phys.org
  • #32
DrChinese said:
Mais non! Quantum non-locality, an established concept, is not the same as superluminal signaling (which is not).

Do not presume sir, to think you know what QM is... in totality. QM has many hidden truths which far outweigh what we ''think'' we so audaciously believe we know... there could be a superluminal transaction... as I said... the Transactional Interpretation, a real working theory, may answer it all.
 
  • #33
Meselwulf said:
Let's understand something first... I don't believe any physical system moves faster than light. There is however another loophole, called the Transactional Interpretation... waves which can move at superluminal speeds which do not require energy to travel faster than light.

There are a number of interpretations which are out there, and I do not speak for one and against another. If you want to call such interpretations "loopholes" I guess I could see your point with that word - although interpretation is widely held to mean something else. However, not all such interpretations are considered mainstream science. Please do not confuse the word "interpretation" with "opinion" or "hypothesis" because they are not the same. And Sarfatti's "interpretation" or whatever you want to call it is not in the same league, and stretching the meaning of words will not put it there.
 
  • #34
DrChinese said:
There are a number of interpretations which are out there, and I do not speak for one and against another.

If you don't disagree with over another, then explain one fact to me... why the idea of a superluminal transfer of information... is... forbidden enough for you to threaten me with a moderator action?

I wish to talk about this, in a civilized debating way not in a way which resolves itself in a confrontational way.
 
  • #35
DrChinese said:
If you want to call such interpretations "loopholes" I guess I could see your point with that word - although interpretation is widely held to mean something else.

Well, ironic, because QM is not fully understood so what we have to deal with is interpretations, not absolutions.
 
  • #36
Meselwulf said:
Do not presume sir, to think you know what QM is... in totality. QM has many hidden truths which far outweigh what we ''think'' we so audaciously believe we know... there could be a superluminal transaction... as I said... the Transactional Interpretation, a real working theory, may answer it all.

I probably missed the part where I stated that I know what QM is. :biggrin:

And you apparently missed the part where I chose NOT to argue against the Transactional Interpretation, which I have no beef with at all. In fact, I would expect anyone familiar with it to embrace the paper which started this thread (as providing experimental support for it).

And I definitely missed any connection between Sarfatti and the Transactional Interpretation, which has nothing whatsoever to do with him. That is usually attributed to Cramer.
 
  • #37
Meselwulf said:
If you don't disagree with over another, then explain one fact to me... why the idea of a superluminal transfer of information... is... forbidden enough for you to threaten me with a moderator action?

Simple: there are no accepted interpretations supporting superluminal signaling. Asserting otherwise runs afoul of forum rules. TQM is an accepted interpretation precisely because it is functionally equivalent to sQM.
 
  • #38
Meselwulf said:
Well, ironic, because QM is not fully understood so what we have to deal with is interpretations, not absolutions.

I quite agree. But within very strict bounds. Those have been best framed by Bell.
 
  • #39
DrChinese said:
I probably missed the part where I stated that I know what QM is. :biggrin:

And you apparently missed the part where I chose NOT to argue against the Transactional Interpretation, which I have no beef with at all.

Very well.


... ;)
 
  • #40
DrChinese said:
I quite agree. But within very strict bounds. Those have been best framed by Bell.

ty... however... Since the remarkable man known as Bell... physics has known a great much more things...
 
  • #41
DrChinese said:
Simple: there are no accepted interpretations supporting superluminal signaling. Asserting otherwise runs afoul of forum rules.

Small correction: de Broglie-Bohm theory, which is an interpretation of sQM in the case of quantum equlibrium, allows superluminal signaling outside this equilibrium.
 
  • #42
good reference/paper DrChinese.

DrChinese said:
This means that photon 4 is now entangled with photon 1, even though photon 1 no longer exists!

Experimental realization of that setup shows that photons 1 and 4 violate a Bell Inequality, demonstrating their entanglement.

how is the Bell Inequality shown (experimentally) when photons 1 and 4 don't even exist?

how is an (Bell's) experiment performed on particles that no longer exist?
 
Last edited:
  • #43
San K said:
good reference/paper DrChinese.



how is the Bell Inequality shown (experimentally) when photons 1 and 4 don't even exist?

how is an (Bell's) experiment performed on particles that no longer exist?

They are measured as per usual and then a post-selection process is executed. A difficulty is to synchonize the photon arrival times so that the correct 4 are considered (since a coincidence time window must be created).

"We chose the delay length
to be the time between eight consecutive laser pulses, in
order not to lose signal due to the dead-time of the single-
photon detectors (Perkin Elmer SPCM-AQ4C), and to
provide enough time for the measurement of the first pho-
ton before the second pair is created. The delayed photon
of the first pair and the non-delayed photon of the second
pair are projected onto a Bell state by combining them
at the projecting polarizing beam-splitter (PBS) (see Fig.
2) [5]. We post-select the cases where each photon exits
this PBS at a different port. We ensure that the pho-
tons are indistinguishable, i.e., no information is available
as to whether both were transmitted or both were re-
flected."
 
  • #44
DrChinese said:
A future context affects the past (since the decision to entangle 1 and 4 is made after 4 is detected) !

http://arxiv.org/abs/1209.4191

Not sure about "Future context effecting the past" -

because (maybe)

The post selection criteria/process is such that is seems that way...but its not so.

Namely - only those photons get post selected that make it seem as if...future is effecting the past.

This is the same argument as used in Delayed choice quantum eraser.

In two words... its a "filtering trick"
 
Last edited:
  • #45
San K said:
Not sure about "Future context effecting the past" -

because (maybe)

The post selection criteria/process is such that is seems that way...but its not so.

Namely - only those photons get post selected that make it seem as if...future is effecting the past.

This is the same argument as used in Delayed choice quantum eraser.

In two words... its a "filtering trick"

The experiment agrees with quantum theory on this possibility, so are you claiming quantum theory is wrong? Or, do you believe such experiments *are* possible, but this experiment simply has flaws?
 
  • #46
RUTA said:
The experiment agrees with quantum theory on this possibility, so are you claiming quantum theory is wrong? Or, do you believe such experiments *are* possible, but this experiment simply has flaws?

FYI: You replied to an almost one year old post :wink: (not that it matters to me, but I just wanted to let you know).
 
  • #47
DennisN said:
FYI: You replied to an almost one year old post :wink: (not that it matters to me, but I just wanted to let you know).

The post that I responded to just arrived in my email this morning. I noticed it had a date from last Oct, but it said "Edited" so I guessed that it was changed last night, since I was only this morning notified.
 
  • #48
There was another new post that got deleted.
I think this thread is done.
 

Similar threads

Undergrad Entanglement swapping in the context of Indivisible Stochastic Process
  • · Replies 2 ·
Replies
2
Views
842
Graduate Is delayed choice remote entanglement of photons derived from TDSE?
  • · Replies 58 ·
2
Replies
58
Views
5K
Undergrad Construction of an Entangled Photon Source
  • · Replies 18 ·
Replies
18
Views
5K
Undergrad Delayed quantum eraser: turning off sensor to bring back interference
  • · Replies 24 ·
Replies
24
Views
4K
Undergrad After entanglement swapping, how can we verify the new entanglement?
  • · Replies 5 ·
Replies
5
Views
2K
High School The setup of "2012 entanglement between photons that (....)"
  • · Replies 25 ·
Replies
25
Views
3K
Graduate What happens when entangled photons are split into different paths?
  • · Replies 41 ·
2
Replies
41
Views
6K
Undergrad Quantum Eraser: do entangled photons arrive at different moments?
  • · Replies 1 ·
Replies
1
Views
2K
High School Quantum Entanglement Communication Radio
  • · Replies 1 ·
Replies
1
Views
2K
Graduate Can entanglement be detected in a single Bell pair?
  • · Replies 1 ·
Replies
1
Views
2K