Why is entanglement necessary for understanding quantum mechanics?

[Jabbu]

Like I said earlier, there are no 0 events in actual experiments, because only detected photons count towards the expectation value. So the sequence above seems easier to type and discuss but bears no resemblance to anything that an experiment produces, at least any experiment that has ever been performed. If you think about it, that sequence is pretty incredible. To get a sequence like that, you need to know that two photons were emitted at the same time but neither was detected in some cases, and in others that two were emitted but only one was detected. In an actual experiment you only know what was detected. If you try to measure at the source, you destroy them and invalidate the experiment. If you detect only one, you can't be absolutely sure that another one was emitted but did not go through. So the 11 case is the only certain case for matches that you can have in any experiment. And even then you have time-tagging and matching to deal with, which complicates matters even further.

Then we shall talk only about splitter polarizers where photons are detected for both 1 and 0.

If you want to see some actual experimental data, see http://people.isy.liu.se/jalar/belltiming/ which has a portion of the Weihs data.

Looks good, but they are asking for $25. Could you copy-paste some of the data for 0 degrees relative angle?

 

[Jabbu]

2. Have you not been listening to what everyone has been telling you? Photons with a specific polarization are not entangled. Once they are given a specific polarization, entangled photons are no longer polarization entangled.

I'm just asking if anyone has performed the experiment with constant photons polarization. Do you know?

 

[Jabbu]

If you want to see some actual experimental data, see http://people.isy.liu.se/jalar/belltiming/ which has a portion of the Weihs data.

Found it in "belltiming.tar.gz". That's exactly what I need. Thank you!

 

[DrChinese]

I'm just asking if anyone has performed the experiment with constant photons polarization. Do you know?

People generally don't publish null results. I am sure everyone who has done a Type I polarization experiment has seen this, since using only 1 crystal gives the effect I described (and you are asking about, which I have explained previously several times). It takes 2 crystals precisely aligned to get entanglement in the first place, else you get polarized pairs and those are not polarization entangled. I am not sure if I or anyone else can explain it any further. If you are still unsure, do the experiment yourself.

At this point, I should ask: what about "the need for entanglement" (the title of this thread) do you not understand? Entangled pairs describe a non-classical behavior as has been discussed to the Nth degree. We have explained in detail what statistics are evident and the differences with non-entangled particles.

Jabbu, my intuition tells me that we are reaching the end of the line for this thread if you are reduced to skipping study of ground-breaking experiments (numerous references provided for Weihs, Zeilinger, etc) and instead you asking about experiments providing no insight at all. (You may as well ask whether anyone has published if entanglement is different during leap years.) If you need to take this thread in a new direction, such as the discuss of raw experimental data, a new thread is in order.

 

[bhobba]

After photon A goes through polarizer A, how can photon correlation make photon B go through polarizer B with 100% chance?

The Born rule applied to Bell states:
http://en.wikipedia.org/wiki/Bell_state
http://www-inst.eecs.berkeley.edu/~cs191/sp05/lectures/lecture2.pdf

Its a logical consequence of the axioms of QM. So your question is why are the axioms of QM true? Well of course the answer to that is correspondence with experiment. But modern research has distilled it to one key assumption - see post 137:
https://www.physicsforums.com/showthread.php?t=763139&page=8
An observation/measurement with possible outcomes i = 1, 2, 3 ... is described by a POVM Ei such that the probability of outcome i is determined by Ei, and only by Ei, in particular it does not depend on what POVM it is part of.

Why is photon entanglement not part of the equation?

What do you think a Bell state being maximally entangled means? And, that being the case, why do you think photon entanglement isn't part of it?

Did you read Bell's Bertlmanns socks paper?

Thanks
Bill

 

[Jabbu]

and even then you have time-tagging and matching to deal with, which complicates matters even further. If you want to see some actual experimental data, see http://people.isy.liu.se/jalar/belltiming/ which has a portion of the weihs data.

You were right, it's like fishing with dynamite. Here's a little sample of unmatched raw data:

Alice TIME      Bob TIME        A-B
1. 0.00111168   0.0011126       0-0
2. 0.0011236    0.00114889      0-3
3. 0.00114997   0.00116779      1-0
4. 0.00115135   0.00120643      0-0
5. 0.00120123   0.00129848      1-0
6. 0.00122004   0.0013142       0-0
7. 0.00122526   0.00137652      1-0
8. 0.00124101   0.00141566      0-1
9. 0.00124709   0.00151352      3-0
10. 0.00125743  0.00152207      0-2
11. 0.00128748  0.00154191      2-0
12. 0.00131066  0.00157764      0-0
13. 0.00133157  0.0016791       1-0
14. 0.00137614  0.00177568      0-0
15. 0.00142413  0.00178678      2-0
16. 0.00147483  0.00189219      0-0
17. 0.00148506  0.00191145      2-0
18. 0.00150237  0.00196715      0-2
19. 0.00150441  0.00197128      2-0
20. 0.00151065  0.00199187      0-0
21. 0.00151289  0.00202538      2-0
22. 0.00151499  0.00205014      0-3
23. 0.00152948  0.00210897      0-0
24. 0.00155419  0.00211805      0-2
25. 0.00158218  0.00213923      2-0
26. 0.00161245  0.00216286      0-1
27. 0.00162987  0.00219944      1-0
28. 0.0016477   0.00220125      0-3
29. 0.00165599  0.00220627      2-0
30. 0.00169664  0.00225132      0-3
31. 0.00169747  0.00226738      1-0
32. 0.00171081  0.00236668      0-3
33. 0.00173233  0.00237884      3-0
34. 0.00181079  0.00241838      0-0
35. 0.00184828  0.00250185      0-0
36. 0.00187782  0.00250618      0-1
37. 0.0019019   0.00260884      0-0
38. 0.00190597  0.00261734      0-1
39. 0.0019224   0.00264896      1-0
40. 0.00197127  0.00265759      0-3
41. 0.00198946  0.00284926      2-0
42. 0.00202538  0.00287557      0-0
43. 0.00203134  0.0029057       0-0
44. 0.00203239  0.00291423      0-3
45. 0.00208354  0.00293723      0-0
46. 0.00209534  0.00294736      0-2
47. 0.00210002  0.00300586      0-0
48. 0.0021307   0.00303086      0-3
49. 0.00213906  0.00313415      1-0
50. 0.00215645  0.00315502      0-1

In about 0.001 second Alice recorded 41 detections, and Bob only 20, huh? How can there be matching photon pairs if one stream is constantly ticking at a higher rate than the other one? Also, out of hundred detections, for 0 rotation Alice recorded 66 + and 13 - detections, and for 45 rotation there was 15 + and 6 - detection. This doesn't look like 50%-50% chance to me. Perhaps I'm misinterpreting something, would you know?

 

[Jabbu]

It takes 2 crystals precisely aligned to get entanglement in the first place, else you get polarized pairs and those are not polarization entangled.

Do you know what type of crystal are those and what is it they do to make photons entangled?

 

[Nugatory]

Do you know what type of crystal are those and what is it they do to make photons entangled?

Google for "spontaneous parametric down-conversion". Typically the crystals are beta-barium oxide.

Before this (already highly derailed thread) becomes even more derailed, consider that there are several ways of creating entangled particle pairs (not necessarily photons) suitable for Bell-type experiments, multiple ways of creating polarization-entangled photon pairs, all of the experiments differ in how they're designed and analyzed, and the technology used for gathering and analyzing the data has changed greatly over the past 40 years. If you want to know exactly how a given experiment was conducted... You have to find the paper and read it.

 

[Nugatory]

In about 0.001 second Alice recorded 41 detections, and Bob only 20, huh? How can there be matching photon pairs if one stream is constantly ticking at a higher rate than the other one? Also, out of hundred detections, for 0 rotation Alice recorded 66 + and 13 - detections, and for 45 rotation there was 15 + and 6 - detection. This doesn't look like 50%-50% chance to me. Perhaps I'm misinterpreting something, would you know?

You need to look at a sample that's large enough to pick the signal out of the noise. Often only one member of the pair will be detected, and not all of the photons that make it into the detector are members of entangled pairs.

Have you tried playing around with the software that came along with that data sample?

 

[DrChinese]

Do you know what type of crystal are those and what is it they do to make photons entangled?

This is answered by the references I provided in posts #21 and #29.

As promised, Jabbu, your post has been reported.

-DrC

 

[Doc Al]

This thread has long been derailed from the initial question on entanglement. Now it seems to be going in circles regarding Bell's theorem and tests, rife with mistaken ideas, with no clear end in sight. It is time to close it.

Lots of good information (and suggestions for study) have been provided. I hope interested parties take full advantage.