Entanglement Distance: Explained for Beginners

[mikeyork]

Doesn't that overstate it?

I think of two free electrons, initially unentangled, whose trajectories pass very close to each other. They can become entangled into a singlet pair as they pass in proximity, and remain entangled as they separate.

But space and time is highly relevant. If they did not come in close proximity, they would not become entangled, hence spatial relevance. Time is relevant because there are before and after entanglement states. Future events can disentangle them, so time is again relevant.

p.s. "god idea" great pun

You have described how an external observer sees things when they impose a space-time frame. And, yes, I see your point that we can't ignore that an observer's view of the entangling interaction requires spatial coincidence (or at least proximity). But the intrinsic entanglement that results remains independent of both the observer's space-time frame and the space-time co-ordinates of each electron relative to the other.

 

[megacal]

If the Wiki article is not accurate, would like to know specifically in what way.

 

[mikeyork]

If the Wiki article is not accurate, would like to know specifically in what way.

I have responded to the two questions in your original post. I explained the problem with the piece you quoted from the Wikipedia article. I do not have the time to read the rest of the article and so I do not know how accurate it is. Even if I did have the time, I would not be inclined to do so for someone who just rolled their eyes at me as I would expect it to be a waste of my time. I suggest you spend a little more time thinking about how I have already responded and try reading a modern text-book on QM. Or, better still, since you like DrChinese's webpage, why don't you read that?

 

[DrChinese]

If the Wiki article is not accurate, would like to know specifically in what way.

No one around here really worries too much about what Wiki says in a particular part of an article. I would take what it says with a grain of salt. As Mike says, attempting to translate QM principles to lay language often leads to something that itself cannot be defended in strict terms. Think of it "as if" X is true, even if X is not strictly accurate.

 

[megacal]

Whoa, Mike!
Your answers made no sense to me, though I'm sure they are clear to
others here. You gave a very nebulous answer, imho, and did not quote any part of the article that I can see.
I don't want you to waste your valuable time on it.
Please note that I labeled the thread "B" for Basic.

Dr.Chinese,
could you please show me where the Wiki article is in error? It seemed to correlate with what I've read so
far (Louisa's book is on the way).
Thanks!

 

[megacal]

As Mike says, attempting to translate QM principles to lay language often leads to something that itself cannot be defended in strict terms. Think of it "as if" X is true, even if X is not strictly accurate.

Sorry, didn't realize you had posted...Ok, I won't beat it to death. There is nothing specifically
wrong with the Wiki article, it's just suspect because it's a Wiki article, LOL!

BTW, I don't take the Wiki as gospel for anything, but it seemed like a relatively concise explanation in this case. Always take EVERYTHING with a grain of salt..."Low Salt"...1/2 KCl, 1/2NaCl...cardio friendly.
In the Big Scheme of Things, it ain't that big a deal.
Thanks for your attempt to explain Mike's point, but I still don't get it.
Hopefully Louisa's primer on Entanglement will make it clear (assuming it has the blessing of the QM community).
Peace all.

 

[stoomart]

Whoa, Mike!
Your answers made no sense to me, though I'm sure they are clear to
others here. You gave a very nebulous answer, imho, and did not quote any part of the article that I can see.
I don't want you to waste your valuable time on it.
Please note that I labeled the thread "B" for Basic.

Dr.Chinese,
could you please show me where the Wiki article is in error? It seemed to correlate with what I've read so
far (Louisa's book is on the way).
Thanks!

I'm no doctor, but I know it's common practice for Wiki articles to cite non-peer-reviewed sources, hence why it is not considered a valid source on these forums.

 

[mikeyork]

You gave a very nebulous answer, imho, and did not quote any part of the article that I can see.

You quoted the part I referred to. I merely emphasized the importance of the first three words. Also, my first response was #20. Did you read that?

 

[megacal]

Yes, I read everything you posted, and you still have not shown me any part of the article that
you disagree with. Is your only criticism of the article the phrase, "It thus appears..."?
I'm not trying to be obtuse or argumentative. I just wanted to know what if any of the article was
wrong, according to you or anyone else.
I'm not even disputing that the article is inaccurate.
Please quote the part that is wrong, and explain why it is wrong.
Sorry I rolled my eyes...wasn't meant to be offensive.
Gotta lighten up. Life is too short.

 

[Nugatory]

Is your only criticism of the article the phrase, "It thus appears that..."?

That's not a criticism of the article, it's pointing out the words that save it and the way that you seem to have misunderstood them. If the article said

One particle of an entangled pair "knows" what measurement has been performed on the other, and with what outcome, even though there is no known means for such information to be communicated between the particles, which at the time of measurement may be separated by arbitrarily large distances.

then the article would be wrong. But instead the article carefully says that "It thus appears that...". The article doesn't say that one particle of the entangled pair knows what measurement has been performed, it says that it appears as if it does. The implication is that although it appears to be that way, it isn't really that way and everything following the "It thus appears that..." is actually false.

And stuff like this is the reason why wikipedia is not in general an acceptable source under the Physics Forums rules. There are some things that wikipedia does really well. Competent explanations of quantum mechanics is not one of them.

 

[anorlunda]

then the article would be wrong. But instead the article carefully says that "It thus appears that...". The article doesn't say that one particle of the entangled pair knows what measurement has been performed, it says that it appears as if it does. The implication is that although it appears to be that way, it isn't really that way and everything following the "It thus appears that..." is actually false.

Congratulations @Nugatory , that is an excellent explanation. It also illustrates Wikipedia's challenge and weakness. Even when the article author tries mightily to be careful and accurate, ordinary readers will miss the nuances in the choice of words. Some physics can only be described by mathematics.

 

[megacal]

ordinary readers will miss the nuances in the choice of words

Like I did.
My apologies to MikeYork for not understanding what he was pointing out earlier.
After reviewing his replies together with those of Dr.Chinese & Nugatory more carefully, and I realize I was missing the forest for the trees.
In the future I will not use the Wiki as a resource for QM (or other physics-related disciplines) to avoid the risk of being mislead or
misleading others.

In the mean time, just received my copy of The Age of Entanglement recommended by Nugatory.
According to the author, Louisa Gilder,

"This is a book of conversations, a book about how the give and take between physicists
repeatedly changed the direction in which Quantum Physics developed..."

full of quotes from memoirs & biographies.
Hope to get a better understanding of Entanglement, as well as learn about those who worked to elucidate this "spooky action at a distance"
as Einstein called it.

 

[physika]

- Quantum Entanglement, Wiki
I accept that it as reality, but how does one particle "know" what the other particle is doing or what is being done to it?
It's as though they are connected by a thread (or string?)
that has no elasticity if they react instantly to the measurement of
the other(s) in the system.

or a wormhole

Are entangled particles connected by wormholes? Evidence for the ER=EPR conjecture from entropy inequalities
Phys. Rev. D 89, 066001

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.89.066001

https://arxiv.org/pdf/1308.0289v1.pdf