Chinese team entangles eight photons, breaking record

In a game of one-upmanship, a Chinese team of physicists has figured out how to entangle eight photons simultaneously and to observe them in action; the previous record was six. In a paper published in arXiv, the team from the University of Science and Technology of China in Hefei, describe how they were able to convert a single photon into two entangled photons, using a nonlinear crystal, and then how they repeated that process with one of the paired photons produced, while holding the other in place, producing another pair, and then did it repeatedly until they had eight photons all entangled together, all held in place and all observable for a period of time.

First predicted by Einstein, in conjunction with two other physicists, Boris Podolsky and Nathan Rosen, entanglement (from the German word Verschränkungis) is where particles exist in a relationship so closely related, that anything that happens to one, somehow automatically happens to the other, like identical twins both feeling a pin-prick on their finger tips, whether in the same room, or miles apart.
In the new experiment, the researchers fired a photon from a high energy laser through a nonlinear crystal, causing it to become a pair of weaker entangled photons. They then kept one of the pair aside while the other was sent through another nonlinear crystal, producing another pair of entangled photons that were also still entangled with the original pair. They then held back one of the new pair while sending its twin through another nonlinear crystal, forming yet another pair of entangled photons that was also entangled with all the other entangled photons, and then repeated the procedure until they had a total of eight photons, all of which were entangled together.

After several years of research, physicists have learned a lot about creating entangled particles; what they haven’t been able to do is pin them down. Entangled particles, such as the photons produced in the Chinese experiment don’t generally last long, which makes this experiment all the more exciting because it means the researchers were able to coax the into hanging around long enough to be observed while the new entangled particles were coming into existence.

Many physicists have likened the whole process to the infamous thought experiment so named, Schrödinger's cat, due to the letter written by physicist Erwin Schrödinger to Einstein where he described a cat hidden in a box with a radioactive substance that may or may not have decayed to the point of discharging a poisonous substance that when released would kill the cat, which leads to the mind state of a cat existing that is simultaneously both dead and alive.

The ultimate goal in studying is to figure out how they operate and then how to put them to use in such devices as quantum computers.


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Quantum electronics: Two photons and chips

More information: arxiv.org/abs/1105.6318

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Jun 03, 2011
One last time. Verschränkung means 'shared enclosure' not 'entanglement'. Erwin got the translation wrong. You are just adding to the confusion. Not even in the conventional sense can 'particles' be 'entangled' by any will of the imagination.
Food for though: Maybe Erwin's English wasn't as bad as you think it was. The particles *are* "entangled" in the sense that they have shared mutually dependent, covarient properties. Also, since these properties can be shared over unlimited space, I'm not convinced that "enclosure" wouldn't be even more misleading. Erwin did not translate Verschrankung literally, and maybe that's a good thing; maybe Verschrankung wasn't the best term to begin with.

Jun 03, 2011
Oh, and one more thing. Thanks for making the point, but I'd advise against trying to turn it into a "cause célèbre" on Physorg. There's no way you are going to get Physorg staff to adopt non-standard terminology in their articles, so bringing this up every time entanglement is mentioned will end up making you look like just one more of the site's many resident cranks.

Jun 03, 2011
If you were bilingual, raised that way, in a family of nothing but theoretical physicists,
I was, but French/English, not Germany/English so I pretty much have to take your word on German semantics. And my family were mainly physicians rather than physicists :)
"Verschränkung" is the best term
Like I said, I defer to your German. From what you say I gather it's the best word in the same sense that in English "airplane" is just the best word for an, well, an airplane, with not much more contemplation required.

One final (?) thought. While "shared enclosure" might well give someone a better impression of Schrodinger's meaning in German, both it and entanglement evoke the notion of being linked together. Ultimately, though, the term used will not matter a great deal to anyone who just shuts up and calculates. In that context translation truly becomes pointless.

Jun 03, 2011
Sorry. Please discount this post.

Jun 03, 2011
Verschränkungis, Verschränkung-sin't.... So the birthday gift came wrapped in Christmas paper, what's the big deal?

Oh, wait, 'gift' means poison in German. Never mind. Any comments on the article content?

Jun 03, 2011
The way I read it 'entanglement' is a much better translation than 'shared enclosure'. (And yes, I am bilingual german/english: native german and have lived several years in the US with a background in electrical engineering - which includes a little quantum physics)

The literal meaning of 'Verschränkung' (which does include a sense of 'enclosure') is not the primary meaning you get when you think of the word in german. In german, if you use the word 'Verschränkung' you'd think more in the direction of 'having your arms crossed' or similar - which evokes the meaning of an inerlocking/mutually locked/codependent system.

In english the closest mental equvalent would be a 'gridlock' - but with only two instead of four components involved.

Jun 03, 2011
Any comments on the article content?
Ja! I think it's wonderbar. They'll probably be able to push this to a dozen entangled (ahem!) photons in short order without radically modifying their setup. And every step that we make towards developing the ability to maintain particles in an entangled state brings us closer to being able to have precise control over quantum states. So if nothing else, I hope pride will help keep them sharing their progress with the wider scientific community.

Jun 03, 2011
This is a great achievement, but I'll be more impressed when real world applications arrive. Think how great news of faster than light communications would be. Isn't this where the real world entanglements (or whatever)are headed?

Jun 03, 2011
Think how great news of faster than light communications would be.

Entanglement cannot be used for daster than light communication. For that you would have to put information into the system - in effect measuring it - which would destroy the entanglement.

Jun 03, 2011
A satellite sends a stream of photons to Earth and their entangled partners to Mars. The Mars photons are modulated in some way and the earth photons instantly modulate.

I know this is WAY beyond current tech., but just a scenario.
I'm sure some on Physorg can think of more elegant examples.

Jun 04, 2011
A satellite sends a stream of photons to Earth and their entangled partners to Mars. The Mars photons are modulated in some way and the earth photons instantly modulate.

That's the point: you cannot 'modulate them in some way' which would induce the counterpart to act accordingly.

..was going to type up an explanation but the wikipedia entry on "non-communication theorem" does a better job


Jun 04, 2011
Do you understand my way of representing this to find the best of all possible meanings?

No.

The language is quite clear and the tranlation as 'entanglement' serves its purpose (it captures the essence of what Schrödinger meant perfectly).

I think you're getting too hung up over semantics here.

Jun 04, 2011
Hush, as much as I understand that the language barrier can be a major source of misinterpretation and misunderstanding, I don't think the translation of one lousy word plays a defining role in someones ability to grasp the concept.

Either you grasp the concept and it's absolutely irrelevant how you call the "whole thing", or you don't grasp it and it is still almost absolutely irrelevant how it is called, because as a science student, you should be rather interested about how it works, rather than how it's labeled..

And as such, I also believe that the majority of confusion about "entanglement" emanates from wrong interpretation of the concept (coupled with excess imagination), rather than translation of its "labels"..

Directly from the paper:[quote]eight-photon Schrödinger cat state[/quote]Seems like our chineese colleagues have a sense of humour after all ;-D Entangled and not.

And from the article:[quote]© 2010 PhysOrg.com[/quote]Noes! The ultimate proof of timetravel! :-O

Jun 04, 2011
Hush, as much as I understand that the language barrier can be a major source of misinterpretation and misunderstanding, I don't think the translation of one lousy word plays a defining role in someones ability to grasp the concept.

Either you grasp the concept and it's absolutely irrelevant how you call the "whole thing", or you don't grasp it and it is still almost absolutely irrelevant how it is called, because as a science student, you should be rather interested about how it works, rather than how it's labeled..

And as such, I also believe that the majority of confusion about "entanglement" emanates from wrong interpretation of the concept (coupled with excess imagination), rather than translation of its "labels"..

Directly from the paper:
eight-photon Schrödinger cat state
Seems like our chineese colleagues have a sense of humour after all ;-D Entangled and not.

And from the article:
© 2010 PhysOrg.com
Noes! The ultimate proof of timetravel! :-O

Jun 04, 2011
How nice, I press [edit] to fix the broken quotes, and it reposts the whole thing as a new comment.

My apologies. Seems like the java code for [edit] is broken somehow atm :-(

Jun 04, 2011
What is the right interpretation?

The maths of it.

You can call it anyhing you want: entanglement, Verschränkung, superdeloopymagizzlfrag, ... whatever.

The things we are dealing with here are not open to perfect analogy since all our anlogies come from a macroscopic view of the world.

But analogies - for them to be useful - must be more basic than the thing you are using them as anaolgy for.

However, in this case we're going at it backwards: using stuff that is the effect of the fundamental things we are trying to describe (a macroscopic idea of stuff being 'entangled') as analogy for the fundamental principles we observe. This can only lead to confusion.

Stick to the formulae and everything will be fine.

Richard Feynman explains it best (last sentence in this video, though the rest is worth watching as a lead up):

youtube.com/watch?v=wMFPe-DwULM

seb
Jun 04, 2011
So if I understand correctly, a photon is a "wave" more or less until "observed", and then it's a "particle" on a point in that wave?

So if that is how, generally speaking, that works, what is the likely hood that "entangled particles" are really the same "wave" displaying different "observed particles" in different "locations", therefore technically "the same item"? That's all layman conceptual stuff, I know, but still, would the math support something like that?

Jun 04, 2011
The wikipedia Non-communication theorem referenced above also has an opposing viewpoint which concludes:

Zeilinger and Dopfer's experiment does not prove superluminal communication, but neither does the no-communication prohibit all forms of communication. If superluminal communication is prohibited, it is not because of the no-communication theorem. Thus, the question of superluminal communication remains open.

The wiki also references:
http://www.analog...ew.shtml

An interesting alternate view

I am willing defer to your point as being the only known observed to date. But I think you should be willing to admit the book is not completely closed on the subject.

Jun 04, 2011
As I said, this was for the last time. I will not despair. Countless contributions, useful as well as useless, are discarded daily. I have given someone "food for thought".
But it's not actually 'food' for thought is it? I mean your brain doesn't actually eat it for sustenance does it? I'm sure, like your vershrinkingtum or whatever, it's only a clever turn of phrase. There's probably a more formal word to describe it but I don't feel like looking it up. I'm sure it's there though. Wichtige Wendungen vielleicht?

Jun 04, 2011
As I said, this was for the last time. I will not despair. Countless contributions, useful as well as useless, are discarded daily. I have given someone "food for thought".
But it's not actually 'food' for thought is it? I mean your brain doesn't actually eat it for sustenance does it? I'm sure, like your vershrinkingtum or whatever, it's only a clever turn of phrase. There's probably a more formal word to describe it but I don't feel like looking it up. I'm sure it's there though. Wichtige Wendungen vielleicht?
-Although the phrase isn't really literally 'turned' is it? Because that would make it much harder to read or perhaps completely illegible. Don't you think?

Jun 06, 2011
I don't see how "shared enclosure" is good in any way at all, but that may be due to my total lack of knowledge of the actual math or even the concept itself. I'm not talking about how well it matches "Verschränkung," I'm talking about how well it matches reality.

When I think of the word enclosure, I FIRST think of an actual physical object, like a real box. Maybe "shared virtual enclosure" is better? Or "shared logical enclosure" or something else.

Since the word enclosure is a noun referring to a real material thing, it seems to me that the word "entanglement," being absent of the 'noun' attribute, is better.

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