'Quantum magic' without any 'spooky action at a distance'

Jun 24, 2011
The central part of the optical setup used to demonstrate that even a system which does not allow entanglement exhibits features commonly attributed to this phenomenon. Credit: IQOQI; Jacqueline Godany 2011

The quantum mechanical entanglement is at the heart of the famous quantum teleportation experiment and was referred to by Albert Einstein as "spooky action at a distance". A team of researchers led by Anton Zeilinger at the University of Vienna and the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences used a system which does not allow for entanglement, and still found results which cannot be interpreted classically. Their findings were published in the latest issue of the renowned scientific journal Nature.

Asher Peres, a pioneer of quantum information theory once remarked jokingly in a letter to a colleague (Dagmar Bruß): Entanglement is a trick 'quantum magicians' use to produce phenomena that cannot be imitated by 'classical magicians'. When two particles are entangled, measurements performed on one of them immediately affect the other, no matter how far apart the particles are. What if, in an experiment, one considers a system that does not allow for entanglement? Will the quantum magicians still have an advantage over the classical magicians?

Quantum physics beyond magic

This is the question the team of quantum physicists led by Anton Zeilinger from the Faculty of Physics at the University of Vienna and from the IQOQI of the Austrian Academy of Sciences addressed in their experiment. The physicists used a "qutrit" – a quantum system consisting of a single photon that can assume three distinguishable states. "We were able to demonstrate experimentally that quantum mechanical measurements cannot be interpreted in a classical way even when no is involved," Radek Lapkiewicz explains. The findings relate to the theoretical predictions by John Stewart Bell, Simon B. Kochen, and Ernst Specker.

Quantum world versus everyday life

Quantum physics is in stark contrast with what we perceive and experience in our everyday lives and what we understand as "classical physics". Let us, for example, examine a globe: from a given point of view we can only see one respective hemisphere at any given time. When spinning the globe once around its axis we are able to construct a meaningful and "true" picture of our planet assuming that the shape of the continents stays the same, even when we cannot see them.

Therefore, by means of our experience and the assumptions made in classical physics, we can assign certain properties to a system without actually observing it. This is no longer the case if one pictures a "quantum globe". Contrary to a globe where –due to the assumptions of classical properties– the various pieces fit together as they do in a puzzle, the pictures of the quantum globe do not fit together. Yet the pattern is not random: it is possible to predict by how much the individual parts will differ from each other after an observation.

Explore further: Quantum physics just got less complicated

More information: Experimental non-classicality of an indivisible quantum system, Radek Lapkiewicz, Peizhe Li, Christoph Schaeff, Nathan K. Langford, Sven Ramelow, Marcin Wiesniak and Anton Zeilinger, Nature, June 23, 2011. DOI: 10.1038/nature10119

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NotAsleep
2.7 / 5 (6) Jun 24, 2011
"When two particles are entangled, measurements performed on one of them immediately affect the other, no matter how far apart the particles are."

It's wording like this that drives people to believe quantum entanglement is more than it really is... measuring one will not change the other. It will merely add a piece of information to the other that was unmeasured previously
Tachyon8491
2.9 / 5 (7) Jun 24, 2011
This article is seriously incomplete - apart from no insightful information given about the apparatus involved, more seriously, no mention is made of factual symptoms observed in parameters revealed by experimental comparison of the two (classical and non-classical) systems. Paradoxically, I presume we can now refer to "non-entangled entanglement" - simply, and axiomatically accepting that there is nothing which is not mutually sensitive. Interestingly this is an age-old memetic truism already assumed by the "Twelve Nidhanas" - the Buddhistic metaphysical axiom of "interdependent origination." Sometimes science lags behind by a few millennia..
c0y0te
5 / 5 (2) Jun 24, 2011
@NotAsleep
I am not a physicist, but from what I read it is much more complex than that. Don't get me wrong, but do you think that you are the first one that has thought of a hidden "unmeasured" information?!? (check Bell's inequality theorem if you haven't already)
Although, I must say that I've always deeply felt that universe is totally deterministic, and as I have recently found out Gerard 't Hooft disputed the validity of Bell's theorem in such universe. So, if I understand it right, if there is a hidden variable then the universe must be superdeterministic.
NotAsleep
3 / 5 (4) Jun 24, 2011
It's possible that the future will change our understanding of time. I'm hopeful that someday we discover some force or particle that travels faster than the speed of light. If discovered, it might have the ability to transmit useful information to another object at speeds greater than "c". With our current view on time, this would mean we can see something happen before it happens.

I agree that our current understanding of time is flawed but only to the extent that we haven't found anything that can transmit information faster than "c". It's this discussion on what constitutes "information" that has popped up in three posts this week. Something doesn't exist until it exists (duh). Along those lines, something can't exist unless it can be measured. Therin lies the limitations of our current knowledge. Just because we don't have the ability to measure something doesn't mean it CAN'T be measured. My issue is that the article makes unusual statements without explaining them
NotAsleep
1 / 5 (3) Jun 24, 2011
They used the term "affect", which to a casual reader might imply that one particle has a physical interaction with the other across any distance. As we understand physics, this isn't how it works. Assigning a piece of information to something does affect it but it is not the incredible phenomenon that the article makes it out to be
stealthc
3.6 / 5 (7) Jun 24, 2011
Everything is already entangled, our observation of which is merely isolation of elements from the already entangled system. See instead of it happening out of the blue, when you isolate it local entanglement effects begin to take over the less-local entanglement effects (such as particle transmissions of various sorts). If it's in things predicted not to have them, then this is probably the 40,000th time I've mentioned my theory, maybe this time it won't be falling on a lot of deaf ears. Everything is already entangled, it's like the glue in the spider web that creates the mesh structure.
SteveL
2.5 / 5 (2) Jun 24, 2011
"I'm hopeful that someday we discover some force or particle that travels faster than the speed of light. If discovered, it might have the ability to transmit useful information to another object at speeds greater than "c". With our current view on time, this would mean we can see something happen before it happens."

Is that really our view? I'd think that speeds greater than light would simply mean faster than light. There is a gap between the speed of light and instantaneous. In that gap I don't see how effect could preceed cause.
seb
4 / 5 (1) Jun 24, 2011
I think it's not about "measurement information" being transmitted faster than light, but rather that the notion of there being any space in between say, two entangled particles, is a flawed human concept, and that perhaps until something acts on it, they are not "two" different items at all, but rather some sort of "reflection" of one item.

NotAsleep
2.5 / 5 (4) Jun 24, 2011
@ stealthc, I believe that someday we'll have a better understanding of what gravity really is, after which your thoughts will carry more weight.

@ steveL, Yes, that's what our view is mostly because we haven't been able to observe any evidence to the contrary. I understand what you're saying but you need to put it in the frame of information theory, which essentially says we perceive things happening in relation to the fastest particle of information that the event emits. This absolutely leaves the door open to change our understanding of time.

@ seb, ok, but what use is that to us? They're developing applications for cryptography but that's about the limit. Imagining the particles as being "the same" is a good visualization but, unless we have a breakthru in physics, it isn't reality
TabulaMentis
2 / 5 (3) Jun 24, 2011
@Stealthc:
Everything already being entangled makes sense after reading this article. What theory is it that you speak of?
seb
5 / 5 (1) Jun 24, 2011
@ seb, ok, but what use is that to us? They're developing applications for cryptography but that's about the limit. Imagining the particles as being "the same" is a good visualization but, unless we have a breakthru in physics, it isn't reality


There's 0 reason to assume they are "different particles" either, yet we jump to that conclusion because we are used to thinking in such ways. Quantum level physics seems to need some serious thinking outside of the box to make heads and tails of.

One way they can be the "same item" even if they are "different particles" is if the "potential wave" of both is literally the same wave, that only collapses into "different particles" when a measurement is taken - one item becomes two items of the same values traveling along the local path of that part of the wave function, so to speak, because the act of measuring has caused an alteration.. Make any sense?

SteveL
3.8 / 5 (4) Jun 24, 2011
The only way cause can follow effect is to be faster than instant - faster than zero time. 200,000 miles per second is not faster than zero time and is significantly slower than instant. Yes, 200,000 miles per second is faster than light and is faster than any method we have to communicate that cause.

There are supernovas that have already occoured, we just don't know it yet because the light or radiation hasn't reached us. Just because we don't know it, does not mean it hasn't happened.
emsquared
1 / 5 (1) Jun 24, 2011
Absolutely not a physicist here, so sorry if this is a stupid question, but I'm wondering does this have implications for quantum computing? Like more capacity for information transfer from a single qubit or anything? Or is this just a commentary on the nature of quantum mechanics or...?
loreak
5 / 5 (3) Jun 24, 2011
This seemed like a very poorly written article, lacking anything conclusive or even a point.
NotAsleep
not rated yet Jun 24, 2011
@ steveL, agreed. It's like the "tree falling in the woods" question: If a star goes supernova in another part of the universe and no radiation has yet reached earth, did it really happen?

@ emsguared, not only is it probably too early to tell but, as loreak says, the article did a really bad job at making any particular point

@ seb, I'm not disagreeing with your statement, although I think it's just semantic jousting. I can understand the argument that they remain as the same particle just like I can understand the argument that fire and crystals are living organisms
George_Rodart
3.7 / 5 (3) Jun 24, 2011
Here's a link to a better article
http://www.scienc...ce-80335
jjoensuu
1 / 5 (3) Jun 24, 2011
Another issue is that just because some action at a distance seems "instant" does not mean that it in reality was "instant". It could have just been sufficiently fast for us to be unable to measure the speed. In other words, not 0 time, but like 9.1093822×10^31 time or something like that.
holoman
not rated yet Jun 24, 2011
only talking about photons.

tigger
3 / 5 (2) Jun 24, 2011
What if the universe is operating in a clockwork fashion, but it can't be determined because we're inside and part of that system... we, the observers are part of the system itself... part of a system that is fundamentally clockwork and not at all weird and nonsensical in the way quantum physics is so often presented.

Agree very much with StealthC... the entire system is entangled, we like to think we can draw a circle around things and say "that's an isolated experiment and nothing outside influences it"... I think that's a flawed premise. We do what we can as observers within the system... but for so so many years I've been baffled at the magic powers physicists seem to give this observer, which is just another collection of atoms within the same system.
Vendicar_Decarian
5 / 5 (5) Jun 24, 2011
Wow.. This article is completely devoid of content.

I wonder how long it took to scrub all the meaning out of it.

hush1
1 / 5 (1) Jun 24, 2011
Great efforts are made to assign the concept 'location' an absolute meaning. Location has to be relative to anything imagined.
The classic aid to location is dimensionality.
Information(here)is used without reference to location.
Establishing location using any form of reference adds information to any concept under consideration.
Deesky
5 / 5 (3) Jun 25, 2011
I think it's not about "measurement information" being transmitted faster than light, but rather that the notion of there being any space in between say, two entangled particles, is a flawed human concept, and that perhaps until something acts on it, they are not "two" different items at all, but rather some sort of "reflection" of one item.

Two entangled particles are in a sense a single unit - they share the same quantum state. But they can nevertheless be physically separated by vast distances, and yet the act of measuring one will instantaneously affect the other (though no information can be thus communicated). But explaining the effect away by saying the particles are just a single system, even though they could be separated by light years of distance, doesn't explain away the spookiness of it all.
hush1
1 / 5 (2) Jun 25, 2011
"Entanglement" I believe is a translation misnomer. If you are bilingual (German/English, English/German), you will 'know' equivalency between the translation of the 'concept' does not exist.

Languages using words are never equivalent. Equivalency among the words of all languages implies redundancy, not extension.
(The conclusion leads to only one outcome - Only one (worded) language is needed to expression any concept completely.)

All translation morphs meaning.
And I refuse to make probability wear the shoe of causality.
scikud
not rated yet Jun 26, 2011
I remember the days when people wrote articles with actual content.

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