Quantum physicists shed new light on relation between entanglement and nonlocality

Jan 30, 2012

(PhysOrg.com) -- New research from the University of Bristol may disprove a long-standing conjecture made by one of the founders of quantum information science: that quantum states featuring ‘positive partial transpose’, a particular symmetry under time-reversal, can never lead to nonlocality.

When it comes to space and time, modern physics defies our intuition in the most dramatic way.  Einstein's relativity theory tells us that time and space are intimately related and that absolute time is an illusion.  Quantum mechanics, however, is at rest, and its predictions are perhaps even more astonishing than those of relativity.

In a nutshell, quantum theory tells us that two entangled particles behave as a single physical object, no matter how far apart they are.  If a measurement is performed on one of these particles, the state of its distant twin is instantaneously modified.

This effect leads to quantum , the fact that the correlation between results of local measurements performed on these particles are so strong, that they could not have been obtained from any pair of classical systems, such as two computers.  To cut a long story short, it is as if quantum particles live outside space-time – and experiments confirm this.

Understanding this phenomenon of quantum inseparability, arguably the most counter-intuitive feature of the theory, represents a major challenge of modern physics.  A key point is that inseparability appears under various forms in quantum mechanics.  Understanding precisely the relation between these various forms is a long-sought-after goal.

Writing in , Dr Tamas Vertesi from the Hungarian Academy of Sciences and Dr Nicolas Brunner from the University of Bristol make a significant step forward in this direction.  They show that  the weakest form of – so-called undistillable entanglement – can lead to quantum nonlocal correlations, the strongest form of inseparability in .  According to Professor Pawel Horodecki, a quantum theorist at the Gdansk University of Technology, “entanglement is almost ‘invisible’ in such systems, which makes it very surprising that they can exhibit nonlocality”.

The work of Dr Vertesi and Dr Brunner also goes a long way towards disproving a long-standing conjecture made in 1999 by Professor Asher Peres, one of the founders of science.

Peres argued that quantum states featuring a particular symmetry under time-reversal – known as partial transpose – can never lead to nonlocality.  All research in this area supported Peres’ conjecture – until now.  Vertesi and Brunner’s work proves, via a simple example, that the conjecture is false when three (or more) observers are present.  It remains to be seen whether the conjecture could nevertheless hold true in the case of two observers.

Alongside its contribution to our understanding of the foundations of quantum theory, this work raises novel questions in .  In particular, it will spark a debate on the role that entanglement and nonlocality play in quantum information processing tasks, such as in quantum cryptography and computation.

Explore further: Physicists design quantum switches which can be activated by single photons

More information: 'Quantum nonlocality does not imply entanglement distillability', by T. Vertesi and N. Brunner in Physical Review Letters 108, 030403 (2012). prl.aps.org/abstract/PRL/v108/i3/e030403

Related Stories

The age of quantum information

Sep 15, 2011

Today’s computers, which are based on classical mechanics, process information coded in long streams of 1s and 0s.

Matter-matter entanglement at a distance

May 27, 2011

(PhysOrg.com) -- Scientists at the Max Planck Institute of Quantum Optics prepare quantum mechanical entanglement of two remote quantum systems.

Recommended for you

Progress in the fight against quantum dissipation

Apr 16, 2014

(Phys.org) —Scientists at Yale have confirmed a 50-year-old, previously untested theoretical prediction in physics and improved the energy storage time of a quantum switch by several orders of magnitude. ...

User comments : 35

Adjust slider to filter visible comments by rank

Display comments: newest first

Noumenon
1.6 / 5 (21) Jan 30, 2012
When it comes to space and time, modern physics defies our intuition in the most dramatic way.


Because space, time, and causality are a-priori conceptual intuitions of the mind. They are not observable entities themselves, but are the form in which experience must take given evolved a-priori intellectual faculties of the mind. (how the mind operates on, and organizes sense experience).

An intuitive understanding of reality implies that reality was forced to conform within this subjective conceptual structure,.. this leads to inconsistencies as reality is misrepresented in this relatively arbitrary and artificial form (from macro to qm scale). The minds intuitive faculties simply don't function consistently on the qm level. This implies that the underlying reality (to qm) cannot ever be intuitively understood. Positivism prevails over realism.

[this post was made to annoy GhostOfOtto]
rawa1
1 / 5 (13) Jan 30, 2012
The concepts of weak and strong entanglement can be understood with AWT, the water surface model in particular. The water surface plays an analogy of the space-time, the directions parallel with water surface are space dimensions, the remaining direction perpendicular to it is the time dimension.

At the water surface the observable objects are represented with solitons or wave packets, which can interact with both surface waves, both underwater waves. The mutual interaction with surface waves is easy to handle both mathematically, both experimentally, because just the surface waves are directly observable for us in the same way, like the transverse waves of light. But the mutual interaction trough longitudinal waves is something, which cannot be described with surface waves at all, so that only indeterministic, statistical approach of quantum mechanics has been developed here.

Nevertheless in context of dense aether model, these interactions are as real, as these observable ones.
Telekinetic
1 / 5 (5) Jan 30, 2012
"The minds intuitive faculties simply don't function consistently on the qm level. This implies that the underlying reality (to qm) cannot ever be intuitively understood."- Noumenon
And I say that all depends on WHO is intuitively understanding. I suggest you read the work of David Deutsch before you say never.
I am lodging a formal complaint to the editors of PhysOrg for pulling Erik D.Andrulis' paper 'The Theory of the Origin, Evolution, and Nature of Life. It was pulled by Case Western and in an act of censorship, Physorg followed suit without a mention of its reasons for retraction. Andrulis' work is controversial but no more so than much of QM. I commented on the similarity to the reaction to Wilhelm Reich's books, which were burned in the 1950's by the F.D.A.! Overnight, the paper by Andrulis disappeared, making me realize you don't have to burn anyone's newly published ideas anymore, just the touch of a button will erase all traces of it. Shame on PhysOrg!
encoded
5 / 5 (10) Jan 30, 2012
Or maybe 'The Theory of the Origin, Evolution, and Nature of Life' was just pseudo-science and pantheism written by hippies, even more useless than neutron repulsion.
Moebius
1.8 / 5 (5) Jan 30, 2012
When it comes to space and time, modern physics defies our intuition in the most dramatic way.


Not really, modern physics has a lot to learn about space and is still clueless about time.
Noumenon
1 / 5 (15) Jan 30, 2012
"The minds intuitive faculties simply don't function consistently on the qm level. This implies that the underlying reality (to qm) cannot ever be intuitively understood."- Noumenon

And I say that all depends on WHO is intuitively understanding. I suggest you read the work of David Deutsch before you say never.

I will have to look into that. However, the many-worlds interpretation doesn't solve the measurement problem, and still requires a conscious observer to differentiate one possible world from another,.. but I'm not aware of his point.
Telekinetic
1 / 5 (1) Jan 30, 2012
Or maybe 'The Theory of the Origin, Evolution, and Nature of Life' was just pseudo-science and pantheism written by hippies, even more useless than neutron repulsion.
-encoded
Here's a patent application from the "hippie" Erik D.Andrulis :
A method for preparing a cross-linked nucleic acid-protein complex; the method comprisingcontacting a cell with a stabilizer at a concentration and for a period of time effective for stabilizing protein-chromatin complexes, the concentration and the period of time being selected for specific stabilization of the interactions between chromatin proteins and chromatin; andisolating protein-chromatin complexes from the cell, the isolated protein-chromatin complexes forming the chromatome.
Now that we know Andrulis can run circles around you, encoded, consider making a retraction of your own.

Read more: http://www.faqs.o...kxYH7vh5
ECOnservative
3.7 / 5 (6) Jan 30, 2012
nonlocalamity: When the same bad thing happens simultaneously in different places with no obvious other connection.
Deathclock
4.6 / 5 (10) Jan 30, 2012
We perceive reality in the way that best suits us. As with physical features, I would argue that our very perception of reality was likely selected for by natural selection. Can you imagine if we had microscope eyes, seeing 500x magnification compared to what we see now but only 1/500th of the field of view? That would change our perception of reality immensely, but it would also cripple us and leave us susceptible to predators and self injury.

My point is, our perception of reality leads to what we consider "intuitive", but that perception of reality is not reality, so reality itself should not be expected to be intuitive.

I'm dubious that "time" is anything but a conceptual framework... our brain remembers things in order, and can imagine the future, and that gives us the impression of time. In reality the past and future do not exist, only the present.
Callippo
1.5 / 5 (8) Jan 30, 2012
In reality the past and future do not exist, only the present.
I don't share such a nihilistic stance, particularly because it introduces a restrictions - but it doesn't reciprocate us with any predictions. In this sense my way of thinking is strictly economical: if I don't require some assumption for anything, I don't handle it. BTW In quantum mechanics the future exists in extradimensions: the quantum wave "knows", where to emerge and the past "exists" there as well.
MrVibrating
1 / 5 (1) Jan 30, 2012
I'm dubious that "time" is anything but a conceptual framework... our brain remembers things in order, and can imagine the future, and that gives us the impression of time. In reality the past and future do not exist, only the present.
There's temporal information, and spatial - or sequential and simultaneous. But relativity tells us simultaneity's impossible, and cogsci tells us spatial info is dependent on temporal integration windows, where info sampled within the time constant is 'spatial' and the rest, temporal. So it's not time that's the stubbornly persistent illusion at all.. but space. Objectively, there IS only temporal information.
Callippo
1 / 5 (2) Jan 30, 2012
But relativity tells us simultaneity's impossible, and cogsci tells us spatial info is dependent on temporal integration windows
Yep - and so what? The quantum mechanics is based on deep simultaneity instead and the observable reality is a deep hyperdimensional mixture of both theories, which are heavily violated mutually just at the human observer scale. (Nearly) nothing what you may say about relativity is relevant at the quantum level and vice versa - so it cannot be generalized at all.
Seeker2
1 / 5 (1) Jan 31, 2012
The minds intuitive faculties simply don't function consistently on the qm level.
Nothing functions consistently on the qm level.
This implies that the underlying reality (to qm) cannot ever be intuitively understood.
Yes unless it might be possible to understand uncertainty.

Positivism prevails over realism.
Uncertainty prevails over determinism.
Seeker2
1 / 5 (1) Jan 31, 2012
Andrulis' work is controversial but no more so than much of QM.
I'd be interested in hearing more about the QM controversy.
Cynical1
1 / 5 (1) Jan 31, 2012
Interesting, most of what you all are saying here is way past my comprehension threshold. Maybe not that I can't - maybe just don't want to expend energy on it. For some odd reason I am reminded of the Hitchhikers guide "Infinite probability" ship.
Anyway, our entire human existance is representative of QM. A good analogy is - your wife when she goes menopausal. Her "inconsistancies" are something you have to deal with, too. Locality of a sort...
Seeker2
1 / 5 (1) Jan 31, 2012
In reality the past and future do not exist, only the present.
Memory, I believe, is part of the present. I see no problem connecting the past with current memory.
Cynical1
1 / 5 (1) Jan 31, 2012
I believe memory is part of an undeveloped sense that eventual evolutionary design (and I use that term in the loosest way) will one day allow us to actually move between the different locales of each planck moment in the universe(ie - time). I beleive it is layered - sort of like an onion - each layer a planck length and a planck time segment apart. Each layer is ALWAYS there. This would also explain the increasing expansion of the universe in an elegantly simple way. I just need a super-computer to crunch the numbers...

After all, I am a gyre (actually spelled geier)... Kind of a sideways shout out to Doc Andrulis. And, BTW - we're ALL gyres...
Seeker2
1 / 5 (1) Jan 31, 2012
But relativity tells us simultaneity's impossible,
I suppose that's because of the misunderstanding about gravity propagating at the speed of light. Which it does. But once propagated it moves instantaneously with a non-accelerating particle. Note most of it was propagated during inflation, when the distances between particles was very small and essentially all matter became almost instantly in gravitational communication. Non-accelerating particles carry with them their gravitational fields. So they interact instantaneously to each other's field.
Seeker2
1 / 5 (1) Jan 31, 2012
Identically accelerating particles would be in almost instantaneous communication if their separation is small.
Cynical1
1 / 5 (1) Jan 31, 2012
So this would add weight to my theory. If 2 particles were at one time quite close, they are "remembering" that fact and actually somehow bringing that prior closeness to THIS layer of the Planck "onion"
Seeker2
1 / 5 (1) Jan 31, 2012
So this would add weight to my theory. If 2 particles were at one time quite close, they are "remembering" that fact and actually somehow bringing that prior closeness to THIS layer of the Planck "onion"
You might say they leave a lasting impression on each other. Actually all matter created during inflation would seem to do that. Like you just can't go back and unpeal the onion.
Seeker2
1 / 5 (1) Jan 31, 2012
This would also explain the increasing expansion of the universe in an elegantly simple way.
Do you mean the accelerating expansion? That would be a good trick. I suspect the expansion in all directions is directly tied to the passage of time in both forward and backward directions. That's a consequence of Einstein's ideas about spacetime, but I don't think he thought of all its consequences.
rawa1
1 / 5 (2) Jan 31, 2012
..gravity propagating at the speed of light. Which it does. But once propagated it moves instantaneously with a non-accelerating particle..
???
Noumenon
1.3 / 5 (16) Jan 31, 2012
..gravity propagating at the speed of light. Which it does. But once propagated it moves instantaneously with a non-accelerating particle..


Gravity cannot exceed the speed c, so "instantaneously" is the wrong word here. You're confusing static gravitational fields with gravitational waves. This is explained in the link below, paragraph 3 to 5.

http://en.wikiped..._gravity
Seeker2
1 / 5 (2) Jan 31, 2012
..gravity propagating at the speed of light. Which it does. But once propagated it moves instantaneously with a non-accelerating particle..


Gravity cannot exceed the speed c, so "instantaneously" is the wrong word here. You're confusing static gravitational fields with gravitational waves.
Yes instantaneous is the wrong word for propagation. The propagation cannot exceed c. Once propagated, the static field moves with a non-accelerating mass. It essentially becomes part of the non-accelerating mass. If this doesn't explain the question I can design an experiment for you which illustrates the instantaneous idea for static fields (of non-accelerating masses), if you wish.
THE_ANTIPHILO
1.7 / 5 (6) Jan 31, 2012
When it comes to space and time, modern physics defies our intuition in the most dramatic way.


Because space, time, and causality are a-priori conceptual intuitions of the mind. They are not observable entities themselves, but are the form in which experience must take given evolved a-priori intellectual faculties of the mind. (how the mind operates on, and organizes sense experience).

An intuitive understanding of reality implies that reality was forced to conform within this subjective conceptual structure,.. this leads to inconsistencies as reality is misrepresented in this relatively arbitrary and artificial form (from macro to qm scale). The minds intuitive faculties simply don't function consistently on the qm level. This implies that the underlying reality (to qm) cannot ever be intuitively understood. Positivism prevails over realism.

[this post was made to annoy GhostOfOtto]
Well THIS is obvious crap.

Hey nou whats with your great manifold of upraters?
Callippo
2 / 5 (4) Jan 31, 2012
Well THIS is obvious crap.
If it would be so obvious, you would give us some apparent reason for your stance already. But you didn't, which indicates, such evidence isn't so straightforward and obvious, as you're trying to pretend.
Seeker2
1.5 / 5 (2) Jan 31, 2012
Andrulis' work is controversial but no more so than much of QM.
Like when Einstein proposed his hidden variables theory to explain uncertainty? I guess the controversy just goes on.
Callippo
1 / 5 (5) Jan 31, 2012
The fact is, we have surface water analogy for nearly all significant quantum effects, like the tunneling, orbitals, double-slit experiment or Hawking radiation - so that the ignorance of dense aether model becomes a sort of religious stance, because the connection of quantum mechanics and AWT is quite apparent. The question rather is, how many water surface analogies the deniers of AWT would still require?
Cynical1
1 / 5 (1) Jan 31, 2012
I'm dubious that "time" is anything but a conceptual framework... our brain remembers things in order, and can imagine the future, and that gives us the impression of time. In reality the past and future do not exist, only the present.
There's temporal information, and spatial - or sequential and simultaneous. But relativity tells us simultaneity's impossible, and cogsci tells us spatial info is dependent on temporal integration windows, where info sampled within the time constant is 'spatial' and the rest, temporal. So it's not time that's the stubbornly persistent illusion at all.. but space. Objectively, there IS only temporal information.

Objectively, there is only information - no matter what stick you use to measure it...
Isaacsname
1 / 5 (1) Feb 04, 2012
Hey...did you guys know my uncle was Detlev Wulf Bronk ( MJ-12 ) and my mom worked in a virology program under him at John Hopkins University when she was pregnant with me...but I don't know who my father is ?

Do you know who Grigori ( George ) Yitshak (!saac )fallen from the House of David is ?

http://lunaticout...than-you

*bag over head*
Smashin_Z_1885
not rated yet Feb 06, 2012
I am becoming increasingly exhausted by all the speculations concerning not only this specific topic, but also 'time travel', because I have been involved with so many projects and suffered the inevitable psychological issues inherent in such experiments, that I am ready to throw my hands up now. I know there is no way that I can prove it one way or the other; all I can say is that we have done this over and over again successfully. So yes, it's not only possible, but quite efficient as well. But now I am finished with it as my mind can take no more of it and remain sane. That is all I have to say, and I hope that you scientists, and everyone else who is pursuing this field, will eventually experience it firsthand. Only then will you ask the next question "what is real?" Because once you experience it for yourself, that will be your first question, "how?". Then all of 'reality' becomes an even bigger question with even more unanswered questions. It's infinite I think.
Cynical1
1 / 5 (1) Feb 06, 2012
Yes instantaneous is the wrong word for propagation. The propagation cannot exceed c. Once propagated, the static field moves with a non-accelerating mass. It essentially becomes part of the non-accelerating mass. If this doesn't explain the question I can design an experiment for you which illustrates the instantaneous idea for static fields (of non-accelerating masses), if you wish.

The word "Propagation" indicates a sequential chain of events, a discripter of causality - ie.; - to change state upon the occurance of a previous event. Hence "simultaneous" does not apply.
Kinedryl
1 / 5 (1) Feb 06, 2012
The propagation cannot exceed c.
Quantum wave doesn't propagate. It can emerge suddenly somewhere else and this emergence is instantaneous. Only group velocity cannot exceed the speed of light. It means, until the motion of quantum wave doesn't affect the center of mass location, it can undulate with superluminal speed quite easily across large area. QM postulate just maintains, the integral of the wave function across the whole area remains unitary, but there is no any constrain for speed, in which the distribution of probability density changes over this area. It means, the QM has a superluminal propagation hardwired in it - without it it couldn't maintain the integral of the probability density unitary over the larger area. The quantum wave somehow "knows", if we remove it density at one place, at some other place the same density must be added simultaneously.

http://www.youtub...D0Ka6TsY
Kinedryl
1 / 5 (1) Feb 06, 2012
This is just the trick of entangled pair formation, when two objects do share their common wave function. If we change the state of one object in the entangled pair, then the same state of the second member will change accordingly in the opposite way. So until pair of photons remains entangled and we switch the spin of one of this photons, then the spin of the another photons will change accordingly at the same moment - no matter, how this 2nd photons is actually distant. It's similar to the behavior of long lever in balance, which is behaving like infinitely rigid body as a whole. In relativity the state of both ends of such lever cannot change simultaneously, their changes will propagate along lever like (gravitational) wave with speed of light. In quantum mechanics such restriction doesn't apply and the change of the second end will appear simultaneously.

More news stories

Atom probe assisted dating of oldest piece of earth

(Phys.org) —It's a scientific axiom: big claims require extra-solid evidence. So there were skeptics in 2001 when University of Wisconsin-Madison geoscience professor John Valley dated an ancient crystal ...