Physicists Propose Method for Entangling Moving Material Particles

Jan 16, 2009 By Lisa Zyga feature
The proposed set-up for entangling the motion of material particles. A diatomic molecule is exposed to a sequence of two magnetic pulses, so that each of the two particles is characterized by an early and a late wave packet component resulting from two different dissociation times. A simple position measurement determines their correlation, which is called “dissociation time entanglement.” Image credit: Gneiting and Hornberger.

(PhysOrg.com) -- When physicists experiment with quantum entanglement, they usually work with photons, the intangible particles of light. In the past few years, however, scientists have begun to broaden their experiments by entangling material particles. By seeing how far this quantum property extends into the classical realm, researchers can investigate the implications of entanglement in the macroscopic world, such as our intuitive assumptions of “realism” - that objects exist whether or not anyone observes them - and “locality” - that objects cannot communicate with each other faster than the speed of light.

In a recent study, physicists Clemens Gneiting and Klaus Hornberger from the Ludwig-Maximilians-University of Munich in Germany have proposed a scheme to take entanglement one step further: they explain how to entangle the motion of two macrosopically separated particles. Rather than resorting to entangling the internal states of the particles, the physicists suggest using a pulsed magnetic field to spatially separate the particles’ wave functions. Then, an interferometer can detect the correlation between each particle’s two separated wave packets, demonstrating what the scientists call “dissociation time entanglement” (DTE).

As the physicists explain, entangling the motion of massive particles could have certain advantages compared with entangling their internal states. “In contrast to spin, motion - or rather position - has a direct classical analogue,” Gneiting told PhysOrg.com. “Describing the motion of a material particle is a key concept in classical physics. Demonstrating non-classical features in the motion of a material particle thus reveals best the incompatibility of our experienced world with a classical description.”

Gneiting and Hornberger predict that, although their scheme faces technological challenges, experimentally realizing their method seems to be within reach of present-day technology. They have published their proposed method in a recent issue of Physical Review Letters.

To realize the entanglement of moving material particles, the physicists proposed using a Bose-Einstein condensate (BEC), which is an ultra-cold state of matter that displays collective quantum properties even for a large number of particles. When made of lithium molecules, a BEC has the advantage of possessing a relatively long lifetime of 10 seconds, which would enable researchers to apply a macroscopic time separation of one second between pulses which split the molecules.

By applying two field pulses at the BEC molecule, it’s possible to separate, or dissociate, the molecule into two atoms traveling in opposite directions from the source. Each counterpropagating atom has two wave packets corresponding to the two possible dissociation times: an early and a late wave packet. Then, simple position measurements behind interferometers reveal the correlations between the early and late wave packets of the two atoms. Their entanglement is verified if these correlations violate a Bell inequality.

As Gneiting and Hornberger explain, the Bell measurement is analogous to detecting the spin rotation of a particle. In this view, the early wave packet could correspond to spin up, and the late wave packet to spin down.

“The interferometers reveal the entanglement between the two atoms by reuniting the early and the late wave packets on each side,” Hornberger explained. “The resulting interference influences at what direction the atoms exit the interferometers, which can be detected by simple position measurements. The latter can be easily understood from a classical point of view, which permits to compare the experiment with the classical expectation.”

One challenge in performing an experiment of this motion entanglement will be to control unavoidable wave packet dispersion. If the early and late wave packets broaden too much, their distortion prevents accurate measurements. But if researchers can successfully perform the experiment, the results may provide insight into how accurately the macroscopic world can be described by local realism.

“In general, violation of a Bell inequality demonstrates the incompatibility of a realistic and a local description of our physical world,” Gneiting said. “Establishing such a violation even in the motion of material particles and on everyday life scales makes it ever harder to come up with a plausible alternative theory based on hidden variables, even when dispensing with the combination of reality and locality.”

More information: Gneiting, Clemens and Hornberger, Klaus. “Bell Test for the Free Motion of Material Particles.” Physical Review Letters 101 260503 (2008).

Copyright 2008 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

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Noumenon
4.6 / 5 (49) Jan 16, 2009
Interesting to say the least. Unfortunately, forcing Reality into conceptual forms in which our minds happen to have been equipped with, isn't going to provide essential understanding. We can know about the leash but not the big invisable dog.
Modernmystic
2.4 / 5 (9) Jan 16, 2009
I'm still of the opinion that all the contradictions that currently exist between the quantum world and the classical world will disappear when our conceptual model/theory undergoes another fundameental and radical upgrade...much like relativity.

I think all those contradictions are merely a result of our poor understanding....rather than a fundamental inability to understand.
Noumenon
4.6 / 5 (48) Jan 16, 2009
I hope so, mainly because that would be startling. Phenomenal reality includes as a component the observer, and is therefore a delimited reality. Some say that IS the entire reality,... but why would that happen to be the case, that noumenal reality, all of reality could be encapsulated within a limited functioning blob.
superhuman
3 / 5 (4) Jan 16, 2009
The contradictions will all go away once the new theory is here. Most of quantum mechanics will be reinterpreted in terms of deeper underlying theory, and all the mystifying nonsense will be gone.
Einstein was right, Nature does not play dice.
johanfprins
1.9 / 5 (7) Jan 17, 2009
The "contradictions" are all caused by the Copenhagen fairytale interpretation. Maybe one should call it the Hans Christian Anderson "worldview". The fact is that Schroedinger has solved quantum mechanics completely but allowed himself to be bamboozled by Bohr, Born and Heisenberg; who advocated the principle of complementarity by assuming that REAL particles and waves are complementary: There are no REAL particles; only waves with quantized energies which are determined by the boundary conditions under which they find themselves. Once applying this concept all the "contradictions" and funny behaviour, like, for example, entanglement and the Aharanov-Bohm interaction can be modelled by using realistic physics-equations.
superhuman
2.3 / 5 (3) Jan 17, 2009
Yeah, although I don't know historical details I certainly agree that particles are not real.
Particles are useful as an approximation in the macro world but nothing more. The waves are very real, there are only waves, and not probability waves, field waves.
Tachyon8491
1 / 5 (2) Jan 17, 2009
In the context of wave-particle duality and its paradox we should not forget the even more fundamental attribute of any ontological action-process or object-process (see Searle; Dennett) namely their intrinsic and inseparable intentionality. Any propagation of information, composed of an attributional constellation as an intentionality-modulated complex of inter-species languages (a meson, virus, an atom and a kangaroo are all species in the cosmic continuum of organicity if we don't scholastically divide the ontological universe into "living" and "non-living" domains) characterises its source. What you hang on your walls characterises you as much as the informationality-modulated wave-complex emitted by a macro-particle composed of more fundamental and primary, resonant quantum components. Finally, all is an expression of consciousness in the pursuit of progressive evolutionary quality (Pirsig)

FV
johanfprins
2 / 5 (4) Jan 17, 2009
Wow Tachyon8491,

This is surely NOT intended to be physics; is it??
superhuman
1 / 5 (1) Jan 17, 2009
In the context of wave-particle duality and its paradox we should not forget the even more fundamental attribute of any ontological action-process or object-process (see Searle; Dennett) namely their intrinsic and inseparable intentionality. Any propagation of information, composed of an attributional constellation as an intentionality-modulated complex of inter-species languages (a meson, virus, an atom and a kangaroo are all species in the cosmic continuum of organicity if we don't scholastically divide the ontological universe into "living" and "non-living" domains) characterises its source. What you hang on your walls characterises you as much as the informationality-modulated wave-complex emitted by a macro-particle composed of more fundamental and primary, resonant quantum components. Finally, all is an expression of consciousness in the pursuit of progressive evolutionary quality (Pirsig)


Intentionality is not a scientific concept but a philosophical one, philosophy as such is not falsifiable and everyone is free to think what they want but arguing about it makes as much sense as arguing about faith.

Yes, information often characterizes it's source to some extent, but comparing humans to physical entities such as waves or particles doesn't make much sense from scientific pov, and there is no such thing as "informationality-modulated wave-complex" there is complex wave function otoh.

"All is an expression of consciousness in the pursuit of progressive evolutionary quality" this is a clear example of statement of faith as "all" is not available to us to test and therefore we can't say what "All" is. Besides in the part of "all" to which we have access evolution is present only in a tiny fraction. In fact evolution and life require local decrease in entropy while in the vast majority of observable universe entropy is increasing, therefore we can say that actually most of accessible "all" is an expression of anti-evolution. As for consciousness its not even properly defined so any attempt to make definite statements about it is futile.
Pointedly
1 / 5 (1) Jan 17, 2009
Superhuman, I agree largely with what you have to say in your previous comment. I think, too, there is something to be gained from relating some aspects of this discussion to work being done by Stephen Wolfram. Not only does his work provide some unique and interesting insights, it raises many new and interesting questions. I mention his work here because, for many (if not most) scientists, Wolfram's work will not come to mind when discussing such matters. I think it adds an important--albeit very different--perspective.
KBK
1 / 5 (2) Jan 17, 2009
The logical summation is that science itself is not equipped with the tactic, points, background, or systematic type of logic required to puzzle out such things.

If science attempts, then it fails, for science, as a system, a methodology, is stated as being a 'hyper real' and 'repeatable' system of 'fact' and 'stability' whereas the nature of the universe is >>fundamentally NOT of that nature.

And science finds itself well out of it's league--and hoists itself via it's own ass.
Alexa
1 / 5 (4) Jan 17, 2009
It's not true, the spin is only microscopic quantity. Even the surface of macroscopic droplet is covered by tiny vortices, which are responsible for mass/energy density gradient of it.

The splitting of probability waves by magnetic pulse corresponds the spliting of undulating oil droplets inside of lava lamp by thin wire. The separated droplets will remain undulate at phase and after occasional reconnection they will restore the surface undulations of original droplets. They're not required to communicate at distance, because they have a "memory".

http://www.google...ch?q=AWT entanglement
Alizee
Jan 17, 2009
This comment has been removed by a moderator.
out7x
1 / 5 (1) Jan 29, 2009
Velocity is not a quantum property. This article is nonsense.