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    Quantum Entanglement: A Third Entangled Particle?
    By News Staff | December 17th 2012 03:01 AM | 9 comments | Print | E-mail | Track Comments

    Quantum entanglement is a central principle of quantum physics - the science of sub-atomic particles. Multiple particles, such as photons, are connected with each other even when they are very far apart and what happens to one particle can have an effect on the other one at the same moment, even though these effects cannot be used to send information faster than light.

    In 1935, Albert Einstein, Boris Podolsky, and Nathan Rosen, referred to in the shorthand form EPR today, published a thought experiment designed to show that quantum mechanics, by itself, is not sufficient to describe reality. 

    Using two entangled particles they tried to demonstrate that there must be some hidden parameters that quantum mechanics does not account for. Later, John Bell and others showed that the kind of hidden parameters  Einstein, Podolsky and Rosen had in mind are incompatible with our observations.

    The mystery at the heart of quantum mechanics thus remains intact. But the entanglement first proposed by the EPR trio is now a valuable resource in emerging quantum technologies like quantum computing, quantum cryptography, and quantum precision measurements. Physicists have published a new paper which they say builds on the original ideas of Einstein and adds a new one: a third entangled particle.

    The new form of three-particle entanglement demonstrated in their experiment, which is based on the position and momentum properties of photons, could lead to new fundamental tests of quantum theory that deepen our understanding of the world around us. 

    "This work opens up a rich area of exploration that combines fundamental questions in quantum mechanics and quantum technologies," says Christoph Simon, paper co-author and researcher at the University of Calgary.

    "It is exciting, after all this time, to be able to finally create, control, and entangle, quantum particles in this new way. Using these new states of light it may be possible to interact with and entangle distant quantum computer memories based on exotic atomic gases, " says Thomas Jennewein, whose group at the University of Waterloo carried out the experiment.

    The next step for the researchers is to try to combine the position and momentum entanglement between their three photons with more traditional types of entanglement based on angular momentum. This will allow the creation of hybrid quantum systems that combine multiple unique properties of light at the same time.

    Published in Nature Physics




    Comments

    fundamentally
    If you accept that quantum state functions are 1+3D quaternionic probability amplitude functions (QPAD's) and that our common complex wave functions are 1+1D abstractions of these QPAD's, then the fact that QPAD's are combinations of a scalar field and a 3D vector field quickly lead to the main functionality of the quantum state function. It must keep things together. This is put into words in Bertrand's theorem. The fields diminish their strength as 1/r. It also means that they exist and are non-zero all over universe
    It also means that all these fields overlap. Since they are built of the same stuff (probability amplitude distributions) they will superpose. In fact universe is covered by one big QPAD that here and there shows an excitation that we call particle.
    We have a very mysterious name for the overlap. We call it entanglement.

    (For a more detailed vision on QPAD’s, see http://www.scitech.nl/English/Science/OnTheHierarchyOfObjects.pdf)

    If you think, think twice
    It also means that they exist and are non-zero all over universe.
    We have a very mysterious name for the overlap. We call it entanglement.
    Mysterious for the very good reason that to explain the correlations in terms of cause and effect you have no option but to postulate faster than light causality. Constant exposure to talk about "spooky action at a distance" may inure us to the wierdness of it, but a collection of particles which acts as a single quantum object regardless of distance - oblivious of any 1/r law - is mysterious any way you look at it.  
    fundamentally
    It all comes down to what the identity of a particle is. Is it its "wave function"? or its confined to the region where the fields that constitute the particle couple. What if the wave function and its coupling partner are modes of the same oscillation? 
    The above reference gives an indication in that direction. 
    If you think, think twice
    I'm more than a little rusty on these matters, but I had an idea this is already the way particle creation is handled in QM? :)
    fundamentally
    It not only occurs during the creation of the particle. It happens througout its life. But after the creation both fields have 'captured' each other.

    The paper about the hierarchy of objects explains all fundamental 'laws' that are encountered in the discussed hierarchy which ranges from propositions about physical objects until elementary particles.
    Amongst them are the cosmological principle, the existence of quantum physics, the existence of a maximum speed of information transfer, the existence of physical fields, the origin of curvature, the existence of elementary particles and the existence of generations of elementary particles.
    If you think, think twice
    If three photons can be (or are found to be) entangled then why not four, five, n, or indeed all photons? Since presumably all elementary particles were present in the singularity preceding the rupture of the Big Bang, perhaps the entanglement of all with all was then actually the norm - a property that can now be re-established and utilized.

    Eric that is correct what you are saying - everything is entangled with everything else

    I'm sure a lot have already perused, but some of you all find this Gerard 't Hooft (version 3) paper interesting.

    http://arxiv.org/abs/1112.1811v3

    I like 't Hooft, and contrary to what some believe, he shows one can work on the "fringe" of a field. yet over time be recognized. He's still not afraid to step into a discussion with some pretty "radical" ideas.

    Bonny Bonobo alias Brat
    "This work opens up a rich area of exploration that combines fundamental questions in quantum mechanics and quantum technologies," says Christoph Simon, paper co-author and researcher at the University of Calgary.
    "It is exciting, after all this time, to be able to finally create, control, and entangle, quantum particles in this new way. Using these new states of light it may be possible to interact with and entangle distant quantum computer memories based on exotic atomic gases, " says Thomas Jennewein, whose group at the University of Waterloo carried out the experiment.
    Why  publish all of this information about this very interesting article and not provide a link to it?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at http://www.science20.com/forums/medicine