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Entanglement and the Mach principle

  1. Sep 17, 2005 #1
    Has anyone read something related? Thanks to point me to such papers, and to express your ideas or knowledge.

    The Mach principle aknowledges that a "frame of inertia" can only be conceived with respect to the whole bulk of nearby universe. That is to say that physics frame of reference is defined by matter interacting on a large scale through gravity. This is -of course- fully integrated in GR. I ask myself if quantum entanglement could not be limited by these very weak, long-range, but nevertheless determining interaction.
     
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  3. Sep 17, 2005 #2

    ZapperZ

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    I'm not sure exactly what you are asking here, but if you are trying to ask whether the degree of entanglement is limited in an accelerated, non-inertial frame, then that is still a very active research area (with not a whole lot of experimental results yet). A new paper published this week in PRL has the latest of such theoretical development. A version can be found on the eprint arxiv:

    http://www.arxiv.org/abs/quant-ph/0410172

    Zz.
     
  4. Sep 17, 2005 #3
    entanglement is a space-related phenomenon

    As I understand it, the fascination for entanglement when one tries to understand the quantum, is that -in a sense- it highlights some kind of break of the barrier of space. But it doesn't contradict relativity. It challenges our understanding.

    Since space is the central point of GR, the theory for gravity, I was asking myself about the relations between gravitation and entanglement. I mentioned the Mach principle because it recalls me that space exists (measurable) because there are interactions on a large scale through gravitions. Therefore the link I imagined.

    I also asked myself if gravitation -after all- could be a manifestation of a sort of large-scale entanglement. This is an idea still closer to the Mach principle. It would make entanglement not an understanding problem for QT but an explanation in GR, or the reason for space.

    Did you cross any tought about that ?

    By the way, the paper you mentioned looks stimulating. I will read it. Thanks.

    Michel
     
  5. Sep 17, 2005 #4

    DrChinese

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    Are you asking: If there is quantum gravity, would an interaction (read: observation) with a graviton end the entangled state? I mean, after all, if there is quantum gravity then we should be living in a bath of gravitions. So assuming that is the question at hand...

    1. That logic would also apply to other quantum phenomenon. For example, the double slit experiment.

    2. I have wondered for a long time if the existence of entanglement, double slit, etc. was not a counter-example to demonstrate that there is no quantum gravity. I don't think so any more, because it is actually possible to have all kinds of interactions that do not affect mixed quantum states. I.e. if there is a superposition of states, interactions with the overall field won't change the outcome unless we gain information from it. I think... :smile:

    On the other hand, ZapperZ's timely reference shows that entanglement would degrade in accelerated reference frames under GR. In the limit in which the observers are in the same inertial frame, there is no degradation effect.
     
  6. Sep 18, 2005 #5
    What does "some kind of break of the barrier of space" mean?

    Space is measurable because distance and time are defined and there
    are interactions on a large scale via electromagnetic waves.
    Or am I missing something here?

    Gravitational systems are, in a sense, entangled. But I'm not
    sure if they meet the technical criteria for entangled systems
    as defined via quantum theory.
     
    Last edited: Sep 18, 2005
  7. Sep 18, 2005 #6
    Sherlock,

    Honestly, I did not mean something very precise. I had in mind that two particles separated by 1 billion light-years could be entangled. Even if this relation doesn't give a mean to transmit information instantaneously over this distance, it remains a surprising and amazing fact. Specially because it is more that a simple statistical correlation, as I understood.

    My question is related to my questions about space ... Is space not a manifestation of interactions instead of a frame for them?
     
  8. Sep 18, 2005 #7

    ZapperZ

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    You need to cite sources of your "understanding", because it is certainly not part of the standard definitions of the terms you are using. Please include "entanglement" in your definitions.

    Zz.
     
  9. Sep 18, 2005 #8
    ZapperZ,

    I you throw billions light-years apart a white and a black object. Since you are aware of the initial fact, detecting on one side a white object you immediately know that on the other side an observer will see the black object.

    This is not the nature of entanglement. The evolution of the couple of objects (like spins) proceeds as a whole. This not like the black or white objects above who are linked only by an initial condition.

    What is then the meaning of the distance between two entangled particles? There is a distance, of course, since the measuring devices will be far away from each other. The system of both particles interacts with the world via two positions in space instead of one. But the particles are in a sense very close to each other. Only the un-tangled measuring devices are 'separated'.

    If the universe contained a large amount of entangled particles (if not a majority, because of the big bang) would that not have an effect on the interactions and on the properties of space-time?

    I am looking for ideas and papers related to the impact of entanglement on 'gravity' or 'space'. I am also interrested in more extreme points of view ... but possibly with a good basis.
     
  10. Sep 18, 2005 #9

    ZapperZ

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    Then you are using the same words, such as entanglement, but with different meanings. Your idea of what is entanglement has nothing to do with QM entanglement, and NOTE that you posted this in the QM section of PF. So you should be aware why this is creating utter confusion.

    Entanglement has nothing to do with what you just described as an example. I strongly suggest, before you use a term you are not familiar with, that you first figure out the exact definition. If not, you will continue to be met with this type of response when you try to ask such questions to people who work in this field.

    Zz.
     
  11. Sep 18, 2005 #10
    ZapperZ,

    I am very sorry for the confusion. Indeed, I explained what entanglement is not.

    It is true that explaining what it is, is -I feel- much less interresting. It all amounts to the fact that a two-particle system is described by an unseparable wave function. The consequences are more colour-full and -as you kwow- raised heated discussions. However, in these discussions proving what entanglement is not was very useful, specially the Bell theorem.

    My current interrest (non professional) is investigating the role entanglement might have on GR and if entanglement would not reveal something about the nature of space-time that was not considered yet. Being unable to develop the topic by myself I am asking for hints and maps.

    Googling ("scholarly papers beta") led me till now to a lot of papers but few I want to read and some I don't want to pay.

    By the way, my first references on this subjects are:

    - Quantum theory and measurement by JA Wheeler and WH Zurek, which collects all the historical paper related to this topic
    - Speakable and Unspeakable in Quantum Mechanics by JS Bell
    - papers on Bohm point of view

    I also read many papers by A Aspect as well as a DVD conference by him:

    Les tests et effets de la physique quantique
     
    Last edited: Sep 18, 2005
  12. Sep 20, 2005 #11
    For two separated particles to be entangled they have
    to have something in common, and that something has to
    be analyzed by a common instrumental variable.

    Now, before you say that Bell tests have shown that this
    can't be, consider how entanglement is experimentally
    produced. Either the entangled particles have been emitted
    by the same oscillator at the same instant, or they have
    interacted, or they have been in some way altered by
    some common mechanism.

    So, it's not really so mysterious that they should have
    *something* (even if we can't say exactly, qualitatively
    what it is) in common.

    I would say it's both. Space in the physical world is the manifestation
    of interactions. Coordinate systems in the models that we make
    of the physical world are frames in which physical interactions
    can be quantified.
     
  13. Sep 20, 2005 #12
    I think of gravitation as a manifestation of complex wave
    system interactions on a level that isn't directly amenable to our
    sensory perception. Wave mechanics at a sub-microscopic
    level -- GR, and associated geometric model of 'bent space' or
    'curved space' being a simplistic approximation of it.

    Entanglement is just one aspect of the whole wave picture
    and is narrowly defined in quantum theory.

    One might think of gravitational systems (solar
    systems, local star groups, galaxies, galaxy groups, etc.)
    as being entangled ... I think.

    But, this still wouldn't give you the how and why of it.
    For that you'd need a detailed model of the interactions.

    Gravitons is a start.
     
  14. Sep 20, 2005 #13
    And what if space was a global measure of entanglement ?

    Sorry for the loose speaking.

    But in the end this message title is what I wanted to say and ask.
    I understood the Mach principle as a way of saying: interactions defines where each object lies.
    I ask myself now: what about entanglement? Entanglement between two extremely prepared laboratory particles is an exceptional situation that may exagerate our view on entanglement. Maybe entanglement is so common that we forget about it: could not space be a manifestation of entanglement, a result of the unseparability on the scale of the universe?
     
  15. Sep 20, 2005 #14
    On the scale of the universe, everything in it
    would be entangled wrt the general movement
    of the universe. For example, if the universe is
    rotating, then everything in the universe is
    entangled wrt that rotation. If the universe is
    expanding, then everything in the universe
    is entangled wrt that expansion. At least,
    that's how I'm initially thinking about it.
    Maybe you mean something different?

    I think you should post your question in the
    cosmology forum. Or maybe the new/speculative
    theory forum (I think there's something like that).
    The consideration seems interesting -- but I don't
    really understand yet what you're getting at.
    I don't know if I would think of space as a
    "manifestation of entanglement". Entanglement,
    as I understand it, has to do with motional
    contexts (scales) in which the behavior of two
    or more objects can be correlated. If one asks whether
    some objects are entangled, then one is in effect
    asking what they have in common. So, I guess
    I'd say (until I understand better) that entanglement
    is a manifestation of space, in the sense that
    observation of entanglement depends on the
    scale (context) of the observation.

    It's certainly possible that a general definition
    for "entanglement" in nature might eventually be
    developed -- entailing some sort of qualitative
    understanding of it. The qm definition/criteria
    for entanglement doesn't really provide a qualitative
    understanding of what entanglement is in nature,
    afaik.

    I've haven't thought much about Mach's principle.
    I would bet that there has been a lot of discussion
    of this in the cosmology and also relativity forums,
    and that there are regular posters there who have
    considered things closely related to your issue.
     
  16. Sep 21, 2005 #15

    DrChinese

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    1. The usual definition of entanglement is that particles share a quantum state function. For your question to make sense, there needs to be a connection between gravity and quantum theory that is currently unknown. And there needs to be a manifestation of that connection as well. No one knows of any currently, so it ends up being pure speculation. I.e. could there be a connection we don't know about which explains a phenomenon we don't know about? Sure!

    2. It is certainly possible, on the quantum side, that entanglement is more common that we know. After all, any time we don't know the state of a set of particles, there is the potential that there are entanglement effects that we can't see at this time. Although this too is pure speculation, I would not be surprised if new (and relatively more common) quantum entanglement methodologies were found some day.
     
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