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Uncertainty principle and information theory

  1. Feb 19, 2012 #1
    does the fact that there is a limit on how much can be observed on electrons location and momentum have anything to do with the finiteness and conservation of information?

    is the total momentum plus location of an electron unknown to us or is it also unknown to the universe?

    meaning, does an electron posess the information of both its location and momentum in the universe, and can that full information be propagated?
     
  2. jcsd
  3. Feb 19, 2012 #2

    Drakkith

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    The usual interpretation of the wavefunction is that a particle doesn't have a set momentum and position at the same time and isn't capable of having one.
     
  4. Feb 19, 2012 #3
    In simple terms (avoiding the concept of wave functions)...

    The finiteness of information is the same concept that there is a limit on how much can be observed on electrons location and momentum.

    The concept of conservation of information states that if there is a limit on how much is knowable about an electron's location and momentum then the same limit applies to how much can be observed on that information, so again it is roughly equivalent to the concept of the finiteness of information.

    The total momentum plus location of an electron is not only unknown, these quantities together do not have any meaning. In other words an electron which has a given momentum does not exist at any location, and vice versa.

    The non-existance of information about specific quantum states (as opposed to the mere unknowability of such information) was highlighted by the EPR (Einstein-Podolsky-Rosen) Paradox, and Alain Aspect's experiments confirming the 'resolution' of that paradox.
     
  5. Feb 19, 2012 #4
    damn this website is cool
    so the maximum amount of information an electron can propagate is im just guessing somewhere in between knowing an electrons momentum plus location and knowing only its momentum or only its location?

    also is this the basis for knowing what the smallest packet of information that can be propagated is?

    also, can a photon carry any information other than its wavelength etc, or can you tell from a photon where (where is probly the wrong word) the electron was when it emmited the photon?
     
  6. Feb 19, 2012 #5
    hi jadrian...I see one of your areas of personal interest is information theory, so I'll attempt to go a bit further here. I am NOT an expert, but am also interested. [and I see you just posted more interesting questions while I am typing this]


    First of all, I like Mr Anchovy's summary above, but am not sure how widely accepted all the the replys will be...If he could supply some links to sources that would help understand the context.

    Let's start with just what the Heisenberg uncertainty releation means, irrespective of 'information' was the subject of a painfully confusing, contradictory and lengthy discussion here: [I'm not at all sure all participants would agree with my summary but there sure were a lot of experts arguing/discussing.]

    https://www.physicsforums.com/showthread.php?t=516224

    My own summary notes from that thread:


    Next, here is an observation from DECODING THE UNIVERSE BY Charles Seife which I found to
    have very interesting explanations of 'information'. This book is for the general public, no math.

    This seems rather different than Mr Anchovy's post....but I have no idea if Seife's view
    is accurate or not.

    Also Seife, points out the quantum Zeno effect that if you keep rapidly 'measuring' a nucleus
    you can prevent it from decaying:
    :
    and when I checked it Wikipedia,

    http://en.wikipedia.org/wiki/Quantum_Zeno_effect

    you'll never guess the name that popped up with a neat quote: Alan Turing!!!!!!!

    I have often wondered about what isgoing on between information residing
    in quantum systems and their inherent superposition, just how multiple simultaneous quantum states are reflected in quibits which can take on those contradictory values.....

    Also, you might use the search function at the top of each page here for 'informaton' if
    interested and see what's been discussed previously .....I mention that because I spent well over a year on these fourms before I noticed it....
     
  7. Feb 19, 2012 #6
    jadrian: one caution...lots gets posted which is later refuted, people realize they did not post what they meant,etc,etc...so
    take replies with 'a grain of salt'....mine included!!

    You seem to have two issues here (a) what information exists, you use the term
    'propagates', and (b) what information can be extracted, what we can observe/measure.

    THIS should be interesting!!! I'm guessing: Get ready for some debates if the experts latch
    on to this discussion....one never knows if a discussion ends in 3 or 5 posts or goes on and on for weeks, even months!!!!

    This is one way to describe what happens:

    http://en.wikipedia.org/wiki/Observable_(quantum_computation)#Quantum_mechanics

    [I have yet to relate my limited communication engineering perceptions of information with
    those bubbling from quantum mechanics, but I can tell this description relates to my prior post about Heisenberg uncertainty: state preparation produces a statistical ensemble!!!.]
     
  8. Feb 19, 2012 #7

    jim hardy

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    I still think the doggone thing is someplace, just we cant measure it.
     
  9. Feb 19, 2012 #8
    my perception of information is something that is propagated or can be propagated. information that cant be propagated should not have any effect on the universe, therefore unpropagatable information could be regarded as having no existence correct?

    wow this **** is addicting
     
  10. Feb 19, 2012 #9
    yeah im with einstein on the dice thing. randomness and causality dont get along
     
  11. Feb 19, 2012 #10

    not that simple....for example, information beyond your timelike light cone has no effect on you, but affects all the universe within it's timelike lightcone.....How about encoded information which we cannot decipher??? [see below]

    Have you thought about information from the big bang...and that which 'disappears' into
    a black hole???

    I've collected some insights into information...none is complete but I found each to have an interesting perspective:

    an example:
     
  12. Feb 19, 2012 #11
    And yet the universe continues to function just fine....
    the problem is us, not nature!
     
  13. Feb 19, 2012 #12
    this is why i hold the belief that reality (information transfer) be defined/communicated at a point.
     
  14. Feb 19, 2012 #13
    randomness implies that events occur as if the events themselves had free will.
     
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