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Can a Photon be thought of as a bit?

  1. May 5, 2013 #1
    A photon is emitted and then absorbed. And since a photon travels at the speed of light, time does not exist. So that should mean that a photon is in either a state of emission or a state of absorption.

    Doesn't that make a photon a type of bit?

    Furthermore - if there is no time involved then would it be correct to say that a photon ican be in both states (Emission and Absorption) at the same time? Wouldn't it also make a photon a Qbit?
  2. jcsd
  3. May 5, 2013 #2


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    Absolutely not. A photon has wavelength and that can't be represented as a binary quantity.
  4. May 5, 2013 #3


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    Emission and absorption are not quantum states.

    You should also not attempt to transform to the photon frame to arrive at the conclusion that a photon has "no time involved".

  5. May 5, 2013 #4
    If you recall intrinsic properties of photons, such as charge, mass and spin, ARE observables...as with matter particles......so that is an indicator 'time does not exist' is an oversimplification .....Somebody even said 'Eternity is not time at all for a photon.' Better to say time is not defined.

    Well, no, but the presence of a photon IS different than the absence or a photon....so THAT information is encoded as with all particles.

    nice try but alas, as you can probably tell, no....that would be too easy....

    I kept a mathematical explanation of 'time does not exist for a photon' posted in these forums, but alas I cannot find it....I will look tomorrow...was from PeterDonis, I believe.
  6. May 5, 2013 #5


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    For a photon, time does not exist? Tell that to the photon that took 8 minutes traveling at the speed of light from the sun to get here. Tell that to the photon that was emitted in the Big Bang and is just now being absorbed 13.8 billion years later. :biggrin:
  7. May 5, 2013 #6
    Relatively- would it seem like 8 minutes or 13.8 billion years to the photon?
  8. May 5, 2013 #7


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    What things might "seem like" to a photon is meaningless. A photon does not carry a pocket watch.

    The quantity called proper time can be defined for particles - it's the time that elapses between two events in the particle's rest frame. But a photon does not have a rest frame, and proper time for a photon can't be defined.

    What does have meaning is the coordinate time in some inertial frame. Yes, it's relative. :uhh: But the elapsed coordinate time between the photon's emission and absorption is what serves to separate the two events.
  9. May 5, 2013 #8
    Related to Bill_k's comment:
    is this, from a prior discussion alluding to spacetime diagrams:

    or equivalently,
    says Roger Penrose in THE ROAD TO REALITY

    Yes, here is the quote I referred to above which I like:
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