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Can entangled photons be used to explore black holes?

  1. Mar 8, 2017 #1
    Gabriela Lemos and her team successfully entangled photons. Would it be possible to explore the interior of a black hole by letting one of the entangled photons enter beyond the event horizon and observe the impact on the other?
  2. jcsd
  3. Mar 8, 2017 #2


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    No. Information cannot be transmitted via entanglement. There are hundreds of threads here on PF about that fact. I suggest a forum search.
  4. Mar 8, 2017 #3
    Is there a link that could help me understand why?
  5. Mar 8, 2017 #4


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    There are hundreds of threads here on PF about that fact. I suggest a forum search.
  6. Mar 8, 2017 #5
    I'm new to the site. Thanks for your guidance.
  7. Mar 8, 2017 #6


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    I think I understand the original question better now. Here is a related reference:


    Entangled photons are used for imaging. There is no FTL communication (or similar) in this interesting variation.

    Cindy: In this experiment, the imaging technique relies on a trick whereby one of the photons is of such wavelength that it passes through the object being scanned. That wouldn't work with a black hole, obviously the light would be trapped in the black hole.
  8. Mar 8, 2017 #7
    As mentioned, entanglement does not transfer information. Suppose photon B falls into the black hole and photon A is for keeps. Then measuring photon A (or a whole series of "photons-A") yield random results. You need photon B to observe any kind of correlation, let alone "impact". And photon B has been eaten.
  9. Mar 8, 2017 #8
    What about:
    1- Entangle A with B
    2- Entangle B with C
    3- Send B to the Blackhole.
    4- Measure A and C

    If measurment shows correlation between A & C then we have info about B still not destroyed. So we got info from inside the black hole!

    But that is impossible! what went wrong here?
  10. Mar 8, 2017 #9


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    You haven't explained how you are going to perform this sequence of entanglements. When you do, you will find that either A and C have been entangled or they haven't. If they are, then measurements on them will be correlated no matter what happens to B; conversely if they aren't then measurements on them will not be correlated no matter what happens to B.
  11. Mar 8, 2017 #10


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    This experiment is no different from simply throwing B away. Nothing that happens to B will observably affect A or C. Adding a third qubit doesn't make the no-communication theorem suddenly not apply. (Also, you should know that entanglement is monogamous. B can't be fully entangled with both A and C. But okay, assume you're talking about a weaker entangled state.)

    The way you actually use entanglement to study a black hole is you make an EPR pair AB, send B into the black hole, wait a bajillion years for the black hole to evaporate, do a gazillion steps of lucky uncomputation to remove all the stuff that got mixed into B, then do some relevant two-qubit measurement on A-vs-B.
  12. Mar 8, 2017 #11


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    You may not be familiar with Entanglement Monogamy. If B & C are maximally entangled, then A & B cannot also be maximally entangled. Monogamy = Only one maximally entangled partner allowed at a time. :smile:

    A, B and C can be less than maximally entangled. Of course you still cannot obtain information from that black hole if your "probe" doesn't return.
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