Can entangled photons be used to explore black holes?

  • Thread starter Cindy Hops
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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?
 

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phinds
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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?
No. Information cannot be transmitted via entanglement. There are hundreds of threads here on PF about that fact. I suggest a forum search.
 
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Is there a link that could help me understand why?
 
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phinds
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Is there a link that could help me understand why?
There are hundreds of threads here on PF about that fact. I suggest a forum search.
 
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I'm new to the site. Thanks for your guidance.
 
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DrChinese
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I think I understand the original question better now. Here is a related reference:

http://www.nature.com/news/entangled-photons-make-a-picture-from-a-paradox-1.15781

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.
 
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  • #7
entropy1
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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.
 
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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?
 
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But that is impossible! what went wrong here?
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.
 
  • #10
Strilanc
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What about:
1- Entangle A with B
2- Entangle B with C
3- Send B to the Blackhole.
4- Measure A and C
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.
 
  • #11
DrChinese
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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?
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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