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A Astronomical Implications of Quantum Entanglement?

  1. Apr 1, 2016 #1
    Astronomers often use the speed of a QRB or other phenomena to put a maximum bound on the size of the generating object. I find the most recent of many examples in "Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak", Gandhi et al 14 Mar 2016, http://arxiv.org/abs/1603.04461. Lead author of the study Dr Poshak Gandhi comments: “The very high speed tells us that the region where this red light is being emitted must be very compact." Of course the way this works is, signals can't travel FTL. So since a flare was as short as 24 milliseconds it had to come from a source less than about 7200 km; in this case it's a jet from the central object, which they further estimate (by putting the flare at a few hundred gravitational radii) at something like 20 km diameter.

    This idea is of course ubiquitous. It has been used to upper-bound the size of quasars, and so forth. It's also related to the cosmological horizon problem. The early universe's particle horizons were not large enough to allow uniform CMBR, because it would have required FTL "communication" to reach thermodynamic equilibrium back then. Of course inflation is the favored explanation today.

    Now, quantum entanglement results in non-local effects, which is a bit like FTL communication, when the wave function of entangled particles collapses due to measurement. Of course this can't be used for communication, since only random values of the entangled properties are "communicated" in this way. To put it like a first-grade reader, Alice can't force her particle to be spin up, so that Bob can read that as a binary "1". She can only force it to be up or down randomly. She knows Bob will read the same value, up or down, but can't control which it will be.

    You may not know that multiple entangled particles are commonly demonstrated. A couple papers are "Experimental demonstration of a hyper-entangled ten-qubit Schrödinger cat state", Gao, Lu, Yao, Xu et al 2010, http://www.nature.com/nphys/journal/v6/n5/abs/nphys1603.html; and "Multipartite Entanglement Among Single Spins in Diamond" Neumann et al 2008, http://science.sciencemag.org/content/320/5881/1326.abstract. Also check out biphoton frequency combs.

    Putting these facts together it appears that entanglement could allow much larger objects to produce the fast flares usually ascribed to BHs, to account for the horizon problem, and so forth. It's not necessary for Alice to communicate a selected state to Bob - just any random state, like a temperature of 2.94K.

    Suppose Alice is at one end of an object much larger than 7200 km; say, a light-hour or so. Bob is at the other end, with Eve, Colin, Dick and Jane, and 10^20 more friends interspersed throughout. They all have entangled particles which are, somehow, suppressing flaring. Now, Alice (a natural phenomenon of some sort, you understand) observes, or measures, her particle. Suppose its wave function collapses into the |allow_flaring> state. Then all the entangled particles do so, and we get simultaneous flaring throughout. When astronomers on Earth see it, 7800 years later, it lasts only 24 ms so they incorrectly conclude it came from a very small object.

    Since this idea questions many well-accepted astronomical conclusions there must be something wrong with it. What is it?
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Apr 1, 2016 #2
    Could you physically describe in detail the object in your thought experiment as well as where Alice and her friends are in relation to it?

    Also, keep in mind that you're describing 2 different sets of observers: Alice and her friends, and also the astronomers on earth. As far as I know all experiments that utilize the collapsing wavefunction model only have 1 observer.
     
  4. Apr 1, 2016 #3
    Well, NC_Seattle, no I can't. The general idea is that with entangled particles a random wave collapse could implement a simultaneous change of state over an arbitrarily large area - invalidating the assumption that a change can propagate only at the speed of light. There are so many examples of that assumption in the literature I decided (instead of picking one at random), to grab the latest one I could find for my gedanken. Turned out to be Cygnus V404, published just 2 weeks ago. But I don't know GRB's well and can't give details.

    Perhaps I should have gone with quasars. In that case the center of a distant galaxy is varying so quickly that under current assumptions it "must" be caused by a BH. Instead it could be an entire galactic bulge doing it. Or Higgs spontaneous symmetry breaking mechanism. My idea could explain why we see no domains with different particle masses caused by Higgs boson interaction. One imagines that, when the temperature drops to 10^16K, the original vector boson plane rotates simultaneously everywhere by the same random Weinberg mixing angle to produce the W's, Z and photon, with the observed masses. Therefore no domain walls - because all the vector bosons were entangled.

    But, actually, I don't know those areas all that well either ... so bottom line, I can't describe a convincing gedanken. I'm sure someone else can do so, however, and await their input with interest. One question is - how did all those particles get entangled? And, what causes the collapse? And, in the case of GRBs and quasars, we need a continual supply of entangled particles to cause such bursts as time goes on. I leave these details for others to work out :-)

    In this case the one observer is Alice. The astronomers are not collapsing anything, just seeing the long-ago results. Note, in a typical gedanken Bob can also be considered the collapser; the order (in time) they read their particle's spin doesn't matter, they get the same random result regardless. Also worth noting, I'm well aware that the word "simultaneous" is supposed valid only for local contact transformations. The use of the word is deliberate: entanglement strikes at the heart of that supposition.
     
    Last edited: Apr 1, 2016
  5. Apr 2, 2016 #4
    Having thought about it, it's not as easy as it looks.

    Entanglement's just another word for "sharing a (partial) wave function" (I think). If you want a lot of entangled particles, the obvious way is a Bose-Einstein Condensate (BEC). And fermions can partipate in a BEC by first pairing them to get a boson, as in Cooper pairs. Of course in practice this is hard to create, even harder to preserve the entanglement, as shown in Quantum Computing, but let's not worry about that.

    Now one needs a source of such particles. Suppose the initial Big Bang, or a quasar, etc consists of or produces a BEC. But in the case of Big Bang this is exactly the sort of assumption inflation was designed to avoid: that the universe started off with very low entropy. So the fact that a uniform Big Bang solves horizon problem is no big deal - we already knew that, even without entanglement. It could also be used to replace spontaneous symmetry breaking, but so what? We already have Higgs mechanism, experimentally supported; and it accomplishes other objectives too (Goldstone bosons etc). So again, entanglement is not helpful.

    For fast-fluctuating GRB's it's very unlikely a quasar, for instance, produces BECs, or that coherence can remain in the extreme conditions found there, especially when the bosons are separated. (In which case the BEC becomes only a "partial BEC" because position no longer indistinguishable). But (in for a penny in for a pound) suppose we do assume all that, which allows us to get Alice, Bob and friends positioned anywhere we want, even on separate objects throughout a galaxy. Even so it's hard to see what good it is.

    Regarding simultaneity, the problem is, there's no way (I think) for a BEC or any shared wave to incorporate time information. Thus if a boson in a BEC decays, the others don't. Instead it would just destroy the entanglement. Nor is there any other way to get timing info (right?). So if you somehow separate them, without decohering, they still can't be used for coordination. For that you need even more assumptions. For instance, that they are in contact with a set of observers comoving with CMBR, and get time ticks from them. Basically they have to be little robots with impressive capabilities. That's bad, but the real problem is: with such assumptions you wind up not needing entanglement at all (to help them co-ordinate flaring)!

    The other problem is: to get entanglement to mediate any real effect. How can entangled particles "suppress flaring" then allow it? It seems that to do anything they have to be "measured". For instance we might imagine they are like LCDs. When polarized one way they block EM radiation (flare), the other way they let it through. But being polarized and blocking EM, is like a measurement. If a (previously) entangled particle does that I believe the wave has now collapsed to |block flare>. You can no longer switch to |allow flare>. As long as the particles don't do anything entanglement can be preserved, but not after.

    So, without so many assumptions that the entanglement aspect becomes redundant - entanglement is useless! Apparently. Since I got no answer to "what's wrong with this idea?" I assumed it was alright - but surely what I've said above must be well known ... ? Not that I'm asking - seems no point in doing so.
     
  6. Apr 2, 2016 #5

    Ken G

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    I think the problem is that the idea that the timescale of variation limits the size of the source is never intended as an inviolate law of physics (though you are right, it is sometimes cast that way). It simply reflects an assumption about the nature of the mechanism. It is actually easy to come up with mechanisms that violate this rule, without invoking anything as exotic as entangement. For example, we have the phenomenon of "light echoes", where a supernova occurs and "lights up" circumstellar material. Hundreds of years after the supernova you can see material being lit up that is hundreds of light years apart, and that material can light up on the same day if there is the same total path length of light from the supernova to the material and then to us. So if you don't know the mechanism that causes this, you see what looks like a flare in gas that is separated by many light years, yet it all lights up the same day. So it's not a law of physics, it requires additional assumptions about the mechanism that is producing the flare. A "generic" mechanism (unlike a light echo) is usually not able to do that, so that's what is being invoked in that reasoning.
     
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