Even if neutrinos…

The possibility of faster-than-light phenomena is suddenly being taken very seriously. I am not in a position to judge that neutrino stuff — though, contrary to the Italian ministry of Education, I know that there is no tunnel 🙂

Suppose now that a new limiting speed v>c would be found. I want to stress that no signal at finite speed can explain quantum correlations arising from measurement of entangled states! How can one prove this? The final result has just been found; we are writing a paper, I shall link it when it comes out. If you are too curious to wait, you can get an idea from partial results: the first paper and some recent progress.

Bottom line: if the neutrinos are really faster than light, a lot of our knowledge of physics will have to be reconsidered; but it looks like the weirdness of quantum correlations and its implications will remain.

P.S. on 19/10/11: here is what I called above “the final result“.


About valerio

Principal investigator at Centre for Quantum Technologies and professor at National University of Singapore

Posted on September 28, 2011, in Latest topics. Bookmark the permalink. 4 Comments.

  1. Let’s face it: science becomes (even) more interesting when money is at stake.

    So I’m ready to bet 100 Swiss Francs with whoever desires that neutrinos are *not* going faster than light.

    If I’m right, I’ll welcome the money; if I’m wrong, it’s definitively worth the spending.

    (disclosure: stolen from xkcd/955)

  2. Hi Valerio,
    I don’t understand the link between your last paper (“the final result”) and your remark concerning the neutrino experiment.
    I didn’t read the paper in details, only the introduction and conclusion, but it seems to me that it has sense only if we believe in relativity : even in the abstract you write “assuming the impossibility of using quantum non-locality for superluminal communication”. You have to assume that light speed plays a special role in the story.
    Now when you write “even if neutrinos…”, for me it means “even if relativity was falsified”. I mean (beyond the fact that now we know the (trivial) cause of neutrinos’ delay 😉 that if we had experimentally proven that neutrinos were traveling faster than light, then superluminal communication wouldn’t be so chocking, wright?
    Maybe I missed something, I would be happy to know!
    Cheers, Loren

    • Hi Loren,
      Thanks for the comment 🙂
      The answer is: replace the speed of light by any other limiting speed for signals, let me call it C. As long as C is finite, you can define space-like separation. Then you can think of a Bell test in which the measurements are space-like separated in the new sense: if you want to explain quantum correlation with a hidden influence, this influence should travel faster than C. Our proof goes through without any modification: the hidden influence should either be instantaneous, or lead to observable signaling faster than C.
      Is it more clear? By the way, we had thought of writing a generic “signal speed” instead of “speed of light” in the paper, but it would have made it only more cumbersome and there are already enough many new concepts there…
      Cheers, Valerio

      • Ok then, I was not sure about that… I should have read the proof 😉 Shame on me !
        One remark, though : your article is really interesting in the scope of any “super-relativity” theory (namely any other theory which would replace c by a new speed C, but keeps the same physics), I agree, but for me it is not clear at all that a “super-relativity” theory would replace relativity efficiently. By efficiently, I mean that its domain of applicability would be strictly bigger.
        For example, if neutrinos were traveling at speed v>c, is it clear for you that the super-relativity theory with parameter v will explain things we know plus CERN experiment ?

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