Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B How do you build a quantum suicide machine?

  1. Mar 12, 2017 #1
    Hey!

    I posted this thread hoping that there are experts about quantum physics here. Please if you do not know a lot about the subject, don't answer this question:

    First things first, to be clear: I’m NOT building a quantum suicide machine and I’m NOT trying to kill myself. I’m just curious about multiverse theory and quantum physics and want to know how to build one.

    If I’m not mistaken, the requirements are a subject, a kill mechanism, and a particle accelerator. But what exactly is a particle accelerator in this case and how do you build one? I know that the kill mechanism could be like a gun attached to the machine.

    I find the idea about quantum suicide and the multiverse theory very fascinating, the reason I ask this question is simply because I'm curious.

    Thanks!
     
  2. jcsd
  3. Mar 12, 2017 #2

    Nugatory

    User Avatar

    Staff: Mentor

    Could you provide some references to what you've been reading and what you mean by "the multiverse theory"? There's a pretty good chance that you have been misled by non-serious popular treatments of quantum mechanics.
     
  4. Mar 12, 2017 #3

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    There is no need to build a machine. If many worlds is correct (whatever "correct" means), then there are worlds where you are dead, worlds where you were never born, and worlds where you will live forever.
     
  5. Mar 12, 2017 #4
  6. Mar 13, 2017 #5

    DrClaude

    User Avatar

    Staff: Mentor

    If I build a quantum suicide machine and continuously monitor my state, I would be immortal through the quantum Zeno effect, even if Copenhagen is right! :oldbiggrin:
     
  7. Mar 13, 2017 #6

    Nugatory

    User Avatar

    Staff: Mentor

    You try it. I'll watch.
    (But please, first make me the beneficiary of your life insurance policy).
     
  8. Mar 15, 2017 #7
    There is no multiverse theory. Just the MWI of QM.
     
  9. Mar 17, 2017 #8
    Many worlds interpretations do not imply quantum immortality. That is a myth.

    MWIs in general suffer from a serious problem: there is no precise, generally accepted definition of what a MWI *is*. As such, many of the common statements regarding its parsimony and elegance refer to some intuitive idea of what properties one such formulation would have. The trouble with intuition is that different things are intuitive for different people, and often times concepts that were legitimate in other interpretations of quantum mechanics find their way into discussions of MWIs as if they were legitimate there also.

    The case of quantum immortality is even worse: it's the illegitimate borrowing of a concept that was never legitimate or precisely defined, namely, the relationship between wavefunction collapse and consciousness. These intuitions take consciousness as a primitive "thing" that splits as the worlds split. Your subjective experience then follows one of your "descendants" in Hilbert space, and as long as there is at least one you will never experience death. However, this metaphysical hypothesis about consciousness has no justification, and the fact that we "lose consciousness" all the time (typically once a day) means that Hilbert space doesn't care whether the computations happening in your brain are conscious or not. It's probably much more natural to regard consciousness as an emergent phenomenon that arises on timescales much longer than the typical decoherence time that leads to world-splitting, rather than a primitive substance that tracks states in Hilbert space. After the trigger on your quantum Russian roulette machine is pulled you might find "yourself" in a world where you are dead or one where you're alive, just as in ordinary Russian roulette.
     
  10. Mar 18, 2017 #9

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    There is no need to include consciousness in the discussion. You can also discuss the survival probability of a molecule, of a rock, or whatever, without changing the conclusion that it will break in many but not all worlds in MWI. The question "is that a desirable outcome?" is independent of that.
     
  11. Mar 18, 2017 #10
    That is correct. It is the unnecessary and illegitimate insertion of consciousness in the discussion, likely borrowed from Wigner-esque views of quantum mechanics, that leads to the fallacious conclusion of quantum immortality.
     
  12. Mar 18, 2017 #11

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    That's not what I said.

    You can discuss quantum immortality without considering consciousness or living objects at all.
     
  13. Mar 18, 2017 #12
    Quantum immortality is not just the trivial statement that some of your descendants survive, according to some omniscient meta-observer that, unlike the rest of us mortals, has access to all branches of the wavefunction. Quantum immortality is the belief that if you play quantum Russian roulette, you will never experience death. The entire thought experiment is framed from a subjective point of view.

    Otherwise, there is no distinction between many-worlds interpretations and other interpretations. All that a real observer can say, one that plays by the rules, is that you live or die with some probability, or that a molecule or a rock is intact or destroyed with some probability. That is true even if you play regular Russian roulette and your survival is conditioned solely on classical probabilities. Many worlds adds nothing.
     
  14. Mar 18, 2017 #13

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    For suitable definitions of "experience death", it is true but also trivial - and true in all interpretations of quantum mechanics. The difference in MWI: "You" will survive for sure in some worlds.
     
  15. Mar 18, 2017 #14
    Exactly.

    The only difference is to some omniscient Laplace demon who knows the entire wavefunction. From "your" point of view (really from the point of view of any observer), there is no difference. It's just not a useful thought experiment. It's not about physics.

    The original idea was that you could use quantum suicide to convince yourself, but not anybody else, that the MWI is correct. What I wish to emphasize is that you can't even convince yourself.
     
  16. Mar 23, 2017 #15
    How can the part about the worlds where you will live forever be true? If the universe ends in the heat death the probability for that will be 0.
     
  17. Mar 23, 2017 #16

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    There is always a "non-zero probability" (there is always a world in MWI) that something somehow resembling you stays together.
     
  18. Mar 23, 2017 #17
    How about an expanding universe driven by a cosmological constant which eventually empties out and leaves nothing behind? Surely no MWI forces and fluctuations/thermodynamical miracles can beat out the cosmological constant in the long run?

    By the way, so you really believe that you will transcend death and experience immortality?

    Please don't answer me with "one copy of me will and one won't" because that would be ignorant of my question. Do you believe that you can never end up in a branch where death is experienced and quantum immortality is viable?
     
    Last edited: Mar 23, 2017
  19. Mar 23, 2017 #18

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    No, I think it is pointless to spend much time wondering about those worlds with negligible amplitudes.
    Yes, they exist, with and without cosmological constant, but I don't care about them, in the same way as I don't care about events with 1010-10 probability in probabilistic interpretations.
    The question is ill-defined.
     
  20. Mar 23, 2017 #19
    But how do they exist with the cosmological constant? If the universe empties out there will be nothing that can fluctuate and guarantee immortality.

    The second question is not ill-defined, do you believe that you will die? Straightforward, a normal question. Saying that you dont care about low amplitude doesn't answer anything.
     
  21. Mar 23, 2017 #20

    Nugatory

    User Avatar

    Staff: Mentor

    The amplitudes decline asymptotically towards zero, but they never get to zero so there always remains some tiny but non-zero probability.
    That is a straightforward normal question that is pretty much unrelated to anything else we're discussing in this thread. Even classical thermodynamics admits of low probability outcomes in which things never die (assuming, for the sake of argument, that life is a mechanistic phenomenon completely described by physical laws).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How do you build a quantum suicide machine?
  1. Quantum suicide (Replies: 5)

  2. Quantum suicide (Replies: 8)

Loading...