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Time Symmetric Quantum Mechanics

  1. Aug 28, 2013 #1
    I've been seeing more and more papers that seem to suggest Time Symmetric Quantum Mechanics (TSQM) is becoming the more parsimonious explanation to some newer experiments.

    For those unfamiliar with this formulation, it's a two-state-vector formulation, with one of the state vectors propagating backwards in time from the future (don't worry, causality is preserved!)

    Here's one, although from 2012:


    So, is this formulation being taken more seriously these days? The recent QM interpretation polls sure didn't seem to indicate that it is, despite these recent experiments.
  2. jcsd
  3. Aug 28, 2013 #2
    More from the Intro. Sounds like a rather Lorentzian/Minkowskian way of viewing things ;-)

  4. Aug 28, 2013 #3
    Huw Price writes quite a lot about this, here is his most recent paper: http://arxiv.org/abs/1307.7744
  5. Aug 28, 2013 #4
    I have not had time to read about Time Sym QM, yet. But it sounds similar to the old Transactional Interpretation. Is anyone here familiar with that? How does Time Symmetric QM differ from the Transactional Interpretation?

  6. Aug 29, 2013 #5
    That was a very cool article, thanks for sharing.

    I'm really quite surprised by the lack of interest in this flavor of QM. With it's increasing utility and elegance with explaining some recent experiments, plus the mind-blowing physical interpretation, it's hard to believe more folks aren't interested in exploring this interpretaion/formulation.

    With that said, it does sound like support is growing for it.
  7. Aug 29, 2013 #6


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    Very nice paper, but what I would like to see, if even for a toy example, is how complex amplitudes--the sort of mathematical tools used in standard quantum mechanics--can be understood in terms of retrocausality. Cramer's Transactional Interpretation sort of seems to be close to doing this, but I don't see how it relates to Huw's concept of retrocausality.

    Why does the whole mechanism of Hilbert spaces and Hermitian operators and so forth work so well?
    Last edited: Aug 29, 2013
  8. Aug 29, 2013 #7
    I think you'll get what you're looking for here:


    and here:

  9. Aug 29, 2013 #8
    Yes it surprises me too. Recently Wikipedia included it in the "traditional" interpretations of QM http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics. Given its characteristics described in that page (locality, determinism, non contextuality, unique history, etc) I smell that this interpretation is somekind of direction of the next theory of "super super tiny particle physics". But Im clearly not the one to state this kind of propositions.

  10. Aug 30, 2013 #9


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  11. Aug 31, 2013 #10
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  13. Nov 26, 2013 #12
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  15. Nov 27, 2013 #14


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    Last edited by a moderator: May 6, 2017
  16. Nov 27, 2013 #15
    This is a great experiment and if this is true it answers the question from my last my thread. Why is the probability the amplitude multiplied by its complex conjugate ... Maybe the joint probability of the wavefunction meeting itself coming the other way through time is the reality as we perceive it?
  17. Nov 28, 2013 #16
    excuse me, which thread ?

    point of encounter of the two vectors ? -> reality ?

  18. Nov 28, 2013 #17
    Why is probability amplititude squared? Last post was on the 26th. Sorry I don't know how you make a link to it.
  19. Nov 28, 2013 #18

    then, delve please.

    two vectors in time, one forward and one backward.

  20. Nov 29, 2013 #19


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    Thanks for the advert, Doc :smile: Here is our most recent work on RBW (to appear in IOP book on quantum spacetime): http://arxiv-web3.library.cornell.edu/abs/0908.4348v11. It's a paper with a long history, as is evident by the "0908" prefix. This version was posted on 18 Nov 2013 and will likely be the last, since it's now scheduled for publication.

    RBW is a time-symmetric interpretation of QM in the trivial sense that it's a blockworld interpretation. However, there are no quantum entities (wave function or otherwise) moving through the experimental equipment to 'cause' detector outcomes. So, RBW isn't really cast in the spirit of TSQM where paths through spacetime connect detector outcomes with emission events allowing one to tell 'causal' stories (if you allow for the future to 'cause' events in the past). We think of TSQM as a dynamical interpretation, since it tells stories using worldlines. RBW on the other hand is an adynamical interpretation, since the fundamental rule isn't about interacting, time-evolved things, but a self-consistency criterion applied to the action which characterizes the spatiotemporal configuration as a whole (to include outcomes). The idea of finding a rule for the construct of the action is certainly not new, but we are looking at it in an entirely new way. Our view is very similar to http://www.mdpi.com/2073-8994/3/3/524 that I posted earlier (Wharton et al). We differ from Wharton et al in that RBW allows relationships to exist between events that aren't connected by a contiguous mediating entity in spacetime. We used this idea to explain the Union2 supernova data without accelerated expansion or dark energy Classical & Quantum Gravity 29 055015 (2012) http://arxiv.org/abs/1110.3973, so it's not without empirical consequence.
    Last edited by a moderator: May 6, 2017
  21. Nov 30, 2013 #20

    then is acausal and static.
    and how can exist actions in an acausal and static framework ?

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