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B Double slit and DCQE with future prediction

  1. Dec 22, 2016 #1
    Tom Campbell posted a series of videos in youtube where he proposes a few variation of double slit and DCQE experiments that might support his theories. He claims that would be possible to predict a future atom decay or a beam splitter behavior that way.
    I am very interested about experiments 1c2 and 5:

    - Experiment 1c2: at 43:00
    - Experiment 5: at 47:30

    If you have the time and pacience to watch, I would like to know if those experiments are doable and what are your predictions of the outcomes.
  2. jcsd
  3. Dec 22, 2016 #2


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    It would be more appropriate, given forum rules, to provide a peer-reviewed paper to discuss.
  4. Dec 22, 2016 #3


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    Here is a relevant quote, from another place at which Tom Campbell's ideas are discussed :

    "It is sufficient to destroy the interference pattern, if the path information is accessible in principle from the experiment or even if it is dispersed in the environment and beyond any technical possibility to be recovered, but in principle still ‘‘out there.’’ The absence of any such information is the essential criterion for quantum interference to appear. "

    -Anton Zeilinger from this paper: Experiment and the foundations of quantum physics

    Please note that to the extent Campbell agrees with the above, Campbell would be with the mainstream (and there wouldn't be much to discuss). To the extent he disagrees, peer-reviewed sources must be provided.

    I think it is fair to describe Campbell's basic hypothesis as "consciousness causes collapse", which is controversial to say the least.
  5. Dec 22, 2016 #4
    Thanks for the reply DrChinese. I don't think there are any peer-reviewed just yet. These experiments are thought experiments.

    I am more interested in discussing the proposed experiments than Tom Campbells ideas in this post.

    Thanks again.
  6. Dec 22, 2016 #5


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    That's going to be difficult. There are no shortage of mainstream experiments that blur the lines between causal ordering, such as the Delayed Choice type. All of these follow normal QM. If you wanted to discuss those, that would be great. This forum is generally not the place to discuss ones that do not follow the mainstream and involve speculative physics. Further, it is generally not appropriate to post a video in place of a proper reference to a paper. The fact that there isn't one is an immediate red flag.

    I am passing this on as a friendly note as you are relatively new to posting here. :smile: Perhaps you can summarize the proposed experiment in a manner that would support further comment. I didn't read in depth, but I understand there is something about an envelope...
  7. Dec 22, 2016 #6
    No, nothing like that. He suggests a modification of the double slit and DCQE to predict the outcome of a future event (atom decay or BS behavior).
    I will try to summarize as soon as I get home. English is not my native language so it will not be easy task for me, thats the reason I've posted the youtube links (sorry about that).
  8. Dec 22, 2016 #7


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    It is already possible to predict the outcome of future quantum events with random outcomes (using entangled systems). I will be interested to see what new twist his experiment provides.
  9. Dec 22, 2016 #8


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    Is it just me or he does not know what a single slit pattern looks like?
    Like here:

    It seems that for him single slit pattern is just projection of the slit.
  10. Dec 22, 2016 #9

    Here is the experiment 12c. He says that we can ajust the interference pattern and the single slit pattern in such a way that they do not overlap so much on the screen (R3). Then he feeds the microprocessor attached to the screen detector (R3) with this results to create a algorithm, so he can predict if the photon arriving will be from a interference or single slit pattern.
    In the actual experiment, after the photon arrives to the screen, the signal of the wich way information is still traveling from detectors D1 and D2 to R1. There it will be a radioactive element that will determine if this information will be erased or not (random processes). So he believes that the microprocessor will predict with more than 50%, based where the photon lands on the screen, how the atom will decay in the future (erasing or not the wich way information).


    Here is the experiment 5. He does something similar to the experiment above. Puts a microprocessor attached to the signal photon screen to predict if the idler will reflect or not at BS1/ BS2, before it gets there.

    My questions remains. Are these experiments doable? What you think will be the outcome?

    Last edited: Dec 22, 2016
  11. Dec 22, 2016 #10
    First I have to apologize for being biased. I'm quite certain, based on standard QM theory, that the DCQE type experiment can't be modified so that you can predict, from the dot on the screen, which detector the idler photon will be found in. Furthermore I'm also convinced it doesn't matter whether a conscious being acts as the detector. Therefore, instead of studying it carefully, I'll just give my casual impression of the mistake Campbell's making.

    In the normal DCQE experiment you can't separate the two "single-slit" patterns from the "interference" pattern. All dots on the screen are spread over more or less the same area. The result is a large "gray" area (no pattern). If you get which-slit information you can do no more: there's no interference pattern and no way of recovering one. However if the idler photon hits the other pair of detectors you get phase info: they divide the dots into two groups by phase, depending on which detector is hit. Now, when you separate out those two groups you see two interference patterns which complement each other.

    The key point is: knowing where a dot lands on the screen (the signal photon) tells you nothing about which detector will be activated by the idler photon.

    Campbell says you can redesign the experiment so that, when which-slit information is known, the signal photon will land in one of two localized places. But when allowed to interfere it will land elsewhere. This would allow you to know which detector the idler photon is going to hit later on, even though it's supposed to be impossible to predict.

    For Exp 5 he says "1) Pick parameters so that the two bar pattern falls between diffraction peaks", no further details. (There's a similar bullet for 1c2). That can't be done, I believe. With a simple two-slit experiment you can do it, but that's without the downconversion to signal/idler photons, and the rest of the DCQE set-up. In fact Campbell's idea amounts to an impossibility proof, a proof by contradiction. If you could make such a DCQE experiment, you could predict something QM says you can't predict. The conclusion is impossible, therefore the premise is also.

    No doubt that can be shown more directly, analyzing the DCQE experimental design.

    If you can answer my objection, and explain in more detail how he intends to design such an apparently impossible DCQE experiment (i.e. unpack Exp 5, note 1), let me know. As far as I could tell with a few minute's perusal it wasn't covered in that video.

    BTW the thread will soon be blocked (my posts activate the patented PF "auto-block" feature) so, unfortunately, this is a futile exercise.
  12. Dec 22, 2016 #11
    Yes, this is something I was wondering too. I am not a physicist, that is why I asked if its doable. I think the ideas are great, but maybe there is no way to acomplish them.
  13. Dec 22, 2016 #12


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    Tom's already made his mistake by experiment 1a, in assuming that sending the two detector outputs to the same recorder will erase the which-way information and restore the interference pattern. Quantum mechanics is reversible. You can't crunch two input states into one output state. The only way to make this experiment work is to dump the which-way bit into the system's waste heat, which is going to collapse the system just fine. The result of the experiment is going to be no-interference-pattern.

    (An alternative strategy is to diagonal-post-select the bit out of your results after the fact. That's what most delayed-choice experiments are based on. But it doesn't seem applicable to this case.)

    These major oversights of trivial issues are why I consider Tom Campbell to be a crank. I listen to him talk, and I try not to laugh.

    Let me give another example of Tom not being worth listening to, but this time from computer science instead of physics. Tom says it's hard to reverse a simulation and so a simulated reality will always step forward. But actually it's really easy to make reversible simulations. Just take checkpoints and restore from backup. Or perform your updates on a persistent data structure and keep track of the old roots. Or do hierarchical memoization, like hashlife. Or use a debugger that does all this for you, instrumenting any program to allow rewinding. And note that the ability for simulations to be rewound is not some trivial point in Tom's arguments. The simulation having to move forward is how Tom intends to force a faux-pas out of reality.

    Tom Campbell's basic premises are wrong. His whole style of presentation reeks of using consciousness as a mysterious answer. He is not worth your time. And so I vote this thread be locked.
    Last edited: Dec 22, 2016
  14. Dec 22, 2016 #13


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    There is no such thing as "two bar pattern". In science we have to check our speculations against real observations. This men is obviously not doing that.
    Me too.

    EDIT: @TJung instead of watching videos of this Tom Campbell take a laser pointer and make a single slit diffraction yourself then you won't be fooled by such Tom Campbell next time.
    Last edited: Dec 22, 2016
  15. Dec 23, 2016 #14


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    As DrChinese has already pointed out, an acceptable source would be required for discussion, and there isn't one, so this thread is closed.

    (Btw @secur it wasn't your post that did it. :wink:)
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