[ExI] Criticisms of Many Worlds Interpretation (MWI)

[Stuart LaForge]

On 2023-09-15 05:29, Jason Resch wrote:
> On Fri, Sep 15, 2023, 12:16 AM Stuart LaForge via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
>> This means that the counterfactual photon caused a counterfactual
> .> bomb
>> to explode, destroying itself in the process, and preventing it from
>> 
>> interfering with the observed photon. This causes the photon to only
>> 
>> take one path, end up at detector B, and thereby prove that the bomb
>> is
>> live and not a dud. It would not make sense that the photon would
>> not
>> blow up the bomb and not interfere with itself unless something
>> happened
>> to the other photon. Stuff that does not happen should not be able
>> to
>> cause stuff to happen here. Unless the stuff that doesn't happen
>> here
>> happens in another universe and that is what causes stuff to happen
>> here
> 
> How is this experiment any different from any single photons
> interferometer experiment (where we say, replace the bomb with a red
> or blue stained piece of glass) and use photons from a red light
> laser, and use photon arrival locations to infer the color of the
> glass placed in the path of one of the photons?

It's not different. The bomb detector was a thought experiment, but 
since physicists didn't want actual bombs going off in their lab, they 
confirmed the predictions of the thought experiment using an experiment 
very similar to one you discuss here.

> It's less explosive than a bomb (just an explosion of some IR photons
> after the photon gets absorbed by the blue glass). But the outcomes
> are the same.
> 
> It also seems to be equivalent to the two slit single electrons
> experiment where we put a detector at only one slit and don't observe
> the electron there.

Yes, the two-slit single-electron experiment with a detector at one slit 
is pretty close to the bomb tester

> I haven't seen people say before that these experiments confirm MW.

I wouldn't say confirm, but merely add credence to, like a larger 
posterior probability. Incidentally, the authors of the original 
experiment say by way of explanation on 
https://www.tau.ac.il/~vaidman/lvhp/m28.pdfpage 993 of their 1993 paper:

"In the MWI there is no collapse and all "branches" of the photon's 
state (5) are real. These
three branches correspond to three different "worlds." In one world the
photon is scattered by the object, and in two others it does not. Since 
all
worlds take place in the physical universe, we cannot say that nothing 
has
"touched" the object. We get information about the object without
touching it in one world, but we "pay" the price of interacting with the
object in the other world."

https://www.tau.ac.il/~vaidman/lvhp/m28.pdf

> They do, of course, confirm a superposition of particle positions, but
> that has never been the issue with CI. CI accepts the superposition,
> it only adds that it disappears after an observation is made, whatever
> that may be, even if the observation happens to be "not observing an
> electron go through the right slit" or not observing an explosion of
> IR photons in the blue stained glass.

Yes but how CI and MWI resolve the superposition is at the crux of their 
difference. Both interpretations agree that the superposition of a 
quantum 6-sided die would be a linear sum of the states 1 through 6:

|1> + |2> + |3> + |4> + |5> + |6>

The difference happens when a measurement is made. Lets say you roll the 
die and observe a "6". In CI, that means the terms |1> + |2> + |3> + |4> 
+ |5> of the superposition, which were actual states a moment ago, are 
destroyed or simply cease to exist.

In MWI, however, when you make an observation, the superposition simply 
separates into its component states with each sorting into their own 
timelines: A|1>, B|2>, C|3>, D|4>, E|5>, and F|6>. So if you observe a 
"6", you discover that you are observer "F" in the F timeline.


> So I am curious what you see in the Elitzur-Vaidman bomb test that
> implies MW. (If it's anything above and beyond the other superposition
> affirming experiments I mention above).

The Elitzur-Vaidman bomb tester and the experiments you mention above 
are not affirming superpositions, they are affirming that they are 
superpositions of real states. Only something real can cause something 
to happen in the real world. If something counterfactual is causing 
observable events in the real world, that counterfactual thing has to 
real too. It's just real somewhere else.

Stuart LaForge