Interesting paper on QM in Scientific American

[bhobba]

I found the following interesting:
https://ctrk.klclick1.com/l/01KG5PPJ0FMG5PHBSE7YST7PXZ_12

I have no idea if you need a subscription to Scientific Amacan because I have one (not as big a fan as I once was, but its digital edirion is dirt cheap).

If you do let me know and I may be able to see if somthing can be done.

Thanks
Bill

 

[.Scott]

ctrk.klclick1.com

And you want to keep track of how many PF'ers are following your link?
I am guessing you are referencing this article. It opened for me without any paywall interference.

 

[PeroK]

I found the following interesting:
https://ctrk.klclick1.com/l/01KG5PPJ0FMG5PHBSE7YST7PXZ_12

I have no idea if you need a subscription to Scientific Amacan because I have one (not as big a fan as I once was, but its digital edirion is dirt cheap).

If you do let me know and I may be able to see if somthing can be done.

Thanks
Bill

What did you find intersting about it? It seemed to be the useful pop-sci. The ending is:

“The lesson may be,” de la Hamette says, “that we should not have forgotten the observer.”

In what universe has the observer in QM been forgotten?!

 

[Morbert]

"Inserting the observer into the Schrödinger equation, it seems, allows transformative new perspectives on century-old questions."

Von Neumann effectively did this almost a century ago in his Mathematical Foundations of Quantum Mechanics.

Nevertheless, It is a fundamental requirement of the scientific viewpoint -- the so-called principle of the psycho-physical parallelism — that it must be possible so to describe the extra-physical process of the subjective perception as if it were in reality in the physical world — i-e, to assign to its parts equivalent physical processes In the objective environment, In ordinary space. [...] In particular we saw in the four different possibilities in the example above, that the observer in this sense needs not to become identified with the body of the actual observer: In one instance in the above example, we included even the thermometer in it, while in another instance, even the eyes and optic nerve tract were not included. That this boundary can be pushed arbitrarily deeply into the interior of the body of the actual observer is the content of the principle of the psycho-physical parallelism — but this does not change the fact that in each method of description the boundary must be put somewhere, If the method is not to proceed vacuously, I.e., if a comparison with experiment is to be possible. Indeed experience only makes statements of this type: an observer has made a certain (subjective) observation; and never any like this: a physical quantity has a certain value.

I.e. While there is an observer-observed divide, the physical system of a human observer can always be placed on the "observed" side of the divide.

Apparently my most heterodox view is that the measurment problem has largely been solved for decades.

 

[pines-demon]

When I first started in PhysicsForums I used to just post links of articles I found interesting. Every time I got various messages telling me "what is interesting??", "do you have a question about it?" and "are you just link dumping articles?". So please consider telling us something personal about you and the article.

 

[WernerQH]

Perhaps the only interesting (?) fact was that the birth of wave mechanics was 100 years ago.

 

[bhobba]

What did you find intersting about it? It seemed to be the useful pop-sci. The ending is:

Fair enough.

I really should have said for: HS students at the pop-sci level.

Of course, at that level, there is confusion between a human observer and what an observation is in QM (i.e., an interaction between quantum objects).

I have no personal connection to the article, other than thinking it might be of interest to our beginner members.

Thanks
Bill

 

[Sambuco]

I.e. While there is an observer-observed divide, the physical system of a human observer can always be placed on the "observed" side of the divide.

What do you mean by that? In my opinion, von Neumann points out that the exact location of the Heisenberg cut is arbitrary, but that it must be somewhere, which could be interpreted as meaning that the observer as a whole cannot be on the side of the observed object.

Apparently my most heterodox view is that the measurment problem has largely been solved for decades.

I'm also intrigued by what you mean by this, but I suppose your answer to the previous question will shed some light on this.

Lucas.

 

[Morbert]

What do you mean by that? In my opinion, von Neumann points out that the exact location of the Heisenberg cut is arbitrary, but that it must be somewhere, which could be interpreted as meaning that the observer as a whole cannot be on the side of the observed object.

I mean plainly that the physical system of a human observer can always be placed on the "observed" side of the divide, as explained by von Neumann. I.e. It was understood by von Neumann that the body of an observer has a quantum mechanical description. The Scientific American article describes an approach that involves giving measurement devices a quantum mechanical description. It's perfectly good science (see https://www.nature.com/articles/s41467-018-08155-0 ) but in line with mainstream literature on quantum foundations.

 

[Andy Resnick]

I found the following interesting:
https://ctrk.klclick1.com/l/01KG5PPJ0FMG5PHBSE7YST7PXZ_12

I have no idea if you need a subscription to Scientific Amacan because I have one (not as big a fan as I once was, but its digital edirion is dirt cheap).

If you do let me know and I may be able to see if somthing can be done.

Thanks
Bill

The Sci. Am. article references this journal article by Witten et. al:

"But in a 2023 paper, a team of physicists, including the great theoretician Edward Witten, added an observer with a quantum clock to their treatment of a black hole and were surprised to find the gnarly math became simpler. Entropies that seemed infinite, impossible to calculate, suddenly became tractable. “If you take quantum reference frames into account, you find those infinities are made finite,” Kirklin says."

I think the paper is open access.

 

[Sambuco]

I mean plainly that the physical system of a human observer can always be placed on the "observed" side of the divide, as explained by von Neumann. I.e. It was understood by von Neumann that the body of an observer has a quantum mechanical description. The Scientific American article describes an approach that involves giving measurement devices a quantum mechanical description. It's perfectly good science (see https://www.nature.com/articles/s41467-018-08155-0 ) but in line with mainstream literature on quantum foundations.

Ok, I see. I'm sympathetic to the QRF program since it aligns with my relational view of quantum mechanics. In any case, although both consider that the observer is also made of quantum "stuff", to me von Neumann is merely arguing in favor of the well-known arbitrariness in choosing where to place the Heisenberg cut (shifty split).

Lucas.

 

[PeterDonis]

the physical system of a human observer can always be placed on the "observed" side of the divide

But then what is doing the observing?

Ultimately, we would like QM to not even have such a divide--to be able to describe everything without having to partition some things off as "observers" that aren't governed by the equations of the theory.

 

[bhobba]

But then what is doing the observing?

Von Neumann's famous writing on this in his classic text on QM never really caught on (and when I first read it, it left me scratching my head for reasons like you mention, e.g., exactly what is consciousness), but it did catch on with his good friend Wigner. However, later in life, after von Neumann's untimely death, influenced by Zeh's early writings on decoherence, he did a 180% because of its problems, advocating objective collapse theories. I like to think von Neumann, if he had been alive, would have changed his mind too.

Thanks
Bill