Why is the "conscious observer" thing considered?

[Sayestu]

TL;DR

Is it possible that observing e.g., a measuring device's result could collapse the wave function?

Question from someone scarcely more knowledgeable on QM than a layperson. To my understanding, early in QM's study, some thought observation by a conscious being was required to collapse a wave function. I was told here that said Copenhagen interpretation(?) is only considered by people like Deepak Chopra now, because things like machines can perform measurements. Is it possible conscious observation of the device's result would actually be what causes collapse?

 

[Nugatory]

Is it possible conscious observation of the device's result would actually be what causes collapse?

When you follow that line of thinking you run up against all the same paradoxes as the with the original “consciousness causes collapse”idea, except with the device instead of the original particle being observed.

David Lindley’s book “Where does the weirdness go” is layman-friendly explanation of how the quantum decoherence eliminates the need to involve conscious observers in collapse.

 

[Standard]

An explanation :

Ever since quantum mechanics was first formulated, Nature has been divided into two categories: the classical world (that of tennis balls) and the quantum world of atoms and atoms and photons. The transition between the two is achieved by wave function collapse during the measurement process. From the multitude of possible measurement results included in the wave function, only one value emerges, the one actually measured, corresponding to a particular state of the wave function. This is an irreversible process, quite different from the (reversible) evolution of the system just before the measurement according to Schrödinger's equation.
Two worlds and two types of dynamics... too complicated!

Another approach is possible by considering that everything is of a quantum nature: the system under study, the measuring apparatus, the observer and even the watch that marks the time at the moment of measurement. A researcher in the INSP's Aggregates and Surfaces under Intense Excitation (ASUR) team has demonstrated that with this approach, the probability function of the measurement results is simple and unique. What's more, it is valid for both tennis balls and photons.
Translated with DeepL.com (free version)

https://w3.insp.upmc.fr/wp-content/uploads/2022/09/Faitdactu_ASUR_Trassinelli_sept_2022.pdf

Here the Arxiv link :
https://arxiv.org/abs/2103.08903
https://arxiv.org/pdf/2103.08903

 

[Lord Jestocost]

TL;DR Summary: Is it possible that observing e.g., a measuring device's result could collapse the wave function?

Question from someone scarcely more knowledgeable on QM than a layperson. To my understanding, early in QM's study, some thought observation by a conscious being was required to collapse a wave function. I was told here that said Copenhagen interpretation(?) is only considered by people like Deepak Chopra now, because things like machines can perform measurements. Is it possible conscious observation of the device's result would actually be what causes collapse?

Freeman Dyson in “THE COLLAPSE OF THE WAVE FUNCTION” in John Brockman’s book “This Idea Must Die: Scientific Theories That Are Blocking Progress" (New York, NY, USA: HarperCollins (2015)):

“Fourscore and eight years ago, Erwin Schrödinger invented wave functions as a way to describe the behavior of atoms and other small objects. According to the rules of quantum mechanics, the motions of objects are unpredictable. The wave function tells us only the probabilities of the possible motions. When an object is observed, the observer sees where it is, and the uncertainty of the motion disappears. Knowledge removes uncertainty. There is no mystery here.

Unfortunately, people writing about quantum mechanics often use the phrase “collapse of the wave function” to describe what happens when an object is observed. This phrase gives a misleading idea that the wave function itself is a physical object. A physical object can collapse when it bumps into an obstacle. But a wave function cannot be a physical object. A wave function is a description of a probability, and a probability is a statement of ignorance. Ignorance is not a physical object, and neither is a wave function. When new knowledge displaces ignorance, the wave function does not collapse; it merely becomes irrelevant.”

 

[Fra]

A wave function is a description of a probability, and a probability is a statement of ignorance. Ignorance is not a physical object, and neither is a wave function. When new knowledge displaces ignorance, the wave function does not collapse; it merely becomes irrelevant.”

I agree with Jestcosts quote, but closest thing we can get to "physical meaning", here is that while the "information" itself about a system isn't "physical", it requires a physical context for it beeing ENCODED. Similar to disorders in classical sics, the entropy requires a an actual microstructure whose macroscate ENCODES the entropy.

In the copenhagen interpretation, this physical context is the macroscopic environment (the "classic" side of the heisenberg cut). The "collapse" to the extent that one can argue it beeing physical, thus occurs as changes in the microstate of the "environment". It's not the quantum system itself that "collapses."

/Fredrik

 

[bhobba]

Historically, it dates back to some stuff written by von Neumann about where to place the classical to quantum cut.

Things have moved on since then, and most now place it where decoherence occurs.

Thanks
Bill

 

[Demystifier]

The wave function tells us only the probabilities of the possible motions. When an object is observed, the observer sees where it is, and the uncertainty of the motion disappears.

This looks to me as if Freeman Dyson thinks that a particle has motion and position even when we don't observe it, while observation just reveals the position that the particle had just before the measurement.

 

[Fra]

Historically, it dates back to some stuff written by von Neumann about where to place the classical to quantum cut.

Things have moved on since then, and most now place it where decoherence occurs.

The macroscopic environment? But exactly where does the macroscopic environment start?

I think this view, pushes the explanatory perspective (the "old cut") to an asyptotic perspective.
Is this a substantial improvement or just a waty to push the problem away?

/Fredrik

 

[bhobba]

The macroscopic environment? But exactly where does the macroscopic environment start?

Now, you are starting to move beyond popularisation to the genuine issues of QM, and this is one of the things Einstein and his good friend Bohr debated.

Interesting possible answers have been found in in modern times:
https://arxiv.org/abs/1312.7454

Thanks
Bill

 

[Nugatory]

But exactly where does the macroscopic environment start?

That question seems to me analogous to questions such as when we can start applying the ideal gas law to systems of multiple non-interacting particles. We choose what's system and what's environment according to what make the problem at hand tractable.

 

[Fra]

Now, you are starting to move beyond popularisation to the genuine issues of QM, and this is one of the things Einstein and his good friend Bohr debated.

Interesting possible answers have been found in in modern times:
https://arxiv.org/abs/1312.7454

Different questions can be asked depending on what kind of explanation you seek (in this is I think where the interpretetional stance enters). All "explanations" rests of something, some assumptions or some type.

The paper you refer to essentially seeks to ask "how does classical realm emerge from a quantum world". They see the universe as a closed system. This way of asking the question is IMO completely missing an important part of the problem. It is not a complete solution in my view, it is I think part of the answer, but the fine tuning parts and understanding how interactions are unified remains. For me they should be solved together. Not solving one, at the expense of make the other problem even bigger.

That question seems to me analogous to questions such as when we can start applying the ideal gas law to systems of multiple non-interacting particles. We choose what's system and what's environment according to what make the problem at hand tractable.

I see your point, but for me at least, the question implicit in the ponderings is much deeper than that. For me it's not about making things tractable as effective models, but conceptually consistent with the explanatory model you seek.

Are the "foundations of QM" just about the only bohr/einstein debates? I think not. For me the foundation of QM are enangled with BTSM problems such as unification. This is more easily realized as the spacetime is a prerequiquite for defining QM. in in BTSM, cosmology or bigbang, spacetime is one of the things that needs to be explained! And in this "explanation" all the interactions are unavoidalbe entangled.

/Fredrik