Can the "measurement problem" just be an "epistemological ambiguity"?

[lawrencepatriarca]

TL;DR Summary

The "measurement problem" in QM might be an epistemological issue: in every domain the need for definite, non-contradictory descriptions can be achieved only if there is a clear frame of reference/perspective. Measuring a particle could simply mean "establishing that perspective".

Premise 0: sorry for the wall of text, I know it might seem like I'm posting a theory rather than asking a question, but I wanted to make my thought clear

Premise 1: This is not a TOE question; simply, it is the hypothesis that the "measurement problem" might not be a "real problem" at all. It might just be an epistemological misunderstanding.

Premise 2: In quantum mechanics, the measurement problem can be defined as "the problem of definite outcomes: quantum systems have superpositions, but quantum measurements only give one definite result".

Premise 3: The problem of definite outcomes— of univocal and definite results—reflects a "need" that we seem to have both in our daily life and in science: we want to achieve a "non-contradictory, univocal description of phenomena/events," which means that we do not want our propositions related to certain things/phenomena to be both true and not true at the same time and in the same sense ("in the same respect" to use Aristotle's words).

So, evidently, every description of a certain phenomenon, which aims to be "principle of non-contradiction compatible" (note: not "correct," or "meaningful," or "useful," simply PNC-compatible), needs to respect all the parameters of the definition of the PNC, including the third one, which is "in the same sense," "in the same respect." This roughly means "according to the same perspective."

A historically fundamental aspect of the scientific description of phenomena is the identification of parameters and criteria that allow for a unified frame of reference, valid for all observers in every circumstance. In other terms, a well-defined and shared perspective. The water is not hot for me or cold for you; it is 34°C. The road is not long or short; it is 439 meters. The car is not red to me in the day or black to you during night; it is made of a material that absorbs and reflects certain wavelengths rather than others.

This is even fundamental to the theory of relativity, where the concept of motion itself is relative: whether an object is at rest or in motion depends on the observer's frame of reference. An object's position and motion can appear differently to observers in different gravitational fields or different states of acceleration. In this domain, it is well understood that even the state of being "at rest" or "in motion" and the exact location of an object are not absolute concepts but depend entirely on the observer's frame of reference (perspective).

So I would say that we can all agree that if we want a PNC-compatible description of things (definite and univocal results), we have to have a clear, established perspective ("in the same respect").

In QM, the Schrödinger equation (the best equation we have) describes the quantum wave - and the quantum particles - as being in superposition, which is fine and good. But superposition is not a PNC-compatible description of reality (no definite and univocal results) because our propositions related to a certain particle can indeed be both true and not true at the same time and in the same sense (X it is at the same time a particle and a wave, X is at the same time in this place and in another place).

The many-worlds interpretation even states that "if we take the Schrödinger equation seriously", we should accept some sort of ontological mega-universe (the collection of all possible worlds) where the famous cat is both dead and alive, I am both rich and poor, life exists on Earth and does not, etc.

On the other hand, when we perform a measurement, we only observe definite results. The measurment problem. But.... why the surprise? I think we are missing the elephant in the room here.

The only known way to obtain univocal results (PNC-compatible) is by measuring/observing the particle with some device. And what does this truly mean, epistemologically? To establish the perspective, to declare the point of view, to make the frame of reference explicit. A double slit in nothing if not a perspective, a frame of reference.

We have to do—conceptually—the exact same thing in relativity (if we want a PNC-compatible, univocal description of motion or velocity).

Even radically, we have to do it with everything: temperature, charge, weight, color. If we don't establish a clear perspective, our descriptions will never be PNC-compatible (definite, univocal descriptions and outcomes).

The fact that our description of reality depends on the frame of reference—and the fact that if the frame of reference isn't the same, our propositions related to things might not be univocal and definite—is something easy to forget and take for granted. Why? Because the perspective is often implicitly shared (at least with sufficient aproximation), because of the common cognitive apparatus we all share as sapiens.

But when we approach the quantum world, somehow, this becomes something unacceptable: this becomes "a problem."

And so I arrive to my question.

"to measure" a particle might simply mean to establish a perspective (the experiment conditions, the positions, and features of the detector device, etc.)? Since only under an established perspective ("in the same respect") can things be described in definite, univocal, PNC-compatiblen terms?

Or am I missing some specific feature of QM that invalidate some previous passage?

Thanks for your patience and attention.

 

[Nugatory]

You speak of "the measurement problem", but you haven't actually stated what that problem is. If you were to do that it would be easier to consider whether you've addressed it.

However....

to measure" a particle might simply mean to establish a perspective (the experiment conditions, the positions, and features of the detector device, etc.)?

All of that is an essential part of any quantum calculation already. But after we've established that, when we do our quantum mechanical calculations, we get a probabilistic statement: "X% probability of result state A, y% probability of result state B, ....". There's just nothing in the theory that gets us from that statement to the fact that the system ends up in one of these states.

 

[lawrencepatriarca]

isn't premise 2 an acceptable definition?

 

[PeroK]

QM isn't a something that we chose to adopt based on an a priori philosophy. It was something nature forced on us - essentially in opposition to any preexisting philosophy of science.

 

[lawrencepatriarca]

QM isn't a something that we chose to adopt based on an a priori philosophy. It was something nature forced on us - essentially in opposition to any preexisting philosophy of science.

Maybe. But one could argue that the pre-existing philosophy of science (hardcore deterministic realism so to speak) was deeply flawed and QM simply forced us back to a more sophisticated "kantian" approach.

 

[Vanadium 50]

Is this a purely philosophical debate or is there some actual science involved?

 

[gentzen]

Premise 2: In quantum mechanics, the measurement problem can be defined as "the problem of definite outcomes: quantum systems have superpositions, but quantum measurements only give one definite result".

Have you ever heard of Arnold Neumaier's thermal interpretation?
https://www.physicsforums.com/threads/the-thermal-interpretation-of-quantum-physics.967116/
https://www.physicsforums.com/threads/more-on-the-thermal-interpretation.971000/
https://www.physicsforums.com/threa...-a-new-approach-to-quantum-mechanics.1011069/

He is also concerned with such problems. But my question to you: Even if it should be just an epistemological problem for the most part, how to you explain this to working physicists?

And so I arrive to my question.

"to measure" a particle might simply mean to establish a perspective (the experiment conditions, the positions, and features of the detector device, etc.)? Since only under an established perspective ("in the same respect") can things be described in definite, univocal, PNC-compatiblen terms?

Or am I missing some specific feature of QM that invalidate some previous passage?

Is this a purely philosophical debate or is there some actual science involved?

It depends: If the meaning of "to measure" is the only question, then there is not enough actual science involved. But if the question is to understand the problem of definite outcomes, then it is a different story.

 

[PeterDonis]

The problem of definite outcomes— of univocal and definite results—reflects a "need"

No, it reflects what we actually observe. We observe measurements to have definite outcomes. So our physical theory should predict that measurements have definite outcomes.

Your "wall of text" does not talk at all about what we actually observe.

This is even fundamental to the theory of relativity

Not the way you mean. Classical relativity predicts that when we make a measurement, we get a single definite outcome. All the things you talk about that are "relative" are not measurement outcomes. Measurement outcomes in relativity are represented by invariants, and invariants are the same regardless of all the things you say are "relative". That is why there is no "measurement problem" in classical relativity.

 

[PeterDonis]

it is the hypothesis that the "measurement problem" might not be a "real problem" at all. It might just be an epistemological misunderstanding.

Have you read any of the literature on the measurement problem in QM? If not, you should. It is not a good idea to try to come up with a hypothesis on your own about physics, particularly about something like the measurement problem in QM, while being ignorant of the existing state of knowledge in the field.

 

[lawrencepatriarca]

No, it reflects what we actually observe. We observe measurements to have definite outcomes. So our physical theory should predict that measurements have definite outcomes.

It seems to me that we observe definite outcomes - something can be described as a definite outcome, more precisely - only and only if we are related to an established perspective, an established frame of reference.

for example:

even at the quantum level we observe definite outcomes, if we have a clear perspective.
To my knowledge no electron has ever been measured to have spin up and spin down at the same time.

So... are you able to indicate a way other than setting up an experiment, or using a measurment device, to establish a prospective relationship, to establish a frame of reference, with the quantum phenomenon you intend to observe?

 

[Fra]

Premise 1: This is not a TOE question; simply, it is the hypothesis that the "measurement problem" might not be a "real problem" at all. It might just be an epistemological misunderstanding.

IMO, the "real problem" in the measurement problem is the fact that we lack a unified description(theory) of the dynamics of an isolated system, and the "dynamics" of an interacting observer (ie. making measurements).

The solution that we can incorporate the observer into the "system" is not a proper solution, as the solution escapes the problem by MOVING it to another observer level where the original system is different (and larger!).

So it is not just a philosophical misconception, I think the depth lies in understanding the nature of interactions from two different perspectives in a coherent way, which we still doesn't IMO.

/Fredrik

 

[PeterDonis]

for example

This is a pop science video and is not a good source for PF discussion. You need to reference textbooks or peer-reviewed papers.

 

[PeterDonis]

we lack a unified description(theory) of the dynamics of an isolated system, and the "dynamics" of an interacting observer (ie. making measurements).

This isn't really true. For realist interpretations of QM, we can write down such a dynamics using the Schrodinger equation with an appropriate Hamiltonian. The problem is that this dynamics, by itself, if we adopt a realist interpretation of the quantum state, tells us that measurements have all possible outcomes, not just one single outcome. We have to add some sort of "wave function collapse" to get single outcomes, and that has to be added to the dynamics by hand, with no good rule for when to do so other than "when it works".

For non-realist interpretations, "dynamics" is not a problem in the first place because the quantum state is not interpreted as being the physically real state of an individual system. In ensemble or statistical interpretations, for example, the state is simply a description of the probabilities of various possible measurement results (or, equivalently, of the preparation process that was used). Probabilities don't have dynamics.

 

[Fra]

I realize I was unclear as to what I wanted to say, what i meant implict but didn't write was maybe better:

We lack a unified description(theory) of the dynamics of an isolated system [from the perspective of an external observer], and the "evolution" of an interacting observer (ie. making measurements) [from the perspective of the observer itself]

On the difference on dynamics and just "lawless" evolution, it's something Lee smolin spend lots of time on. The concepts he explaine in talks and books makes that difference clear.


and
https://arxiv.org/abs/1201.2632

For me the connection to the OT is clear but perhaps the connection to the question requires a long train of thought, but it's what it is, it relates also to cosmological time (to which the dynamical law is not clear) and the normal time the parameterizes subcosmological processes, such as particle physics experiments. The key issue is that there are two timescales that interact, the timescale where the subsystem we observer change, and the timescale where the context change. And when the context, is suddently part of the system, we need to unify the notions somehow. But how?

/Fredrik

 

[Fra]

By the problem of different time scales, I associate that to the different levels of information processing capacity (computing power and memory capacity, which in some sense are likely bounded by the mass of the observing context) of various observers in the contect of them having to "respond" in a timley manner.

Meaning, an observer are du to limiting capacity of information processing, unable to "decode" sufficiently scramble information, BEFORE it must react back and take actions. Many conjecture thata black holes are the faster scramblers of information for example https://pirsa.org/09010033. In a way one can also see a "black hole" itself as an perhaps "optimal observer" in the generalized sense. An observer that extracts as much informaiton as possible, and use it to dominate it's environment, and that also dismisses what what - relative to itself is just noise (ie thermal hawking raidation), which is "maximally scrambled", relative to the mass of the black hole.

The "normal perspective" on which QFT builds, is that the whole macrocsopic environment is the "observing context" and its mass and informationa capacity limits is now explicit, but is rather assume unlimited. This is an idealisation, that is acceptable for alot of particle physics, but becomes a problem when looking to
- unify all interactions
- avoid fine tuning problems in unified models

This is what i read into the "problem of different time scales", many problems are also coceptually related, like the problem of time in quantum gravity etc, I think they are different symptoms of the same core problem showing up in different places.

/Fredrik

 

[PeterDonis]

Thread closed for moderation.