Quantum Superposition & Philosophy

[ZapperZ]

You may again be missing the essential metaphysical or philosophy of science issue here.

Central to the concept of classicality is locality. And therefore what strict classicality requires is the localisation of all properties of particles. The weirdness of QM is that measurements such as position~momentum are not commutative. You cannot localise the properties to an instant in spacetime as strict classicality would require.

Yes, you can still use the classical concepts themselves individually and orthogonally. In fact it is a major finding that there is a tight dichotomous relationship between complementary forms of measurement. We can start building a revised metaphysics based on this new concept (complementarity).

But it is quite wrong to say that QM does not challenge a central plank of classical physics. Patently it does.

I think it is my turn to say that you are missing my point here. I'm not arguing that QM is different than classical physics! This would be silly. I use QM ALL THE TIME! I've been trained as a condensed matter physicist, a subject area that was built on QM! In fact, I'll even point out that superconductivity, which is an area of study in condensed matter, in the words of Carver Mead, is the clearest manifestation of quantum phenomena anywhere in nature!

So are we clear now about the validity of QM?

What I pointed out to be wrong is the claim that one can get completely away from classical concepts. I even listed examples of what I said to be classical concepts, such as position, momentum, spin, energy, etc.. etc. Why are they classical concepts? Because they represent observables that we know of, AND, they represent the outcome of our measurements. All measurements that we make are inherently classical, because the system will interact with a large degree of freedom to make itself known to produce a particular observable outcome!

I'm not particular impressed with "building a revised metaphysics" (whatever that means) when people trying to do that have a faulty understanding of what they are using as building blocks! I'm not here to participate in such a building (I'm already busy building my own project, which is an actual build, rather than a metaphysical one). What I'm pointing out is that people here do not seem to CARE that they have either an ignorant, or a lack of, understanding of the things they are discussing or using.

I don't know if this is the ONLY area of study where people who are not experts in a particular subject area are told that "Hey, you might want to double check what you are using. That is not really correct!", they turn on you! You are welcome to "metaphysicalize" all you want, but if you do that based on a lack of understanding of what you are using, don't you think this requires correcting?

I have already stated why I think the understanding of "quantum superposition" that has been discussed has been severely lacking. I just don't TELL people that. Instead, I obviously "wasted" my time and effort to try and give as clear as an explanation that I can! But somehow, that explanation offended SOME people!

Zz.

 

[apeiron]

I'm not particular impressed with "building a revised metaphysics" (whatever that means) when people trying to do that have a faulty understanding of what they are using as building blocks! I'm not here to participate in such a building (I'm already busy building my own project, which is an actual build, rather than a metaphysical one). What I'm pointing out is that people here do not seem to CARE that they have either an ignorant, or a lack of, understanding of the things they are discussing or using.

We can all agree it is a great advantage to really understand what you want to discuss - and if not, be here to learn. In the past, you have pointed me at some key recent QM experiments, which I appreciate.

But there seems less point jumping up and down in a philosophy sub-forum about people wanting to do too much philosophy for your tastes. We get that you can get by in your daily work without raising wider questions.

Now back to the essential point. You are incorrect if you say that using classical concepts in a non-commutative fashion is the same as using them in the commutative fashion that classicality presumes.

Can you provide some argument that locality - the core concept in the classical view, as the nearest philosophy of physics book on my bookshelf attests - does not demand that properties of particles be localised in spacetime?

If attempts to localise one kind of measurement sends the other off into orbit, then that is a clear breach of classicality.

Yes, you may be happy to ignore this metaphysical difficulty, shrug your shoulders and say I still use classical concepts to make my measurements. In my working life, I step over the gapping holes in the principle of locality.

But you have not shown that the gap doesn't exist. And you are demonstrating a faulty and misleading understanding of the metaphysics if you continue to insist there is no issue. Is this really your intention here?

 

[pftest]

This quote fits in nicely here:

"If you are not completely confused by quantum mechanics, you do not understand it."
- John Wheeler

 

[Maui]

Yes, if you are claiming that you can find empirical evidence that does not make one single use of those classical concepts that I've stated! I would LOVE to see such empirical evidence out of SR and QM, especially considering that my line of work is nothing but experiments involving both of those fields.

Let's focus on wave-particle duality. The classical picture is supposed to be a 'wavicle'. So what is a "wavicle"? An object, idea, knowledge, bit, me, you, god? Can you ever know based on the classical concepts?(that's a rhetorical question of course)
I am not arguing that it IS 100% possible to imagine or comprehend a non-classical reality, I'm not certain myself, but i was pointing out the need to soften the classical grip to break new grounds.

I don't think you can either, because the phrase "classical description of superpositional states" can't be found in classical mechanics/wave mechanics text. Did you just made it up as you go along?

Yes, it's not in the textbooks, because there is no classical description and it defies imagination. But if you look at the top of the page, it says "philosophy forum", so I am sure you wouldn't be breaking any rules if you engaged in the philosophical implications of observed non-classical behavior.

When you make a measurement, the OUTCOME is classical! If you make a measurement of the ENERGY eigenvalue of a quantum state, that concept of energy is CLASSICAL! Now, the BEHAVIOR of the energy eigenvalue may be described via quantum formulation (i.e. it is quantized, have specific values, will only go through one slit or the other), but the CONCEPT OF ENERGY itself is classical!

This appears to be something very difficult for you to understand, even after being told repeatedly.

It's not what i was saying, this is probably the 10th time i will point out that that what you measure is classical, but what you don't isn't. That which you measure is how the world responds to your methods of inquiry(not what the world is or how the world is), and that which you don't measure is what the world actually IS(a grand unified field, a non-classical world or whatever you want to name it). The knowledge about that which is unmeasured is inferred from experiment such as the twin-slit, the dce, Delft/Stony Brook SQUID experiment, etc.

You somehow cannot distinguish that the concept of position is classical, but that position value itself can be dynamically described quantum mechanically.

It's misleading to say that a position of an electron is always classical. It's not, it's all over the place, all it takes is knowledge about the other noncommuting variable. A wavepacket is not a classical concept as well.

I've argued where your responses are wrong in terms of physics. All you have done is argue why my responses are wrong based on your TASTES! It is why I put no emphasis on your opinion that I don't understand superposition.

Zz.

Okay, let me re-phrase one more time - it's obvious that the world exists and that it doesn't succumb to a coherent classical description(impossible to interpret in a classical way fundamental building blocks of matter acting on a dynamical spacetime). Is this the universe's fault or are YOUR instruments and methods of inquiry/analysis at fault?

 

[Maui]

But it is quite wrong to say that QM does not challenge a central plank of classical physics. Patently it does.

Don't worry, he doesn't understand much of anything as far as how everything is supposed to fit in a coherent world picture, based on those classical concepts. And you are right that the philosophical baggage of QM is enormous.

 

[ZapperZ]

Let's focus on wave-particle duality. The classical picture is supposed to be a 'wavicle'. So what is a "wavicle"? An object, idea, knowledge, bit, me, you, god? Can you ever know based on the classical concepts?(that's a rhetorical question of course)
I am not arguing that it IS 100% possible to imagine or comprehend a non-classical reality, I'm not certain myself, but i was pointing out the need to soften the classical grip to break new grounds.

This is where you confused over the main issue. A 'wave-particle' isn't a "measurement or an observable"! It is a generic description of a series of observation in which a system behaves like a classical wave or a classical particle. Thus, when we apply it to our knowledge of classical physics, we say that that system has a wave-particle duality.

But "wave-particle duality" doesn't exist in QM! Read the FAQ in the General Physics forum! Yet, even in making such measurement, we have to determine location (i.e. position), especially in those which-way experiments! These are classical parameters inside a quantum description!

Your example has continued to prove my point. I'm still waiting for your example that does not use such classical concepts.

Yes, it's not in the textbooks, because there is no classical description and it defies imagination. But if you look at the top of the page, it says "philosophy forum", so I am sure you wouldn't be breaking any rules if you engaged in the philosophical implications of observed non-classical behavior.

But you asked for a measurement to be determined, which is now in the realm of physics (since when is a physical measurement done in Philosophy?). The "topic" may be philosophy, but if you use physics concepts as the topic of discussion, then it must also be valid in physics. If not, you are not discussion philosophy of science, and you're doing the same type of garbage that the worst of post-modernists did to science (and got soundly embarrassed by the infamous Sokal Hoax). If that is what you are doing here, you are also in violation of the PF Rules.

It's not what i was saying, this is probably the 10th time i will point out that that what you measure is classical, but what you don't isn't. That which you measure is how the world responds to your methods of inquiry(not what the world is or how the world is), and that which you don't measure is what the world actually IS(a grand unified field, a non-classical world or whatever you want to name it). The knowledge about that which is unmeasured is inferred from experiment such as the twin-slit, the dce, Delft/Stony Brook SQUID experiment, etc.

This makes no sense.

If what I measure is represented by eigen operators, and each of them produce results are are classical (as even you admitted), then these are classical parameters/concepts! Observables in QM are x (position), p (momentum), H (energy), etc... etc... The Hamiltonian/Schodinger equation is built using these quantities. So while the evolution and description of these parameters are quantum mechanical and not classical, these parameters themselves are STILL CLASSICAL AND HAVE CLASSICAL DEFINITIONS!

So for the 10th time or more, that is THE WHOLE POINT THAT I'VE BEEN TRYING TO GET ACROSS TO YOU!

It's misleading to say that a position of an electron is always classical. It's not, it's all over the place, all it takes is knowledge about the other noncommuting variable. A wavepacket is not a classical concept as well.

Read above! The way the position of an electron is described by QM is NOT classical. But the concept of position itself is classical! It is why we go "huh?" when we look at how QM grabs hold of this concept and caused it to produce very weird, non-classical description.

Furthermore, what does "non commuting variable" have anything to do with the spread in position? The spread in position observable has nothing to do with that observable commuting or non-commuting with another observable. This is highly puzzling.

Okay, let me re-phrase one more time - it's obvious that the world exists and that it doesn't succumb to a coherent classical description(impossible to interpret in a classical way fundamental building blocks of matter acting on a dynamical spacetime). Is this the universe's fault or are YOUR instruments and methods of inquiry/analysis at fault?

No one is saying that classical description works all the time! I have NEVER said, in any of the post, about classical description dominating all of physics. This is what you kept harping on, and you need to stop it.

Do yourself a favor, and look at the Schrodinger Equation. Pay attention to the parameters used in that equation (i.e. either the Laplacian, or if in 1D, the spatial derivative). Those parameters are classical. The equation is quantum mechanical!

Now, which part of that did not NOT understand?

Zz.

 

[ZapperZ]

Don't worry, he doesn't understand much of anything as far as how everything is supposed to fit in a coherent world picture, based on those classical concepts. And you are right that the philosophical baggage of QM is enormous.

To understand the baggage of QM, you have to understand QM first, and not simply some superficial idea of what it is, which was what has been demonstrated on here. You think the philosophical baggage of QM is enormous? You haven't even seen anything yet! You guys are still arguing about "superposition" and "duality", etc... while the rest of us have gone on to observe "spin-charge separation" and "low-dimensional universe"... etc.

But of course, *I* don't understand much of anything as to how these things are supposed to fit in. It requires a lack of understanding of QM as a required skill to be able to see such a thing.

Zz.

 

[apeiron]

If what I measure is represented by eigen operators, and each of them produce results are are classical (as even you admitted), then these are classical parameters/concepts! Observables in QM are x (position), p (momentum), H (energy), etc... etc... The Hamiltonian/Schodinger equation is built using these quantities. So while the evolution and description of these parameters are quantum mechanical and not classical, these parameters themselves are STILL CLASSICAL AND HAVE CLASSICAL DEFINITIONS!

So for the 10th time or more, that is THE WHOLE POINT THAT I'VE BEEN TRYING TO GET ACROSS TO YOU!

Thank you for correcting your statements to accord more with the facts. Classical parameters used within a quantum mechanical setting.

But this still creates the valid metaphysical issue of how we now conceive of this QM context - what is our concept of that? Despite your 10th go round, you still seem to believe this is not something that is a rightful topic for others to be discussing here.

Are you denying that locality is a central plank of the classical view? It is for instance what allowed Newton to talk intelligibly about velocity - change at an infinitesimal instant. And QM is non-classical in that it had to give up this central plank of classicality (even if still retaining other bits of the observational furniture such as position and momentum).

You can't have it both ways - insist that others recognise what aspects of classicality are preserved in QM, yet not yourself acknowledged what aspects got junked.

The wavicle, complementarity principle, hidden variables, many worlds, and other such concepts have indeed been attempts to rethink what a quantum reality might mean.

There is an important point being buried here - that in fact we don't have to completely abandon classicality and jump to some new bizarre QM metaphysics (like MWI or observer-created realities for example). Saner middleground approaches like environmental decoherence are emerging - which you could say deliver quasi-locality. It would be nice if these were a popular topic of discussion.

But instead we are only hearing the extreme views - either that there are no answers at all (if you think you understand QM, then you prove you don't really), or that we should not even be asking the questions,

 

[Maui]

The forum ate a rather long reply i made(it logs me out constantly) . I'll see if i can find the motivation to write it again today.

 

[Maui]

But this still creates the valid metaphysical issue of how we now conceive of this QM context - what is our concept of that? Despite your 10th go round, you still seem to believe this is not something that is a rightful topic for others to be discussing here.

Reminds me of a quote from a well known movie:

"The fish doesn't think, because the fish knows everything"

This is where you confused over the main issue. A 'wave-particle' isn't a "measurement or an observable"! It is a generic description of a series of observation in which a system behaves like a classical wave or a classical particle. Thus, when we apply it to our knowledge of classical physics, we say that that system has a wave-particle duality.

Yes, a "wave-particle' is just a generic description, and very misleading at that, BECAUSE it's classical and inadequate. There is no classical picture for what a 'wavicle' is, hence you(and everyone else) are forced to acknowledge that you don't know what anything really is. That's why i insisted that we need to soften up the grip on the classical concepts. On a more personal level, i find it much more consistent to think of the universe in terms of relations, not in terms of objects, ala Carlo Rovelli's:

"Quantum mechanics is a theory about the physical description of physical systems relative to other systems, and this is a complete description of the world"

though, philosophically, that statement is lacking in content and is missing something essential.

But "wave-particle duality" doesn't exist in QM! Read the FAQ in the General Physics forum! Yet, even in making such measurement, we have to determine location (i.e. position), especially in those which-way experiments! These are classical parameters inside a quantum description!

So what are you arguing about? Just everyone agrees that using the established scientific method, we can only conclude that the quantum world is primary(if not fundamental), whereas the classical is only a limited, special case.

Your example has continued to prove my point. I'm still waiting for your example that does not use such classical concepts.

I never argued that we don't use classical concepts, but that they are often inadequate. Again, i don't see what this argument is about. People of the same opinion don't argue.

But you asked for a measurement to be determined, which is now in the realm of physics (since when is a physical measurement done in Philosophy?). The "topic" may be philosophy, but if you use physics concepts as the topic of discussion, then it must also be valid in physics. If not, you are not discussion philosophy of science, and you're doing the same type of garbage that the worst of post-modernists did to science (and got soundly embarrassed by the infamous Sokal Hoax). If that is what you are doing here, you are also in violation of the PF Rules.

We are doing physics even before we make a measurement to get a classical result. Yes, calculations are physics. Those calculations tell us something about the world that doesn't fit the classical worldview.

This makes no sense.

If what I measure is represented by eigen operators, and each of them produce results are are classical (as even you admitted), then these are classical parameters/concepts! Observables in QM are x (position), p (momentum), H (energy), etc... etc... The Hamiltonian/Schodinger equation is built using these quantities. So while the evolution and description of these parameters are quantum mechanical and not classical, these parameters themselves are STILL CLASSICAL AND HAVE CLASSICAL DEFINITIONS! So for the 10th time or more, that is THE WHOLE POINT THAT I'VE BEEN TRYING TO GET ACROSS TO YOU!

I agree, but that was not my point. There is no disagreement on what you are saying which is fairly obvious.

Read above! The way the position of an electron is described by QM is NOT classical. But the concept of position itself is classical! It is why we go "huh?" when we look at how QM grabs hold of this concept and caused it to produce very weird, non-classical description.

No disagreement here.

Furthermore, what does "non commuting variable" have anything to do with the spread in position? The spread in position observable has nothing to do with that observable commuting or non-commuting with another observable. This is highly puzzling.

The spread in position is determined by knowledge of the other non-commuting variable - momentum. Same with wave-particle duality.

No one is saying that classical description works all the time! I have NEVER said, in any of the post, about classical description dominating all of physics. This is what you kept harping on, and you need to stop it.

Do yourself a favor, and look at the Schrodinger Equation. Pay attention to the parameters used in that equation (i.e. either the Laplacian, or if in 1D, the spatial derivative). Those parameters are classical. The equation is quantum mechanical!

Now, which part of that did not NOT understand?

Zz.

We are not arguing any more.