Does the superposition have a weight?

In summary: QM, but also to the theory of relativity and the theory of quantum mechanics themselves.What are "interpretations" of QM?What are "interpretations" of QM?
  • #1
timmdeeg
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Consider the double slit experiment performed on a extremely sensitive scale, whereby the whole device including source and detector is isolated. From energy conservation we would expect that the weight is constant in principle while the experiment is running.

What would we conclude? That the "which slit" superposition has a weight? Or if otherwise what has a weight? And how does either possibility relate to "ontic"?
 
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  • #2
timmdeeg said:
What would we conclude? That the "which slit" superposition has a weight?

That the whole device inside the isolation box has a weight. That includes the source and detector as well as the quantum system emitted by the source and detected by the detector.

Why do you think any of this is an issue?
 
  • #3
PeterDonis said:
That the whole device inside the isolation box has a weight. That includes the source and detector as well as the quantum system emitted by the source and detected by the detector.
This was the point of beginning. Can we just say that the quantum system has a weight without any further specification? Is saying the quantum system, meaning the superposition, has a weight tantamount to saying the wave function is ontic? What precisely has a weight?
 
  • #4
timmdeeg said:
Can we just say that the quantum system has a weight without any further specification?

If you're measuring the weight, which you are in your example since it's sitting on a scale, then sure, why not?

timmdeeg said:
Is saying the quantum system, meaning the superposition, has a weight tantamount to saying the wave function is ontic?

Does reading the weight on the scale tell you whether the wave function is ontic? No. All interpretations of QM make the same predictions for experimental results. That means you can't differentiate between interpretations (and "wave function is ontic" is an interpretation) by looking at measurement results.

Again, why do you think any of this is an issue?
 
  • #5
When you measure a superposition, you get 'particles' so you will get mass.
If you do a measurement and don't find 'particles', you obviously get no mass. 'Particles' bring mass via the Higgs field.

What does this question aim to prove?
 
  • #6
EPR said:
When you measure a superposition, you get 'particles' so you will get mass.
It seems the superposition has a mass before measurement, before I get particles.
 
  • #7
PeterDonis said:
Does reading the weight on the scale tell you whether the wave function is ontic? No.
The meaning of ontic "is physical, real, or factual existence" [Wikipedia]. This seems to apply to something which has a weight. So if not the wave function what else exactly is ontic?
 
  • #8
timmdeeg said:
It seems the superposition has a mass before measurement, before I get particles.
That's too many assumptions and drawing a conclusion out of your hat. Idle talk is discouraged here.
 
  • #9
timmdeeg said:
It seems the superposition has a mass before measurement

You said weight, not mass. They're two different things. Which do you want to talk about?

timmdeeg said:
if not the wave function what else exactly is ontic?

Um, the thing that's sitting on your scale?

You still haven't answered my question: Why do you think any of this is an issue? To illustrate why I'm asking that question, consider the following:

Suppose that we have a second scale sitting right next to the first one (the one you described in your OP), with an apparatus sitting on it that is exactly the same as the one on the first scale except that there is no double slit: a quantum thingie just travels from the source to the detector. The source is the same, the detector is the same, everything else is the same.

Do you think the same issue you are asking about in the first scenario (the one you described in your OP) still applies in the second scenario (the one I just described above)? If so, why? If not, what's the difference between them?
 
  • #10
PeterDonis said:
You said weight, not mass. They're two different things. Which do you want to talk about?
Um, the thing that's sitting on your scale?

You still haven't answered my question: Why do you think any of this is an issue? To illustrate why I'm asking that question, consider the following:

Suppose that we have a second scale sitting right next to the first one (the one you described in your OP), with an apparatus sitting on it that is exactly the same as the one on the first scale except that there is no double slit: a quantum thingie just travels from the source to the detector. The source is the same, the detector is the same, everything else is the same.

Do you think the same issue you are asking about in the first scenario (the one you described in your OP) still applies in the second scenario (the one I just described above)? If so, why? If not, what's the difference between them?
Agreed there is no difference.

Are quantum systems physical objects with physical properties?
The situation has been tentatively expressed in terms of various “interpretations”, conceived not only with regard to the physical meanings of mathematical quantities, but also in connexion with philosophical statements about “physical reality”. The question of whether quantum theoretical quantities describe or not definite physical systems existing in nature has been therefore generally considered as escaping the possibilities of physics, because of the definitions that are commonly taken for “physical state” and for “physical quantity”.

Weight is a physical property. If quantum systems have a weight (#4) they are real in the sense of having a physical property. But this is different to saying the wave function is real, right? In contrast to the latter the former statement is not an interpretation.
Well, after rethinking I agree the weight of a quantum system isn't an issue.
 
  • #11
timmdeeg said:
Agreed there is no difference.

Ok. Then "superposition" has nothing to do with it, so this in your OP...

timmdeeg said:
That the "which slit" superposition has a weight?

...is irrelevant to the issue you were raising.

timmdeeg said:
Weight is a physical property.

In quantum terms, it's an observable.

timmdeeg said:
If quantum systems have a weight (#4) they are real in the sense of having a physical property.

Meaning, you can measure the weight observable and get a value. Yes.

timmdeeg said:
But this is different to saying the wave function is real, right?

Yes, because the wave function isn't an observable. The fact that you can measure observables and get values is interpretation independent; it's part of the minimal QM that every interpretation must account for. But whether or not the wave function is real is not.
 
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  • #12
PeterDonis said:
Yes, because the wave function isn't an observable. The fact that you can measure observables and get values is interpretation independent; it's part of the minimal QM that every interpretation must account for. But whether or not the wave function is real is not.
Great, thanks for clarifying this. I avoid to say issue.
 
  • #13
This may enflame an interpretational war due to conservation laws, but some macro experiments(SQUIDS with macro currents flowing both ways, quantum computers, c60's etc.) imply some 'realness' aspect to the wavefunction. It's hard to understand from a classical perspective what really happens but it appears that it does take place at least from a weak measurement perspective.
 
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  • #14
EPR said:
This may enflame an interpretational war due to conservation laws, but some macro experiments(SQUIDS with macro currents flowing both ways, quantum computers, c60's etc.) imply some 'realness' aspect to the wavefunction.

This is off topic for the current thread. If you want to discuss these experiments and their implications for QM foundations and interpretations, please start a separate thread in this forum (and give an appropriate reference to a paper or papers as a basis for discussion).
 

1. Does the superposition have a weight?

The concept of superposition in quantum mechanics refers to the ability of a quantum system to exist in multiple states simultaneously. It is not a physical object and therefore does not have a weight in the traditional sense. Instead, it is described by a mathematical function called the wave function.

2. How does superposition affect the weight of an object?

Superposition does not directly affect the weight of an object. The weight of an object is determined by its mass and the force of gravity acting on it. However, in quantum mechanics, the concept of weight is replaced by the concept of probability, where the wave function describes the probability of finding the object in a certain state.

3. Can superposition be observed in everyday objects?

Superposition is a fundamental principle of quantum mechanics and can be observed in all quantum systems, including everyday objects. However, the effects of superposition are usually only noticeable at the microscopic scale, such as in the behavior of subatomic particles.

4. How is superposition related to the uncertainty principle?

The uncertainty principle states that it is impossible to know both the position and momentum of a particle with absolute certainty. Superposition plays a role in this principle because the wave function, which describes the position and momentum of a particle, can have multiple possible values at the same time, making it impossible to determine a precise value for either property.

5. Can superposition be observed in macroscopic objects?

Although superposition is a fundamental principle of quantum mechanics, it is difficult to observe in macroscopic objects because the effects are usually too small to be noticeable. However, there have been some experiments that have demonstrated superposition in larger systems, such as a superconducting circuit or a vibrating membrane.

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