Does the superposition have a weight?

[timmdeeg]

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"?

 

[PeterDonis]

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?

 

[timmdeeg]

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?

 

[PeterDonis]

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?

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?

 

[EPR]

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?

 

[timmdeeg]

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.

 

[timmdeeg]

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?

 

[EPR]

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.

 

[PeterDonis]

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?

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?

 

[timmdeeg]

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.

 

[PeterDonis]

Agreed there is no difference.

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

That the "which slit" superposition has a weight?

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

Weight is a physical property.

In quantum terms, it's an observable.

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.

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.

 

[timmdeeg]

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.

 

[EPR]

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.

 

[PeterDonis]

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).