B Superposition particles in a box

[Dillon B]

If I had a box with a bunch of particles in superpositions in it, what would I find if I found the mass of the box?
First: Is it possible to have have box like this? If not what about theoretically.
Second: Does weighing the box collapse the superposition of the particles?
Third: Could I, by weighing the box without particles in it then with superposition particles in it determine the mass of the objects inside without collapsing their states?
Fourth: If no to 3, then how can measuring the box have any effect on the particles in the box?
Fifth: Am I missing something that make this all irrelevant and impossible?

I'm probably missing something here, thanks to anyone who can help me.

 

[andrewkirk]

1. Yes. In fact, systems are always in superposition from some perspectives.
2. In most interpretations of quantum mechanics, there is no such thing as collapse. Instead, one talks in terms of decoherence. But, in the loose sense in which it is popularly thought about, Yes, weighing the box will cause some form of collapse. Whether the collapse is of interest depends on exactly what it is about the particles inside the box that we want to know.
3. No. We cannot weigh something without in a sense collapsing some of its wavefunctions.
4. Because to weigh something, the scale must interact with the thing being weighed. That interaction between the systems generates decoherence, which is thought of as 'collapse'. In this case, the interaction is via two sub-interactions: Scale tray to Box, and Box to Particles inside.
5. No, the questions are perfectly reasonable from the point of view of a non-physicist. The difficulty is that the notion of 'collapse' is not well defined and even less well understood. To the extent that it means anything definite, that thing is not what many non-physicists think it means.

 

[mfb]

3. No. We cannot weigh something without in a sense collapsing some of its wavefunctions.

We can keep all the superpositions we might be interested in, however.

 

[PeterDonis]

If I had a box with a bunch of particles in superpositions in it, what would I find if I found the mass of the box?

Strictly speaking, we can't answer this question because we don't have a theory of quantum gravity. (I'm assuming that the superposition you are describing includes states that have different energies and therefore different masses.)

 

[mfb]

Quantum mechanics works perfectly well with weak gravitational fields. As an example, we can observe neutrons "bounce" above a surface - with well-defined quantum states.

 

[vanhees71]

Quantum mechanics works perfectly well with weak gravitational fields. As an example, we can observe neutrons "bounce" above a surface - with well-defined quantum states.

https://arxiv.org/abs/hep-ph/0306198
https://arxiv.org/ct?url=http://dx.doi.org/10%2E1103/PhysRevD%2E67%2E102002&v=7f2e8557

 

[Trollfaz]

Doesnt the box itself measure the particles and results in collapse?

 

[Nugatory]

Doesnt the box itself measure the particles and results in collapse?

That depends on the details of the interaction between the box and the particles.