# Are the wave-functions in surrounding objects collapsed?

Can we say that the wave functions in a cup of tea, a blanket, a stool, and other surrounding objects, are collapsed due to the constant interaction of these objects with photons and other radiation?

• Veritasium discusses this on the way to the Many Worlds interpretation of quantum mechanics. Parallel Worlds Probably Exist. Here’s Why Commented Aug 4 at 13:11
• Indeed, copious interaction with the environment all but guarantees decoherence, so, effectively, collapse. Commented Aug 4 at 19:48
• Suppose a system is constrained as follows: $\frac{w}{x}=1, \frac{y}{z}=1$. Then $w,x,y,z$ are underdetermined ($w=x, y=z$) but at the same time ${w,x}$ and ${y,z}$ are non entangled. Suppose a measurement now applies equal action to both system: $x\frac{w}{x}=1, x\frac{y}{z}=1$. This collapses $w=1$ entirely, but at the cost of entangling $\frac{xy}{z}=1$ more complicatedly than before. As no distances are recorded anywhere in the systemic constraint, separating different components of the system by any distance does not destroy the system entanglement $\frac{xy}{z}=1$. Commented Aug 4 at 20:48
• @CosmasZachos Suppose one constructs a macroscopic spherical ball with very symmetrical atom placements, symmetrical energies, etc, and shield this ball very well from the environment. Then this macroscopic object should be exhibiting un-collapsed quantum behavior (since decoherence stems from environmental interactions which is introducing various a-symmetries to the systemic constraint), correct? Commented Aug 4 at 21:40
• "shield this ball very well from the environment"... Unrealistically theoretical, you want a quantum-coherent microscopic object, as do the quantum computer engineers... When you give your practical details to your quantum decoherence expert, he is guaranteed to shoot it down. This is what Decoherence is all about. Commented Aug 4 at 21:47

Yes, the wave functions of the systems you mentioned like a cup of tea or a blanket are almost constantly collapsed. They almost never get a chance to evolve for very long in a unitary manner.

One could argue that in the many worlds interpretation, they are not collapsed, as mmesser314 mentions in a comment. But on the other hand, once you ask a question about "this" cup of tea or "that" blanket, you are restricting the system under consideration to be the system that roughly corresponds with what you in this world are observing. And in this world, the effective wave function of that subsystem remains collapsed.

If you do an experiment to test quantum theory in general the outcome can only be explained if the system goes through all of the possible states because anything that happens to any of the possible states changes the probability of the outcome. But when you do a measurement you only see one of the possible states. Many physicists state that the explanation for this is that when you do a measurement all of the other states disappear: this is called collapse. There are several problems with the idea of collapse.

The first problem is that it is unnecessary to explain the results of experiments. The equations of motion of quantum theory say that when you measure a system in general there are multiple outcomes. But when information about a system is copied out of that system, quantum interference is suppressed: this is called decoherence:

https://arxiv.org/abs/1911.06282

Since macroscopic objects like human bodies, chairs, books, computers and anything large enough for you to see are being monitored by interactions with light, air molecules and so on they are all decoherent and don't undergo interference on the scales of space and time we can see to a very good approximation.

This explains why we only see one outcome of an experiment when quantum theory - the other outcomes occur but they no longer interfere with the outcome we see. This is often called the many worlds interpretation but it is just a consequence of quantum theory when it is interpreted as one would interpret any other physical theory:

https://arxiv.org/abs/1111.2189

So why would you modify the theory when it already explains what we see and experimental results?

When people talk about collapse they usually don't give any explicit model of the collapse process, so it is just loose talk of the sort that shouldn't and wouldn't usually be accepted in science because it is untestable. In addition, collapse of the kind people usually talk about is incompatible with most of quantum measurement theory, e.g. - repeated and continuous measurements:

https://arxiv.org/abs/1604.05973

Also, if collapse happens it is both non-local and non-Lorentz invariant as shown by Bell's theorem and Hardy's experiment:

https://arxiv.org/abs/quant-ph/0410160

As a result both collapse theories and pilot wave theories are incompatible with relativistic quantum theories. So far, they have not been able to reproduce the tested predictions of such theories. The vast bulk of actual experimental results explained by quantum theories are relativistic, e.g. - all tests of Bell's theorem involving photons, so collapse theories fail to explain almost all real quantum experiments:

https://arxiv.org/abs/2205.00568

So collapse is unnecessary to explain the results of many known experiments and it is incompatible with the existing explanations. The objects you see around you are decoherent they have not collapsed.

• Can we say that since I always see the cup as red, this means that all the wave functions of the cup collapsed at the moment the materials it was made from were created, and have remained collapsed for millions of years? This is because the properties of the cup remain unchanged and predictable, even if I place it in a vacuum-sealed cabinet and then take it back out. Commented Aug 5 at 9:03
• The material the cup is made of decohered. It didn't collapse. Commented Aug 5 at 9:51