Is there experimental evidence of a single, free massive particle wavefunction can spread in space to macroscopic size?
Thanks for the answers
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Theoretically, this is possible (as are a lot of things, as it turns out). However, there are a few issues with determining something like this experimentally.
Although I can't be certain, due to the reasons listed above, I doubt there is experimental evidence that a free particle wavefunction can be macroscopic.
Suppose you prepare identical particles in an identical free state. That is, they have the same spread in space. You send them in opposite directions.
If you make position measurements on the particles on one side after a time that is much shorter than the measurements that you make on the particles on the opposite side, you'll see that the spreading in space of the first particles will be much smaller than that on the opposite space.
The longer you wait to measure the second part of the particles (i.e. you measure their position after a sufficiently long time), the bigger the spread, which can reach macroscopic measures.