[ExI] how heavy are double-slit apparatuses?

scerir scerir at alice.it
Tue Mar 18 17:35:44 UTC 2014


Rafal:

> But, if the weight of the macroscopic apparatus changes only by the weight
> of interfering entities, a very minute value, then perhaps it's something that
> has not been measured yet.

There is a general  theorem, the Wigner-Araki-Yanase (WAY) theorem, according to which the
presence of *a* conserved quantity imposes a limitation on the measurement process.

WAY showed that one cannot *precisely* measure observables which do not commute with
*that*
conserved quantity (no, nothing to do with HUP). There is a trade-off between the
distinguishability of the final states of the system under measurement and the apparatus.
The uncertainty of the measurement can be made arbitrarily small, provided that the
measuring apparatus is sufficiently large and heavy.

But I do not know whether that theorem may be relevant here, or not.

Notice that quantum interference experiments are not performed "in vacuo", in vacuum, and
sometimes they are also performed in water!

As for the `many interacting worlds' (MIW) interpretation it is possible, imo, that
conservation of energy doesn't apply (or must be redefined), like in MWI.





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