1 point
We can observe the end result. E.g. observing the screen only, and you get wavelike behaviour. When you also observe the slit, the wavelike behaviour disappears, and it seems particle like.
Both end in an observation, 1 has an extra observation.
1 point
yeah so if I looked at a log of all that, wouldn’t I have a “extra observer” detector, then?
2 points
You could detect decoherence in the system, that doesn’t indicate a human observer, however.
That process is, however, used to protect cryptographic keys, transfered between banks. A hostile observer collapses the state early. The observer gets the key instead of the 2nd bank, which is extremely conspicuous to both banks.
