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## Main Question or Discussion Point

When talking about measurement in QM it's completely normal to think right away about someone doing "something" to get or "observe" a definite quantum state....

......but how about the screen in a standard DS? ....there we get clumps if we measure a quantum state at the slits or fringes if not.....

...... can't we consider the screen a measuring device that can tell Alice if Bob measured a quantum state or not?....the no communication theorem applies to measurement of quantum states only, so.... does Alice really needs to see what Bob was doing at the slits to tell if Bob was measuring a quantum state or not?....

......but how about the screen in a standard DS? ....there we get clumps if we measure a quantum state at the slits or fringes if not.....

...... can't we consider the screen a measuring device that can tell Alice if Bob measured a quantum state or not?....the no communication theorem applies to measurement of quantum states only, so.... does Alice really needs to see what Bob was doing at the slits to tell if Bob was measuring a quantum state or not?....