- #1

Heidi

- 345

- 33

I wonder if in quantum mechanics the question "Did this event occur?" has a yes or no answer like in classical phyics or in our daily life.

We are accustomed to consider linear superpositions of states like "dead" and "alive"

but id "dead" is a state the death of the cat is an event. i wonder if we can have superposition of events.

the title ask if decoherence is necessary to observe something.

it seems that getting an measurement result needs an inernoment in which information is lost.

this needs that the measured state becomes no more pure density matrix.

there is a theorem telling us that we can extend the system to a bigger one in which the purity is conserved. in this bigger system we could say that no such measurement occured.

the problem is that decoherence is not question of point of view. it is a physical process.

can we say that what is physical in the smaller system becomes unphysical in the bigger one?