On 5/9/2013 7:49 AM, Telmo Menezes wrote:

I was thinking to quantum erasure experiments. We can make a wave >>"collapse", by some measurement, and still make it cohere again, by erasing >>the memory of the experience/the result of the experiment. If observation >>did collapse or select irreversibly, that could not make sense.> > >But it isn't a "measurement" if you can make it cohere again. A measurement >is irreversbile, "erasing" means reversing the process that, if it were not >erased could have become a measurement.But this implies that a human observer is needed for something to be a measurement. The fact that the outcome of the measurement is physically available in the universe is not enough.

`No, it doesn't imply that. Being available in enough, c.f. buckyball interference`

`experiments.`

Would you agree that, knowing the outcome of the quantum eraser experiment, the Copenhagen interpretation implies that observation by a conscious entity is necessary to define a quantum state?

`No. But I'm not a fan of the Copenhagen interpretation because it implies the Heisenberg`

`cut is physical, yet is determined by the experimenter.`

The Copenhagen interpretation seems to require two magic steps (consciousness causing wave collapse and "pure randomness"). It seems to be a more extraordinary claim than the MWI. Also, CI + the quantum eraser experiment implies that stuff doesn't exist when no one is looking. Am I wrong (honestly asking)?

`I think you are assuming that there are only two possible QM interpretations: Copenhagen`

`and MWI. There is also the epistemological interpretation; the wave function is just our`

`description of the system and so it changes when we get new information (i.e. a`

`measurment). There is also decoherence theory, which attempts to described the physical`

`process of MWI. And there are several variants of MWI. And Mermin's "relations without`

`relata". As well Bohm's guide waves and some actual collapse theories.`

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