On 9/19/2011 6:13 PM, Darren New wrote:
> On 9/19/2011 17:06, Patrick Elliott wrote:
>> you have to have the particle pair you are testing
>> with "interact" with something. That interaction, as I said in the other
>> post, is almost never, if ever, the measuring device.
>
> I don't understand how you decouple the two. You shoot a photon at a
> photomultiplier. The photomultiplier emits a click. The interaction
> causes the measurement. I don't know how you take a measurement without
> an interaction of *some* sort, and I don't know how you interact with
> something without taking a measurement unless you entangle your state
> with the device with which you're interacting.
>
In this case, yes. But you are forgetting the "other" condition of the 
test, i.e., placing something into the path of one of the entangled 
particles, thus causing it to change state, thus resulting in it never 
"being" detected. The point being, the state changes, regardless of 
whether your "detector" is the thing that changed it, or something else 
did. Thus, they are decoupled, in the sense that the detector, and thus 
observation, is not needed to collapse the state. Its merely incidental 
that, when you allow the detector to be the state changer, it both 
"changes" the state, and "measures" the result.

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