Re: What are wavefunctions?

`On Sat, Dec 28, 2013 at 8:32 PM, meekerdb <meeke...@verizon.net> wrote:`
```
>  On 12/28/2013 4:45 PM, Jason Resch wrote:
>
>
>
>
> On Sat, Dec 28, 2013 at 7:12 PM, meekerdb <meeke...@verizon.net> wrote:
>
>>  On 12/27/2013 10:31 PM, Jason Resch wrote:
>>
>>  To that I would add the purely epistemic "non-intepretation" of Peres
>>> and Fuchs.
>>>
>>
>> "No interpretation needed" -- I can interpret this in two ways, one way
>> is to just take the math and equations literally (this leads to Everett),
>> the other is "shut up and calculate", which leads no where really.
>>
>>
>>
>>
>>>
>>>
>>>
>>>>  2. Determined by which observer? The cat is always either dead or
>>>> alive. It's just a matter of someone making a measurement to find out.
>>>>
>>>
>>>  So are you saying that before the measurement the cat is neither alive
>>> nor dead, both alive and dead, or definitely alive or definitely dead?  If
>>> you, (and I think you are), saying that the cat is always definitely alive
>>> or definitely dead, then about about the radioactive atom? Is it ever in a
>>> state of being decayed and not decayed? If you say no, it sounds like you
>>> are denying the reality of the superposition, which some interpretations
>>> do, but then this leads to difficulties explaining how quantum computers
>>> work (which require the superposition to exist).
>>>
>>>
>>>  Superposition is just a question of basis.  An eigenstate in one basis
>>> is a superposition in another.
>>>
>>>
>>  Can you provide a concrete example where some system can simultaneously
>> be considered to be both in a superposition and not?  Is this like the
>> superposition having collapsed for Wigner's friend while remaining for
>> Wigner before he enters the room?
>>
>>
>>>
>>  ?? Every pure state can be written as a superposition of a complete set
>> of basis states - that's just Hilbert space math.
>>
>>
>  So then when is the system not in a superposition?
>
>
> When it's an incoherent mixture of pure states.
>

What makes it incoherent though?  An electron in a superposition, when
measured, is still in a superposition according to MWI. It is just that the
person doing the measurement is now also caught up in that superposition.

The only thing that can destroy this superposition is to move everything
back into the same state it was originally for all the possible diverged
states, which should practically never happen for a superposition that has
leaked into the environment.

Jason

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