On Tue, Apr 19, 2022 at 4:52 PM Quentin Anciaux <allco...@gmail.com> wrote:

> Le mar. 19 avr. 2022 à 03:20, Bruce Kellett <bhkellet...@gmail.com> a
> écrit :
>> On Tue, Apr 19, 2022 at 11:09 AM Brent Meeker <meekerbr...@gmail.com>
>> wrote:
>>> On 4/17/2022 1:45 PM, George Kahrimanis wrote:
>>> Just as in Schroedinger's famous example with the cat, you need a "box"
>>> and an observer outside, in order to make sense of the cat being in an
>>> entangled superposition. Instead of a superobserver, we can do with an
>>> impersonal quantum description (in any chosen frame of reference), if you
>>> prefer.
>>> The only purpose of the box in Schroedinger's thought experiment was to
>>> put off the observers perception.  Really the thought experiment is over
>>> when the radioactive decay occurs.  That atom has transitioned to a
>>> different nuclear state which is entangled with and recorded in the
>>> environment.
>> Yes. Schrodinger had the cat in a box to emphasize the idea that the cat
>> was in a macro-superposition of alive/dead. This misled Wigner to the
>> extent that he thought the state collapsed only when the box was opened.
>> All of this was made redundant when it was realized that decoherence
>>  rendered the state definite almost instantaneously. Saibal makes the same
>> mistake when he claims that Alice, after her measurement, is still in a
>> superposition until Bob sees her result. The idea that the superposition
>> still exists since decoherence is only FAPP is something of a red herring
>> -- in MWI, Alice has branched according to her result into up and down
>> branches that no longer interfere. There is no macro-superposition.
>> Bruce
> It's because Saibal sees observers as "machine"... so until anything is
> recorded in the machine available memory... it's in a superposed state.

I think you are referring to consciousness in quantum computers where there
is no decoherence. The trouble with this idea is that without decoherence,
no permanent memories can be formed, so it is difficult to know what
"observe" means in that context. In any ordinary machine, decoherence is
everywhere, so no superposition ever endures. Observers cannot be in
superposed states (observation requires the formation of records, and that
in turn requires decoherence, which destroys superpositions.) Saibal refers
to observation as "an algorithm". But without specifying what runs the
algorithm, his claim is devoid of meaning.


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