On Friday, October 18, 2019 at 1:36:33 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Thursday, October 17, 2019 at 6:05:00 PM UTC-5, Brent wrote:
>>
>>
>>
>> On 10/17/2019 2:35 PM, Bruce Kellett wrote:
>>
>> I think you have misunderstood the experiments. The interference pattern
>> is present if the welcher weg information is erased, whether the erasure
>> takes place before or after the photons hit the screen. If the information
>> is not erased, no interference pattern is seen, even if the idler photons
>> drift off to infinity.
>>
>> * > Deutsch was simply wrong when he thought that his experiment would
>>>> "prove" the existence of many worlds.*
>>>>
>>>
>>> Actually Deutsch didn't say that, he said his experiment would test Many
>>> Worlds not prove it correct.
>>>
>>
>> OK. But the alternative that Deutsch seems to have been testing was that
>> only a conscious observer could collapse the wave function. As I have said,
>> this has never been a serious scientific position.
>>
>> When the exparament is actually performed for all I or Deutsch knows it
>>> could prove that the Many Worlds idea is dead wrong. I've already told you
>>> what my best guess on the outcome so what is your prediction? When that
>>> photographic plate is developed will there be interference bands on it or
>>> not?
>>>
>>
>> If the welcher weg information is quantum erased, then there will be an
>> interference pattern, whether or not it is a conscious observer who is
>> erased.
>>
>>
>> In Carroll's version of the experiment, which has been performed
>> arXiv:quant-ph/9903047 v1 13 Mar 1999, the experimenter who arranged that
>> each electron has its welcher weg recorded by a spin UP (left slit) or spin
>> DOWN (right slit) particle does, at the end of the experiment, knows
>> there's a record of which slit each electron went thru, and he can sign an
>> affadavit that says that information is known. But he doesn't know it
>> *consciously*; it's recorded by all the spin particles, but not in his
>> memory that he can bring to consciousness. We know what happens if he
>> signs such an affadavit or if he doesn't, it's the same: if the recording
>> spin particles are measured in a left/right basis the information is erased
>> and the interference pattern can be discerned by considering only particles
>> that measured left or only those measuring right.
>>
>> So Deutsch was proposing to test whether the* conscious *AI which could
>> have the recording particles as part of it's memory and presumably be
>> conscious of the up/down spins before they were erased would produce a
>> different result.
>>
>> But I wonder what happens in Carroll's experiment if, after measuring in
>> the left/right basis and noting that two different interference patterns
>> can then be discerned by considering either those due to left spin
>> recording particles or considering right spin particles, one measures the
>> recording particles again in the up/down basis. The overall pattern is the
>> same, it's just that you've relabeled spots on the screen according to
>> whether the second measurement of recording particles assigned them to UP
>> or to DOWN. Now you can consider the subset labeled UP (or DOWN). This
>> should be a superposition of ensembles randomly selected from the left and
>> right ensembles and in that case would not show an interference
>> pattern...but the information has certainly been erased (twice)?
>>
>> Brent
>>
>
>
>
> So, in the end, it seems that reading Carroll's book is a huge waste of
> time after all, if his "explanation" leads to confusion.
>
> @philipthrift
>
e.g. What Sean proposes is a middle decoherence [from his blog]:
The trickiness relies on the fact that by becoming entangled with a single
recording spin rather than with the environment and its zillions of
particles,
*the traveling electrons only became kind-of decohered*.
With just a single particle to worry about observing, we are allowed to
contemplate measuring it in different ways. If, as in the conventional
double- slit setup, we measured the slit through which the traveling
electron went via a macroscopic pointing device, we would have had no
choice about what was being observed. True decoherence takes a tiny quantum
entanglement and amplifies it, effectively irreversibly, into the
environment. In that sense the delayed-choice quantum eraser is a useful
thought experiment to contemplate the role of decoherence and the
environment in measurement.
In terms of Many Worlds, it sounds like a Middle World.
@philipthrift
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/fc86d1e2-785f-4611-90fa-bc26017db789%40googlegroups.com.
