On 2/26/2015 10:11 PM, Jason Resch wrote:
On Thu, Feb 26, 2015 at 10:33 PM, meekerdb <meeke...@verizon.net
<mailto:meeke...@verizon.net>> wrote:
On 2/26/2015 7:48 PM, Jason Resch wrote:
On Thu, Feb 26, 2015 at 9:40 PM, Bruce Kellett <bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au>> wrote:
Jason Resch wrote:
On Thu, Feb 26, 2015 at 9:20 PM, Bruce Kellett
<bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au> <mailto:bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au>>> wrote:
Jason Resch wrote:
There's no problem defining probability. There is, however,
a
big problem defining collapse.
Collapse is easily defined.
So at what point does it happen?
What triggers it?
On what scales can and can't it happen?
The quantum bayesian answers are: When you learn the value.
When does that happen, and what defines/differentiates a learning being from any other
physical encoding/state of the environment?
Your learning.
Is that when some neuron in my brain releases neuro-transmitters a instantaneous FTL
collapse event propagates across the entire universe instantly destroying the
superposition no matter how far away elements of it might be?
?? It destroys the superposition in your mathematical description.
Is everyone else besides me unable to collapse the wave function, or is it only
me?
If you're in a box with a radioactive particle and Geiger counter, do you remain in a
superposition until I learn about your state (and cause a coherent and consistent
version of you with memories of the past hour in a box to spontaneously come into
existence)?
Not sure what "scales" refers to - probably any scale.
This was in reference to those who say the world is classical at some scales and quantum
mechanical at other (small) scales, unlike MW which admits the universe operates quantum
mechanically at all scales, always.
How do you define a measurement? An observer?
How is a measuring apparatus or an observer different from any other
physical object?
What is the special property of the observer / measuring device that
enables it to collapse the wave function?
If you have an observer who himself is isolated from an external
environment, can he collapse the wave function? Or can only you
collapse
him by observing him?
Note that all these questions about "an observer" apply equally to "who is
the first
person, that is indeterminate".
Questions about the first person are addressed by theories in philosophy of mind, not by
quantum mechanics. Collapse on the other hand is supposedly a quantum mechanical
phenomenon, not adequately explained or defined within the theory it is supposed to be a
part of.
Quantum bayesianism explains collapse as a mental event. It's quite consistent with
Bruno's idea of reversing psychology and physics since it makes physics just a way of
predicting experience.
Since collapse theories often connote special extra-physical abilities to the observer,
it becomes natural to wonder in what ways an observer is physically different from other
physical parts of the environment. Things are reversed under MW, which acknowledges no
physical distinctions or powers exist between the particles that compose an observer, or
any other particles or system.
It doesn't acknowledge a distinction but it uses one. It assumes that there is something
that "self-locates" while everything else remains in supersposition.
All these questions are rendered irrelevant if you take the view that
the wave
function is purely a device for calculating probabilities,
So it is easily defined, but when I ask what that definition is, I'm told
"shut up
and calculate!"
not something that has a real, independent existence. In other words,
the
epistemic interpretation of QM.
So then what was the universe before there were any observers? Did the
first mouse
to be born and open its eyes cause the creation of the universe?
An epistemic interpretation and observation is updating a theory of the
world just
like any other observation. Most theories of the world include a past.
But would that past not be a gigantic uncollapsed wave function for the entire universe,
since it had been evolving and splitting for aeons before anyone could learn anything?
You keep confusing quantum bayesianism with something like von Neumann's measurement
process. In QB observation is an epistemic event that takes place in a mind. "Collapse"
is a mathematical process of changing one's model on receipt of new information.
There is nothing physical to collapse -- we are dealing solely with
classical
probabilities.
If it's just a device for deriving probabilities, what is doing all the
work in a
quantum computer?
Rotation of the state vector in Hilbert space.
So it is real, and can do things even when not observed?
Depends on what you mean by "real". In QB it's not "out there", but it's part of your
model of the world.
Brent
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