From: *Jason Resch* <[email protected] <mailto:[email protected]>>
On Mon, Jul 30, 2018 at 7:36 PM Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
On Mon, Jul 30, 2018 at 6:12 PM Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
On Mon, Jul 30, 2018 at 12:29 AM, Bruce Kellett
<[email protected]
<mailto:[email protected]>> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
On Mon, Jul 30, 2018 at 12:13 AM, Brent Meeker
<[email protected] <mailto:[email protected]>> wrote:
?? Quantum computers cannot calculate anything more
than classical computers. There are some algorithms
that allow a QC to calculate something faster; but
the domain and range is the same.
So absent that reason does it follow that the wave
function is merely a convenient (and very accurate)
tool?
Tool for what? Predicting probabilities of finally
measured values?
What then can we say about the intermediate values and
the computation itself? Does it exist and happen, or
does the final result merely materialize magically like
the live or dead cat?
Does the spot on the screen behind two slits materialize
magically? Or arise as a consequence of the interference
in the one world?
In many-worlds, all possible screen spots occur in
different worlds. But the separation into distinct
worlds happens only on decoherence at the screen -- the
interference all happens in the original single world.
What is the photon in each world interfering with?
It's a wave, so it's interfering with itself. Just like water
or sound waves.
You are saying "a photon is a wave" as if that is an explanation
and to avoid the main point. If a photon is a wave, and it is
interfering with other waves, then in other words, it's
interfering with other photons.
No, it is interfering with itself. Don't be mislead by the
water/sound wave analogy.
You can use "itself" only if this "it" can be in multiple locations
and heading in different directions.
That is a property of waves. But you will only ever observe a single
photon from this wave.....
On that we agree. But where did those other photons come from?
How did they get to be in different positions going in different
directions?
They aren't.
How do do you explain the experiment with beam splitters and
recombining light at a half silvered mirror to interfere and only be
reflected one way?
Photons have both wave-like and particle-like properties. That is
quantum physics.
Why do these "waves" (photons) behave in all the same ways as
photons, they reflect off mirrors, pass through strained glass (only
if the glass is the same color as the photon), are blocked by opaque
objects, travel at c, etc?
Ah, the mysteries of quantum physics. Photons do not have a purely
classical description. Get used to it.
It's many shadow partners in other worlds. World is a confusing
term unless we define it.
I agree. Frequently, many-worlders follow Deutsch and have a
schizophrenic attitude to "worlds" -- they are either any
component of any possible superposition, or the semi-classical
endpoint of the process of decoherence. In the first case,
"worlds", as components of a superposition, can interfere. In the
second case, worlds are effectively orthogonal and cannot
interfere. Equivocating between these meanings causes endless
confusion -- and idiot physics.
I always use the term "world" in the second sense, so worlds are
orthogonal and cannot interfere.
We might also say the system of the photon is in many states,
while the rest of the system (us, the screen) remain in one
state, until we interact with the many-state photon system. So
in that sense, you could argue the screen and us are in one
world until the decoherence. But the system of the photons
can't properly be described as any singe photon system.
Because the photon is a wave. The attempt to eliminate waves or
fields from physics in favour of a purely particle ontology
failed. Feynman was most disappointed by this, but if you think
you can do better than Feynman.........
"Newton thought that light was made up of particles--he called
them "corpuscles"--and he was right. We know that light is made
of particles because we can take a very sensitive instrument that
makes clicks when light shines on it, and if the light gets
dimmer, the clicks remain just as loud--there are just fewer of
them. [...] I want to emphasize that light comes in this
form--particles. It is very important to know that light behaves
like particles, especially for those of you who have to gone to
school, where you were probably told something about light
behaving like waves. I'm telling you the way it /does/
behave--like particles. You might say that it's just the
photomultiplier that detects light as particles, but no, every
instrument that has been designed to be sensitive enough to
detect weak light has always ended up discovering the same thing:
light is made of particles." -- Richard Feynman
Feynman was wrong when he wrote this. Even he eventually saw that
this was wrong -- it couldn't be made to work.
Do you have a source I could read on this?
The failure of the Wheeler-Feynman absorber theory was always a
disappointment to Feynman. I can't recall an exact source, but I think
more recent books on the history and interpretation of QT probably cover
the development of Feynman's thought.
The main argument against Feynman's "all is particles" idea is the
existence of Hawking and Unruh radiation. These are effects of quantum
fields in curved space-time, and there is no particle explanation. See
Wald: "Quantum Field Theory in Curved Spacetime", or his "General
Relativity". Or the book by Birrell and Davies.
Bruce
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