From: *Jason Resch* <[email protected] <mailto:[email protected]>>
On Mon, Jul 30, 2018 at 11:21 PM Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
On Mon, Jul 30, 2018 at 8:33 PM Bruce Kellett
<[email protected] <mailto:[email protected]>> wrote:
From: *Jason Resch* <[email protected]
<mailto:[email protected]>>
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.....
Waves/Photons, doesn't matter what you call them.
Within the quantum computer this wave/photon is simultaneously in
many different locations/doing many different things, performing
computations and doing useful work using all of its separate
superposed instances of itself. Once it's done doing all this
work it settles down on a final value which we can read. And it
will be correct, and may have finished an enormous computation in
a short period of time, if and only if, it did in fact split up
and do all these independent things simultaneously.
Or you can view the action of a quantum computer as a simple
interference effect. Incorrect solutions to the algorithm
destructively interfere. You don't have to introduce ideas such as
'being in different locations and doing different things.' It is
just simple interference in a wave. (And it is all in one world,
because interference can only occur within the one world.)
To add some clarity, I would say interference effects of a superposed
system can only be seen from the vantage point of another system which
has not interacted with that superposed/interfering system.
Hmmm! I'm not sure what you mean here. Certainly, the interference from
the two-slit set up is only observable when the photons interact with a
screen. I am not an expert in quantum computers, but I understand that
the output from the computation is generally read off from a set of
qubits that are separate from, but interact with the qubits that are
actually used for the computation. Is that what you mean? In general,
though, observing something means interacting with it.
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.
So do you accept or reject that this "wave" can be in different
places simultaneously?
A wave is not a localized object, so the same wave can extend to
different locations.
So then "a photon is not a localized object, so the same photon can
extend to different locations." -- is this right or wrong?
A photon is what causes a localized spot on a screen. A wave is what
interferes with itself. If you want to equivocate on the meanings of
words, you can say that a photon is extended. But I prefer to keep the
terms distinct, and apply them as appropriate in different contexts.
Bruce
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