On 10/15/2018 11:21 AM, smitra wrote:
On 15-10-2018 12:40, [email protected] wrote:
On Sunday, October 14, 2018 at 5:08:42 PM UTC, smitra wrote:
On 14-10-2018 15:24, [email protected] wrote:
In a two state system, such as a qubit, what forces the
interpretation
that the system is in both states simultaneously before
measurement,
versus the interpretation that we just don't what state it's in
before
measurement? Is the latter interpretation equivalent to Einstein
Realism? And if so, is this the interpretation allegedly falsified
by
Bell experiments? AG
It is indeed inconsistent with QM itself as Bell has shown.
Experiments
have later demonstrated that the Bell inequalities are violated in
precisely the way predicted by QM. This then rules out local hidden
variables, therefore the information about the outcome of a
measurement
is not already present locally in the environment.
Saibal
What puzzles me is this; why would the Founders assume that a system
in a superposition is in all component states simultaneously --
contradicting the intuitive appeal of Einstein realism -- when that
assumption is not used in calculating probabilities (since the
component states are orthogonal)? AG
It may look like one can re-interpret QM as being consistent with
Einstein realism, but Bell disproved this (if you assume locality).
Note also what Bruce said about "simultaneously".
My own idea is that we need to think about how to interpret time
evolution, instead of making all this fuss about superpositions.
Without collapse, the time evolution of a system can be interpreted as
a simple change of basis. You still have access to the initial state,
at least in theory. But if the system collapses (in the MWI this is
then an effective collapse due to you getting entangled with the
system), you cannot access the initial state anymore (in practice, you
might not have been able to do that anyway).
This all suggests to me that we live in a multiverse where each moment
of time defines a different universe, memories of the past refer to
alternative universes. We need to keep in mind that in experiments we
can only ever directly measure the present state.
But what does 'the present state' mean? The present second? The
present milli-second? "Present" is not a relativistic concept.
If you dig up a bone of a dinosaur, what you are seeing is a result of
processes in your brain right now. These are then the result of
photons interacting with your eye and ultimately you can draw an
inference about life on Earth, say, 150 million years ago.
And you can draw an inference about a few tenths of a second ago. But
you can't draw and inference about now.
Brent
But an explanation for the presence of the bones is ultimately just
information compression, we can account for information in our
universe "today" in terms of information present in an alternative
"past" universe.
According to classical physics, information is conserved in a one to
one way between the past and present, and this allows for an
interpretation of time evolution that says that our universe is
evolving in time. in QM this naive interpretation breaks down,
information is not conserved after collapse when you consider only one
term of a superposition. But there is no problem if you just stick to
the view where each moment in time defines a universe. The idea that
all information present in one universe can be accounted for in terms
of a single past universe", is false.
Another aspect of this is how a particle can tunnel through a
potential barrier. Here there is no intermediary state where the
particle is in the "classically forbidden region". So, we have a final
state, an initial state, but no intermediary state. Clearly this fits
in much better with the idea that time evolution is not real, it just
allows you to account for information in some universe in terms of
information in other universes.
Saibal
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