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. 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. 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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