From: <[email protected] <mailto:[email protected]>>
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
I think the problem arises with thinking of a superposition as an
expression of a fact of the system being in all components of the
superposition simultaneously. This mistaken interpretation leads to the
Schrödinger cat paradox, which you have worried about for a while.
But this is a mistake. A superposition is just an expansion of a wave
function in some basis or the other -- the choice of basis is arbitrary,
so it makes no sense to think of this expansion as representing anything
that happens in "reality" (in Einstein's sense of "reality"). The state
is still the original state until decoherence kicks in and then, because
of einselection of a preferred basis, we can say that the separate
states are "real" -- namely orthogonal, so that one other other is
chosen. Until that time, the only state around is the original state, as
can be demonstrated by the possibility of recoherence, in which case you
recover just the initial state and nothing else.
So for Schrödinger's cat, for example, if you could recohere the system
after one hour, say, you would find the cat alive in the box and the
vial of cyanide unbroken with the radioactive atom undecayed -- exactly
as you set the system up. It is only because the cat and apparatus are
large warm classical objects that this recoherence is not possible FAPP.
To think of the cat at some intermediate time as being both dead and
alive is just a confusion -- it is at all times either one or the other.
Bruce
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
