On 1/27/2021 8:42 PM, Pierz Newton-John wrote:
On 28 Jan 2021, at 2:49 pm, 'Brent Meeker' via Everything List
<everything-list@googlegroups.com> wrote:
On 1/27/2021 5:11 PM, Pierz Newton-John wrote:
I’m not saying decoherence is reversible. I’ve corrected myself (or accepted your
correction) on that point. But my understanding of proposals for disconfirming MWI
involve extending quantum coherence to larger and larger scales. Deutsch has argued
that if we can get enough qubits into a quantum computation, we’ve effectively
“proved” MWI since “where did all that information come from?".
And Scott Aaronson has pointed out it all had to be in this world in order for
interference to produce an answer.
That argument rests on the definition of world as a decohered branch, and
Deutsch would not accept that definition.
Well, it's what everybody else means. If there's going to be
interference (and that's how quantum computer computes) then he must be
thinking that different components of a superposition count as different
worlds, e.g. when a |UP> sliver atom goes thru a horizontal SG then it
is in a superposition of |LEFT>+|RIGHT> and Deutsch wants to count those
as occurring in different worlds. But |UP> can be written as
superposition of left and right without the SG. It's just a choice of
basis.
Brent
I’m not sure if I agree with his argument, but I’m also not necessarily
convinced by that definition of “world”. I mean, it’s perfectly good as far as
it goes, but I’m not sure I’m happy with it being marshalled as an argument in
this way. If there is a world W which contains an electron in an up/down
superposition, then in the Deutsch picture, and I would say the Everett picture
in general, that means some observer in W is unaware of which world he/she is
in: the one where the electron is up or the one where it is down. Or rather
(and this is Deutsch not Everett), the stack of worlds where it is up or the
stack where it is down.The measurement leaks that information via decoherence,
and the worlds diverge irretrievably at that point.
Brent
Other proposals similarly involve reversibility at large scales. If QM is not
universal, then at some scale that will prove impossible not merely due to
technological limits, but limits of the laws of physics. If such a limit were
found, that would certainly disconfirm MWI.
--
You received this message because you are subscribed to a topic in the Google Groups
"Everything List" group.
To unsubscribe from this topic, visit
https://groups.google.com/d/topic/everything-list/xsl8cSDT4M8/unsubscribe.
To unsubscribe from this group and all its topics, send an email to
everything-list+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/167da069-d0ac-4dd5-aab4-4ece43eee3bf%40verizon.net.
--
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 everything-list+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/cbfa12b6-ad4b-6082-adc0-88a27436e16f%40verizon.net.
