On 7/26/2025 12:04 PM, John Clark wrote:
On Sat, Jul 26, 2025 at 1:17 PM Alan Grayson <[email protected]>
wrote:
*>> If you make a measurement with a Stern–Gerlach
magnet and determine that an electron is spin up, that
is equivalent to saying the electron is in a
superposition of spin left PLUS spin right along the
orthogonal axis. And it would be the same for spin
down except that then, instead of being a
superposition of spin left _PLUS_ spin right, it would
be a superposition of spin left _MINUS_ spin right.*
/> What orientation of the axes are you using to get that
result? Please be explicit. AG /
*I'm not sure what you mean by that. Place a point at the
center of a Stern–Gerlach magnet and place another point
_randomly_ at _any point_ on the outside circumference, draw a
line between those two points in extended in both directions
to infinity, that is one axis, _arbitrarily_ call one
direction along that axis "up" and the other direction "down".
Now draw another line 90° from the first one, that is your
other axis, pick one direction along that axis at _random_ and
call it "left", and the other direction "right" *
/> I don't follow. Isn't UP / DN along the path taken by the
electrons when they exit the apparatus?/
*The direction you want to call UP/DN is entirely up to you, but
whatever axis you pick if an unmeasured electron enters a
Stern–Gerlach magnet**that is oriented along that axis *
If it's an unmeasured electron the the chance of UP or DN could be
anything. Maybe it's an UP electron from a source that only produces UP
electrons.
Brent
*then there's a 50% chance it will go up and a 50% chance it will go
down.*
*And if you now rotate the magnet by 90° and call one end of that new
axis left and the other end right and an unmeasured electron enters
the magnetthen there's a 50% chance it will go left and a 50% chance
it will go right, and you'd get exactly the same result if the
electron had not been unmeasured but instead had been measured to be
spin up. *
/> How is RT / LT defined? AG /
*Spin left is defined as the superposition of spin up _PLUS_ spin down.
Spin right is the superposition of spin up _MINUS_ spin down.*
*
*
*You might object that the minus sign makes no observable difference
because the probability is the square of the absolute value of the
quantum wave functionand a minus times a minus is a plus; and that's
true in some circumstances but not in others. If X interacts with Y
and then I measure the outcome it makes no difference, BUT if X
interacts with Y and then I do _NOT_ measure the result, but whatever
the result is if I let it interact withZ and _then_ measure it, then
it does make a difference. That's why engineers who make quantum
computers have to make sure that there's no way intermediate results
of the machine can be determined, because if there is it would destroy
the superposition and the computation. *
*
*
John K Clark See what's on my new list at Extropolis
<https://groups.google.com/g/extropolis>
otm
--
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 view this discussion visit
https://groups.google.com/d/msgid/everything-list/CAJPayv2cBpqR9bgw-rnMOvtj%2B_Km4%3DUusk%2Br1fXc4buYLzoK-A%40mail.gmail.com
<https://groups.google.com/d/msgid/everything-list/CAJPayv2cBpqR9bgw-rnMOvtj%2B_Km4%3DUusk%2Br1fXc4buYLzoK-A%40mail.gmail.com?utm_medium=email&utm_source=footer>.
--
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 view this discussion visit
https://groups.google.com/d/msgid/everything-list/fb9e2351-ec41-43b0-ad70-881fec4cd31e%40gmail.com.
