On 11/5/2019 9:21 AM, smitra wrote:
On 05-11-2019 02:53, Alan Grayson wrote:
IIUC, as the temperature rises, interference in the double slit C60
experiment declines, and eventually disappears. I don't think this is
really a which-way experiment because the interference disappears
whether or not which-way is observed. How does this effect the
collapse issue? Usually, IIUC, when interference ceases to exist, it
implies collapse of the wf. So, is the C60 double slit experiment
evidence for collapse of the wf? TIA, AG
Consider the C60 moving through one or the other slit and then ending
up at some spot x on the screen. If the state of the rest of the
universe when the C60 takes on slit is |A(x)> and it is |B(x)> if
another slit is taken, then the interference pattern locally at spot x
on the screen will be proportional to Re[<A(x)|B(x)>]. So, if there is
perfect which way information for C60 that arrive in the neighborhood
of spot x on the screen, then the two environmental states will be
orthogonal and the interference will vanish.
In case of the experiment in a thermal environment, the C60 will
suffer collisions with photons.
It's not collisions with photons from the environment. The C60s are
heated in the experiment, so it is IR emission from the C60 that puts
which-way information into the environment.
The states |A> and |B> will be different due to these collisions,
|A> and |B> are different ex hypothesi regardless of collisions or
emissions.
Brent
as in every such case the state the universe ends up in will depend on
which path the C60 took as the collision it suffered when it took one
path would not have happened (instead another collision event at the
another slit may have occurred). As the temperature rises, the
interference pattern will then fade away as the number of C60
molecules that passed through without interactions near the slits will
become small.
Saibal
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