Yakir Aharonov (who is next to impossible to understand due to his thick accent and voice qualities). haha. 28 minutes
"What is the effect of this nonlocal motion?...The idea is the following then...In the beginning I certainly don't know through which slit the particle is going
because I want to know the module momentum. Then I wait for the interference pattern
to happen
and after it happens I can check whether the particle was
coming from this side [slit] or coming from
that side [slit] by a future experiment."
"So if I'm able to describe the situation in the present
by two vectors: one coming from the future that will tell me
through which path
the particle went and one coming from the past
that tells me that the modular momentum is
definite. Then I can see, indeed, there's nonlocal phenomena
and not violating causality, because I said I know only from the future
through which path the particle went. This is the basic idea
and now I will try to describe it more mathematically."
An atom, with its finite rest mass, can be brought to rest and can thus have a simultaneous position and momentum, even though we will not be able to measure these values simultaneously using a von Neumann-type strong measurement.
However as we have seen above in section 6.3.3, this simultaneous momentum is the Bohm momentum, which is not an eigenvalue of the momentum operator in the state under consideration, but the weak value defined in equation (6.13).
This means that this momentum can be measured by making the appropriate weak measurement of the momentum operator.
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