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Quantum Wave Function and Collapse
Name: James
Status: other
Grade: 12+
Location: NC
Country: USA
Date: April 4, 2011
Question:
Does a quantum wave function actually physically collapse or is this purely mathematical? The double slit experiment leads me to believe the former. If so, where does the energy go?
Replies:
No, sir. The "area under the curve", the mass-energy of the particle, and any conserved quantum numbers:
when they disappear from one place, they always go somewhere else.
In the double-slit experiment, the electron-presence lost in the null zones is made up in the peak zones.
If you somehow arranged wave-function cancellation everywhere in the roughly forward direction,
that just means the electron was not allowed to go forward, and was probably reflected backward.
But in the slit experiment this deflection is just small amounts to the left and right, not 180 to the rear.
The only weirdness in it, is that a simple flat distribution modulated only by line-of-sight masking,
surprisingly flowers into ripply interference (something waves always do).
Combined distributions {flat }+{flat} = {high in some places, low in others, but the integral is preserved}.
Jim Swenson
James,
There are various interpretations. As I understand it, the energy does
not disappear. When an electron passes through both slits, it is not as
two electrons. When a wave functions consists of a distribution over
several states, it is possible for the same object to have both energy
levels at the same time. Every state conserves energy within its
version of reality. When a measurement is made, one of the possible
states is selected. The sequences of previous and future events that
agree with the selection are selected. There is no disappearing energy,
because previous events that require the unselected states have been
eliminated: they never happened.
Time is not absolute at the quantum level. What happens now can affect
what happened before now. Reality is not a sequence of events set in
stone. When not measured, and when not restricted by other
measurements, all possible realities exist. Each reality is consistent
within itself. When measured, each reality has a probability of
continuing. Those that do not agree with the measurement are removed.
When a second measurement is made, more realities are removed. Each
measurement will agree with at least one reality. The result of the
measurement depends on the probability of each reality. One is more
likely to see a result that agrees with a high probability reality, but
any existing reality has a chance of providing the result. These
realities are often called "timelines".
Dr. Ken Mellendorf
Your question is one that I think is still debated, but to my knowledge, is
not resolved by experts in the field. Quantum mechanics behaves differently
than classical mechanics, so we have to be very wary about transferring
classical concepts to quantum concepts. In the case of the double slit (or
other "double" experiments"). Even when the pairs are separated at distances
that exceed the speed of light x the distance, the particle pair seem to
know what its partner is "doing". Classically, that makes no sense. But we
are not dealing with classical processes.
Personally, I am not convinced by wave functions "collapsing" only when they
are observed. Particles do not think! You can write down wave functions
analytically for simple systems -- before and after -- and there is no
mathematical term that I can find dormant in the steady-state wave functions
that "collapses". This must mean that the wave function that we write is
only an approximation.
Vince Calder
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Update: June 2012
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