a reply to: smithjustinb
So, you don't have to choose to measure anything. If there exists the ability for the information to be known, the wave will decohere. In a lab
setting, yes, I guess you probably have to choose to set up the detectors and set up the experiment, but the actual choosing to do that has little to
do with how decoherence occurs. Decoherence can happen independent of choice and independent of observation. Its not that you choose to observe. Its
that the path is able to be known. If any evidence gets left behind for any event that occurred, it means that the event took place in a defined
state. So, decoherence can happen independent of a conscious observer.
Like I said earlier, this is the misconception about decoherence and it stems from people trying to be independent of a conscious observer when QM
tells us consciousness plays a big role.
You said decoherence can happen independent of choice and observation but that's not in dispute. This is why I started the thread off talking about
the measuring problem. So the question is what is decoherence?
Let's say you have a particle in a state of pure superposition and the density matrix tells us there's a 64% chance you will find the particle in 1
state or a 36% chance you will find it in an 0 state. This means that diagonal elements have real components and off diagonal elements have imaginary
components. So the particle is in a state of coherence and the imaginary elements also give us interference.
When the system is coupled with it's environment, the imaginary elements go to zero. You now go from a pure state to a mixed state.
This is all decoherence tells you. It tells you why you don't see yourself sitting and standing in a chair at the same time. The imaginary elements
are gone and there's no interference but you still have probabilities.
This is where interpretation comes into play and you have a measurement problem. When a measurement occurs, the probabilities are gone and you find
the particle in a definite state.
Again, this is where interpretations come into play because if I choose to carry out a measurement and I observe the state that had a 64% chance of
being measured, what happened to the state that had a 36% chance of being measured?
MWI wants to avoid the measurement problem and say the 36% still exists but in a parallel universe. For some who support Copenhagen, the wave function
is statistical and it speaks to the uncertainty or lack of information of the observer, therefore the wave function collapses.
Decoherence has nothing to do with it. If it did there wouldn't be any need for these interpretations. When a measurement occurs something happens to
the evolution of the wave function. A definite state is observed and then the evolution of the wave function flows from that state. So you have the
deterministic evolution of the wave function, a measurement occurs and indeterminism takes over.
It goes back to my example about the potato chip rack. The observers choice creates reality on a macroscopic and a microscopic scale. When the
observer chooses to make a measurement and this could be buying a back of sour cream chips or measuring the spin of a particle, it alters the wave
function and a history flows from that choice.
This is why a non physical model of the wave function works out much better. It doesn't need parallel universes like MWI and it's not statistical like
Copenhagen. It says the wave function is a non physical reality that stores information about the probable states a particle can be in.
So this would be like our minds. We store information about probable states that can occur.
When you go buy that bag of chips, you have information about the probable state of buying a bag of sour cream chips or buying a bag of doritos. If
you knew the history of everytime you went into the store and bought chips you can say it's a 64% chance that you will buy sour cream chips and a 36%
chance that you will buy doritos. When you make that CHOICE, a measurement occurs and a history flows from that choice. This occurs on a macroscopic
and microscopic level.
So the wave function and the mind are the same thing. It's a non physical reality that stores information about probable states that can be measured.
edit on 8-5-2014 by neoholographic because: (no reason given)