tthree said:
Mango I have a question for you. When I hit QM in college I performed well on the tests but didnt really think I understood the concepts like I usually do. I had to resort to memorization a robot like formula use. I feel this is not learning but rather performing. I switched to a mathematical based major after that.
You seem to project a higher understanding in this field. Now I cant remember the name of the particles involved but this is what my fuzzy memory recalls. The particle goes through the intense electromagnetic field near the nucleus of an atom. It splits into two particles with opposite spins. This is the interesting and confusing part. If a force acts on the spin of the one particle an equal but opposite effect is observed instantly in its partner particle even if the particle has traveled light years away and can't feel the force at all. It seemed to suggest a connection of all things in the universe independent of time and space. Are you familiar with this? If you are could you say whether this is speculation or fact. A little explanation might be nice.
I cannot guess from your description which particle or experiment you mean in detail. However from your described effect of two particles with opposite spin, which turns out to be opposite even after manipulation of only one of those particles - I guess you mean experiments on entanglement (i.e. a pair of photons).
Let me clarify the scenario. You have an experiment where the output are two photons. Both photons have opposite spin if you measure them. You can choose one of the photon, and make all kinds of experiments with it, it behaves like a normal photon. Now you make two experiments:
#1: You measure the spin of both photons. They are always opposite.
#2: You choose one photon, and manipulate it's spin reversibly (i.e. by rotating it). You then measure the spin of both photons. They are still opposite.
Now we come to the interpretation: The naive observer would think that the spin is opposite in the beginning (this is the outcome of #1), and since we rotate the spin of a single photon, and after rotation we compare it with the spin of the other photon (still being opposite as #2), the naive observer concludes that the rotation of the single photon must have instantly rotated the other photon as well.
Now the naive observer tries to prove his theory by direct experiment #3: He measures the spin of both photons (they are opposite as in #1), then he rotates the spin of one photon alone. In the final step he compares the spin of both photons again: They are now equal (not opposite)!
Obviously the naive theory of having two photons, which are connected by some instantaneous force, must be wrong.
But where is the flaw ? There are no two photons from the beginning. All there is is a single "Twophoton", which looks from either "side" as a normal photon, but when you rotate the Twophoton, both sides change simultaneous as it is the very same object. Once you measure the spin of this Twophoton (on either side), the Twophoton decays into two individual photons (with opposite spin).
Since this is a card forum, let me give an analogy. You have a complete single deck of cards, and you replace a single card with a joker. Then you shuffle the cards, and cut then in two piles. Obviously one of the piles will contain the joker. If you look through one pile and find the joker, you immediatly know that the other pile of cards doesn't contain the joker (as there is only 1 of them in the deck). You can even go to a remote location, look through the pile and "instantly" manipulate the other pile to contain a joker (or not).
At least for that part of the instant interaction, there clearly isn't something like a mystical force between both piles interacting over long ranges instantly. You would never say you had 2 piles of a half deck (2 photons). What you had was the half of a full deck (one side of a Twophoton).
This is as far as always measuring opposite spin. But what about manipulation of spin without measuring it ?
Say we did't replace a card with the joker before cutting the deck. We deal with an original deck, but a third party writes a hidden note that any specific card (i.e. the Seven of Spades) will be considered as the joker.
Now we can do the the experiment again, of course always find that only one pile will contain the joker (which is written on the hidden note).
After splitting the deck, you can even now manipulate the "jokerness" of your pile, by simply declaring that "all Spades on the cards should be considered as Hearts, all Hearts as Clubs etc." This you can do in the remote room also.
After you made the declaration, you may still hold the joker in your pile - or the joker will be in the other pile.
If you then look through the deck (and make the declared adjustments for the suits), and asking for the hidden note - you then will know if you have the joker in your pile or if the joker is in the other pile. Of course the jokerness of both piles will still be opposite.
For the observer it looks like you somehow instantly moved the joker from the remote room to the other pile (or vice versa). In fact you didn't.
Quantum mechanics is similar - which the "minor" detail that there is no hidden note which card the joker will be. You have a tool for measuring the jokerness of the pile you hold in your hand, and you have the ability to rotate the jokerness of your very pile (if you would know the joker note).
The observed results are the same as the photon experiments. The only difference - and that is fundamental - there is no hidden note).
