(August 31, 2016 at 7:49 pm)bennyboy Wrote: Okay, if what you suspect is right, then that means you could, at least sometimes, infer whether a photon was acting as a particle or a wave from the resultant spread pattern.I'm not sure whether this absolute dichotomy particle/wave is really something that exists in quantum mechanics. From my understanding, even the "particle" mode is just a wave which is localized to a small space corresponding to the resolution of the measurement apparatus.
Quote:But I guess that's true anyway-- if you are engaged in an experiment, and I walk into the room after it's done, I assume I will be able to see a 2-stripe pattern, and say, "Aha! I know you were detecting activity at the slits!" If certain apparatus could also do this, then the results themselves might actually be useful.This should be illegal. Usually, in such cases, the (delayed) decision whether to measure or not does not change the possible outcomes in a way that would allow a conclusion about the decision. The typical example I can think of to illustrate what I mean is that of two entangled particles which are entangled to have opposite spin up or down, but the spin of each can be both. If they part until they are separated by a large distance, the receiver of one of them, Alice, can destroy the entanglement (at least from her point of view) by measuring its state. She will get up or down, and then knows for sure that Bob will see the opposite result. From Bob's point of view, there will always be fifty-fifty up or down, whether Alice looks or not. He can't tell *just from measuring his particle*, whether Alice has looked or not, whether the entanglement is still intact. The same kind of situation should generalize to all possible experiments, no matter how elaborate.
My problem is that if you could do this experiment at very long range, it seems you could actually send information at a speed faster than light. You could, for example, send a burst of photons from the moon, and then use their entanglement with the transmitting apparatus to set their state just before they arrive at a receptor. Isn't this "illegal"?
Quote:If you want to trip me out, show me a 4-state superposition (essentially a uniform distribution, right?), that only resolves itself to me when I look up my random symbols in a book.
I'll gladly oblige, but what do you mean by a four-state-superposition?
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
