QM, Bell's Inequality and Quantum Cryptosystems
"Easy, the particles are correlated at birth. *they* know what their orientation is, it is fixed at birth. The math says *we* don't know." No. Bell's inequality tells us that there are no "hidden variables". It's not that we don't know the value of the measureable prior to wavefunction collapse...the specific measureable doesn't exist prior to wavefunction collapse. When Bell formulated the testable inequality circa 1980, and then it was experimentally violated (the inequality, that is, not the theory behind it), it became accepted within physics that (as expected) wavefunction collapse determines (right then and there) the value of observables, forcing the universe to choose, according to the probabilities. (Of course, this was basically understood from QM's beginnings, but prior to John Bell's work we couldn't actually test that this was reality.) (I would argue that this was one of the necessary conceptual pieces needed for people to trust the notion of quantum cryptography.) Taking a measurement (whether acidentally or on purpose) forces the quantum system to "choose" instantaneously. Einstein understood this aspect of Quantum Mechanics so well that he and 'P' and 'R' concocted the EPR gedanken to show that this implies what is effectively "action at a distance"...the different pieces of a quantum system, even far removed, spontaneously 'know' about the other parts. (In fact, I would bet that Einstein's original complaints about QM's action-at-a-distance may have been what prompted the reactionary fad of 'well, QM is merely a useful calculational tool...) But in the end, as strange and unreasonable as this action-at-a-distance may be, it's now regularly seen in the laboratory. (Even wierder are the 'quantum eraser' and other bizarre behaviors). -TD
But in the end, as strange and unreasonable as this action-at-a-distance may be, it's now regularly seen in the laboratory. (Even wierder are the 'quantum eraser' and other bizarre behaviors).
Is there any practical way to translate this into doll-and-needles method of punishing modelled targets at a distance ? ===== end (of original message) Y-a*h*o-o (yes, they scan for this) spam follows: Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com
On Thu, 2 Jan 2003, Anonymous wrote:
No. Bell's inequality tells us that there are no "hidden variables". It's not that we don't know the value of the measureable prior to wavefunction collapse...the specific measureable doesn't exist prior to wavefunction collapse. When Bell formulated the testable inequality circa 1980, and then it was experimentally violated (the inequality, that is, not the theory behind it), it became accepted within physics that (as expected) wavefunction collapse determines (right then and there) the value of observables, forcing the universe to choose, according to the probabilities. (Of course, this was basically understood from QM's beginnings, but prior to John Bell's work we couldn't actually test that this was reality.)
This really gets into my interpretation. I don't need hidden variables. The crux to me is that the particles are correlated and we use math to describe the probability of what the correlation is. Once we measure one particle we know the other one. Before we measure we don't know anything. That's all. QM tells us what the probability distribution is for any given measurement, it can't tell us anything about a particular outcome.
Taking a measurement (whether acidentally or on purpose) forces the quantum system to "choose" instantaneously. Einstein understood this aspect of Quantum Mechanics so well that he and 'P' and 'R' concocted the EPR gedanken to show that this implies what is effectively "action at a distance"...the different pieces of a quantum system, even far removed, spontaneously 'know' about the other parts. (In fact, I would bet that Einstein's original complaints about QM's action-at-a-distance may have been what prompted the reactionary fad of 'well, QM is merely a useful calculational tool...)
In my model there is no instantaneous choice. It was chosen at the start. We can not know anything about the correlation until we measure, then we know everything.
But in the end, as strange and unreasonable as this action-at-a-distance may be, it's now regularly seen in the laboratory. (Even wierder are the 'quantum eraser' and other bizarre behaviors).
Yeah, Scientific American has some really nice "popular" descriptions of these things. It just doesn't seem weird to me. It seems like reality. :-) Patience, persistence, truth, Dr. mike
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