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You are misunderstanding the physics. Suppose A and B are two quantum entities that result from a collision. They are entangled and moving away from each other.
by jblow 13y ago
You are misunderstanding the physics. Suppose A and B are two quantum entities that result from a collision. They are entangled and moving away from each other. The math very clearly says that a modification of A's state will alter B's state after the time of collision. In fact, it must do so, since A and B do not have separate states. Their states are the same one little chunk of math.
This even works if the states are known! This is how quantum cryptography works. You put two particles into Bell state with each other, give one to someone else, and then decide later what message you want to send.
I recommend learning the math. It is pretty simple if you already have linear algebra.
- yk 13y agoWell, what I am saying is, that the state of two entangled photons (with polarization +,-) is s_e= a |+-> + b |-+> and not s_n= a |+-> + b |-+> + c |--> + d |++> as is the case for two arbitrary photons. ( See also my post script to the original post.)
- jblow 13y agoI don't know why you think that? a|+-> + b|-+> is a very special-case entanglement. Yes, you'll see that one mentioned in Wikipedia (and quantum cryptography and etc) because it's very simple. The general form for the states of two photons is exactly as you have listed for s_n. For some coefficient values of a, b, c, d, the photons are "entangled", for some, they are not "entangled". How do you know which is which? It is whether you can factor the polynomial into two separate expressions of the form (x|+> + y|->). If you can do this, the photons are not entangled; if you cannot do it, they are entangled. Since most sets of (a, b, c, d) represent unfactorable expressions, you would expect almost any expression chosen at random to represent an entangled pair. Clean un-entanglement is the rare exception.
- oisadiusahd 13y agoClean un-entanglement is the rare exception. This is true only for pure-state entanglement (which itself is a rare exception ;-).