This entry briefly outlines the history and physics behind Entanglement. Note I said briefly, I mean it; so, I also provide various references at the end for further research.
Well, entanglement is probably one of the weirdest things in quantum physics that I have seen. It was discussed at length at the World Science Festival held at NYU this year. During a discussion on quantum reality and the interpretations of quantum mechanics, one of the scientists tried to explain this concept to us by means of the following example: Take a pair of gloves (labeled L and R for obvious reasons), then close your eyes and mix them up in a random fashion. Then, pick one glove at random and put it in a box and the other one in another box (with your eyes closed). Now, close both boxes and open your eyes. If I ask you what is in each box? You'll reply that each box has either L or R with equal probabilities. Thus, the state of the system is:
where 1/√2 is called the amplitude, whose square gives the probability associated with | L > or | R >. It is important to note that this is more than just a convention. But, one might argue that there is nothing "quantum" about this experiment. It is just plain classical probability with some extra notation. But, the idea of entanglement goes beyond classical physics. To illustrate this, one is directed to the paper of Einstein, Podolsky and Rosen which more or less says: Based on the existence of something as absurd as entanglement, one can say that the quantum theory is itself absurd. Then, a big debate issued over what exactly one means by "absurd"?, what is "reality"?, now what do you think you mean when you say something is "really absurd"? and all the other difficult questions which I cannot answer yet. Moreover, one must also note that the glove-example (that's how I'll refer to it in future posts as well if need be) is only an analog. It is well known that one cannot "picture" the quantum world using classical props. Thus, the said scientist was only trying to get the notion of entanglement into my brain as opposed to explaining what entanglement is. So, now the question arises: Can we then, hope to "understand" this concept? Of course! People have done it, people are doing it. All we need is a little background. So, I'll be learning it and in the process, posting whatever I learn here.
References: Of course, Wikipedia, SIDNEY LECTURE: QUANTUM MECHANICS IN YOUR FACE!, MIT lecture notes (this is better understood if the concept of state is clear I think), more to come later...
Posts
