Einstein’s Boxes. In an interesting precursor to the EPR paradox, Einstein proposed the following gedanken experiment: Imagine a particle confined to a box (make it a one-dimensional infinite square well, if you like). It’s in the ground state, when an impenetrable partition is introduced, dividing the box into separate halves, B₁ and B₂, in such a way that the particle is equally likely to be found in either one. Now the two boxes are moved very far apart, and a measurement is made on B₁ to see if the particle is in that box. Suppose the answer is yes. Immediately we know that the particle will not be found in the (distant) box B₂.
(a) What would Einstein say about this?
(b) How does the Copenhagen interpretation account for it? What is the wave function in B₂, right after the measurement on B₁?