19.1-19.2

1. What was the most difficult part of the section? The quantum part. The unintuitive part. The bracket notation. All of the above. In seriousness though, the probabilities only allow them to detect an eavesdropper and not hide the information, correct? If so, is it possible (although something that can be made arbitrarily improbable) that Eve intercepts the key undetected? Since there is a 25% chance that Bob detects an error, the chance is 4/2^n for n bits that Eve is undetected (if I understand this correctly).

2. The polarization setup is interesting. The two-slit experiment is mind boggling. Quantum physics has leaked into our culture with things like Schroedinger's cat. What is it about the universe that allows something to be more than one way simultaneously unless observed? What is inherent in observation? Maybe it's that we have no way of observing something in more than one state, but I suppose if that were true, the two slit experiment wouldn't work. What the heck.