Hi,
gamma and delta reporesent some combination of (alpha, beta)'s as you say. And for your question:
"If it is the first case, why would Eve measure both of the qubits, and why would we discuss the values that gamma and delta can take (they can take any values in [0, 2pi]? ) ?"
Well this is just one possible attack from Eve. But yes in general Eve could choose other angles in [0, 2\pi] and you are of course free to discuss a more general situation. In fact the basic result (checking the inequaality for the security test) is the same whatever angles Eve chooses.
Hope this clarifies. Best,
N.M
gamma and delta reporesent some combination of (alpha, beta)'s as you say. And for your question:
"If it is the first case, why would Eve measure both of the qubits, and why would we discuss the values that gamma and delta can take (they can take any values in [0, 2pi]? ) ?"
Well this is just one possible attack from Eve. But yes in general Eve could choose other angles in [0, 2\pi] and you are of course free to discuss a more general situation. In fact the basic result (checking the inequaality for the security test) is the same whatever angles Eve chooses.
Hope this clarifies. Best,
N.M