This question is about the BB84 QKD protocol. Alice is trying to

establish a secret key with Bob. Eve is trying to intercept that key.

(iii) Alice chooses (randomly) to use the Hadamard (X-basis)

basis to encode her second bit sent to Bob. She sends a 0

(zero), again, as her second bit. Eve guesses Alice's basis

incorrectly. What is Eve's measurement outcome? Give every

possible measurement outcome, with corresponding

probabilities.