Alice and Bob share a state a|++⟩+b|−−⟩, where the first qubit is Alice's and the second qubit is Bob's. Alice measures her qubit in the standard basis and sends the measurement outcome to Bob. If Bob wants a|+⟩+b|−⟩, what gate does he apply to his qubit in the following two cases? Choose your answer from I,X,Z,H.

Question

When Alice's outcome was 0:
When Alice's outcome was 1:

Answer 1

Please show your work on your previous posts before you post any more.

Answer 2

I
X

Answer 3

I think the same, that in first case you don´t have to do anythin, and in the second case it´s a bit flip, but it is not correct, why? I think it´s because the sign basis used at the begining? So which could be the correct answer?

Answer 4

0 --I,H

Answer 5

what are the answers for 6th a and 6th b questions pls help me