In 1992, Bennett proposed an alternative scheme for quantum key distribution that uses only two non-orthogonal states. In the “B92” protocol, Alice sends to Bob the states |0and |+ with equal...

In 1992, Bennett proposed an alternative scheme for quantum key distribution that uses only two non-orthogonal states. In the “B92” protocol, Alice sends to Bob the states |0and |+ with equal likelihood, and Bob randomly measures them using the X or Z bases. For some combinations (which ones?) of state and measurement, Bob can deduce Alice’s state. Rather than announcing his measurements, Bob announces which qubits had their states determined with certainty. Complete the description of the protocol, including an analysis of the difficulties Eve faces in eavesdropping. What percentage of the transmitted qubits are discarded? On which of our basic information results does B92 depend?