Past exam of the mathematics course of the University of Cambridge / 2019 / ii / Paper 1 / 10D / b / Solution

Alice performs a projective Bell-basis measurement on her qubits $C$ and $A$. Outcome $(x,z)$ occurs with probability $1/4$ and leaves Bob's qubit inAlice sends the two classical bits $(x,z)$ to Bob. He applies the inverse Pauli operationrecovering $|\alpha ⟩$ exactly, up to an irrelevant global phase. This is quantum teleportation: only local operations and classical communication are used, while the shared Bell pair supplies the entanglement resource.