English: Schematic of a quantum teleportation protocol. Before the actual teleportation, a pair of maximally entangled qubits in a Bell state is produced by source S and distributed between communicating parties A and B ("zeroth step"). The teleportation starts in step 1 when A subjects its part of Bell state together with state ${\displaystyle |\psi \rangle }$ to the quantum measurement in the Bell basis, obtaining 2 bits of classical information. In the second step, A sends to B a message consisting of these 2 bits. In the third step, B applies one out of four operations to its qubit, where the choice of the operation depends on the received classical message. The net effect is that B has at the end a qubit in state ${\displaystyle |\psi \rangle }$, as intended.