Abstract

The quantum teleportation scheme as proposed by Bennett, Brassard, Crépeau, Jozsa, Peres, and Wootters [1] is illustrated in the Fig. 1. Alice receives particle 1 which represents the qubit state, i.e. the two-level state, 1|Ψ⟩1=α|0⟩1+β|1⟩1,where α and β are complex amplitudes satisfying |α|2 + |β|2 = 1. The two orthogonal basis states |0〉and |1〉 are, for example, the spin up and spin down states of a spin 1/2 particle or two orthogonal polarization states of a photon. Alice wishes to transfer the quantum state to Bob but she is not allowed to deliver the particle directly to him. According to the projection postulate of quantum mechanics we know that a quantum measurement performed by Alice on the particle will in general change the quantum state at hand without revealing all the necessary information from which Bob could reconstruct the original quantum state. So how can she provide Bob with the quantum state?