Figure 4
Teleportation. (a) Without loss of generality we suppose a two-qubit system of the state \(|{\phi }(\theta )\rangle =\,\cos \,\theta |00\rangle +\,\sin \,\theta |11\rangle \) is used for teleportation (Fig. 1f). The entanglement of \(|{\phi }(\theta )\rangle \) measured by concurrence C(θ) = |sin2θ| can be strictly revealed by α and β for the teleportation process. In particular, α exactly coincides with C. (b) Using the relation C ≥ 2F expt − 178, as \(C,\alpha \mathrm{ > 2}{F}_{C}-1\sim 0.366\) (yellow region), two such entangled pairs enable teleportation of entanglement of qubits39. Compared to the steerable weight for quantifying EPR steering that are maximum for all pure entangled states79, both α and β can provide the qualities of entanglement previously shared between the sender and receiver for teleportation.
