Friday, February 27, 2015

Quantum Teleportation can Transfer two Properties With Fidelity

Suppose you see a beautiful table in a museum and you would like to have the same one at home. What could you do? One strategy is to accurately measure all its properties — its form (length, height and width) and its appearance (material and colour) — and then reproduce an identical copy for your living room. But this 'measure-and-reproduce' strategy would fail if the table were a quantum particle, such as a photon or an electron orbiting an atomic nucleus. The no-cloning theorem of quantum mechanics tells us that it is impossible to copy such a particle perfectly. On page 516 of this issue, Wang et al. show how to get around this apparent limitation of quantum physics. In a beautiful extension of previous experiments, they demonstrate how to transfer the values of two properties of a photon — the spin angular momentum (the direction of the photon's electric field, generally referred to as polarization) and the orbital angular momentum (which depends on the field distribution) — through quantum teleportation onto another photon.

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