Quantum Teleportation Achieved Over Record Distances
Two teams of researchers have extended the reach of quantum teleportation to unprecedented lengths, roughly equivalent to the distance between New York City and Philadelphia. But donâ€™t expect teleportation stations to replace airports or train terminalsâ€”the teleportation scheme shifts only the quantum state of a single photon. And although part of the transfer happens instantaneously, the steps required to read out the teleported quantum state ensure that no information can be communicated faster than the speed of light.
Quantum teleportation relies on the phenomenon of entanglement, through which quantum particles share a fragile, invisible link across space. Two entangled photons, for instance, can have correlated, opposite polarization statesâ€”if one photon is vertically polarized, for instance, the other must be horizontally polarized. But, thanks to the intricacies of quantum mechanics, each photonâ€™s specific polarization remains undecided until one of them is measured. At that instant the other photonâ€™s polarization snaps into its opposing orientation, even if many kilometers have come between the entangled pair.