 Consider again Schrödinger’s realization that an entangled state could be used to steer a distant particle into one of a set of states, with a certain probability. In fact, this possibility of ‘remote steering’ is even more dramatic than Schrödinger demonstrated. Suppose Alice and Bob share an entangled pure state of the sort considered by Bell, say two photons in an entangled state of polarization, where Alice has in her possession one of the entangled photons, and Bob has the second paired photon. Suppose that Alice receives an additional photon in an unknown state of polarization \(\ket{u}\), where the notation ‘\(\ket{\ }\)’ denotes a quantum state. It is possible for Alice to perform an operation on the two photons in her possession that will transform Bob’s photon into one of four states, depending on the four possible (random) outcomes of Alice’s operation: either the state \(\ket{u}\), or a state that is related to \(\ket{u}\) in a definite way. Alice’s operation entangles the two photons in her possession, and disentangles Bob’s photon, steering it into a state \(\ket{u^*}\). After Alice communicates the outcome of her operation to Bob, Bob knows either that \(\ket{u^*}\) = \(\ket{u}\), or how to transform \(\ket{u^*}\) to \(\ket{u}\) by a local operation. This phenomenon is known as ‘quantum teleportation.’ After the teleportation procedure the state \(\ket{u}\) remains unknown to both Alice and Bob. 