Quantum information teleported from light to matter

Researchers at the University of Copenhagen (Denmark) have reported successful teleportation between light and atoms. Quantum information was transferred from a weak laser pulse at the sender’s location (Alice) to a glass cell containing a vapor of spin-polarized cesium atoms in a magnetic field at the receiver’s location (Bob). The two unconnected locations were separated by about one meter, and collective spin states of the alkali atoms were essentially used to store quantum states communicated by photons in the light beam. Quantum entanglement between Alice’s and Bob’s locations was created by a strong pulse of light passing first through Bob’s location such that fluctuations in the polarized light became correlated with spin fluctuations in the atomic vapor. When the entangling pulse arrived at Alice’s location, a beamsplitter mixed it with the quantum information in the weak laser pulse that was awaiting teleportation. “Alice” then performed homodyne Bell-type measurements of the optical fields at the output ports of the beamsplitter. “Bob” was made aware of the measurement results via classical photocurrents and completed the teleportation by applying a weak magnetic-field pulse to the atoms and thus mapping the initial quantum state of the weak laser pulse onto the collective spin excitation of the atomic vapor. Contact Eugene Polzik at [email protected].