Physicists Demonstrate a Four-Fold Quantum Memory

Researchers at the California Institute of Technology (Caltech) have demonstrated quantum entanglement for a quantum state stored in four spatially distinct atomic memories.

Their work, described in the November 18 issue of the journal Nature, also demonstrated a quantum interface between the atomic memories -- which represent something akin to a computer "hard drive" for entanglement -- and four beams of light, thereby enabling the four-fold entanglement to be distributed by photons across quantum networks. The research represents an important achievement in quantum information science by extending the coherent control of entanglement from two to multiple (four) spatially separated physical systems of matter and light.