In a quantum network, information is stored, processed, and transmitted from one device to another in the form of quantum states. The quantum nature of the network gives it certain advantages over classical networks, such as greater security.
One promising method for implementing a quantum network involves using both atoms and photons for their unique advantages. While atoms are useful as nodes (in the form of quantum memories and processors) due to their long storage times, photons are useful as links (on optical fibers) because they’re better at carrying quantum information over large distances.
However, using both atoms and photons requires that quantum states be converted between single atoms and single photons. This in turn requires a high degree of control over the emission and absorption processes in which single atoms act as senders and receivers of single photons. Because it’s difficult to achieve complete overlap between the atomic and photonic modes, photon-to-atom state transfer usually suffers from low fidelities of below 10%. This means that more than 90% of the time the state transfer is unsuccessful.
Read more at: Phys.org