Researchers store quantum-linked single photons for 180 microseconds

Researchers at ICFO stored single photons in a crystal-based quantum memory for up to 180 microseconds while retaining quantum correlations with a second photon suited to optical fiber. They report that as the longest storage time for this kind of memory, equivalent to a fiber-link distance of more than 30 kilometers. The team used radiofrequency pulses to reverse the loss of coordination among atoms holding the photon's state. Longer storage could help future quantum repeaters synchronize signals across network segments. The result is a laboratory demonstration in a crystal cooled to 3 kelvin, not a deployed network link.