However, if you want real precision, you need something either better than a crystal or something that will correct for tiny errors ... discipline from the rubidium clock.

a chip-scale optical clock was also proposed and demonstrated with better frequency stability and accuracy, which is mainly based on two-photon transition of Rubidium atom ensemble. However, the ...

However, if you want real precision, you need something either better than a crystal or something that will correct for tiny errors ... discipline from the rubidium clock.