Rare earth ions that can act as quantum bits

https://phys.org/news/2021-01-scientists-discovery-paving-ultrafast-quantum.... Researchers of the Institute of Physics of the University of Tartu showed that microcrystals, synthesized on the basis of mixed optical fluoride crystal matrices doped with erbium, praseodymium and some other ions of rare earth elements, can work as qubits that enable ultrafast optical quantum computing.