Anisotropy and inhomogeneity of the magnetic properties of individual erbium ions in silicon

Long coherence times can be achieved by using the spin states of the rare earth ion erbium. These spin states are accessible with optical transitions, which provides possibilities for long range coupling of these states. We investigate the magnetic properties of single erbium ions in silicon in order to identify suitable ions for quantum communication. Our results show that the individual ions have highly anisotropic Zeeman splittings which vary from ion to ion. I will discuss the challenge this presents for identifying different site symmetries and creating a comprehensive model that describes the level structure of erbium in silicon.