Quantum sensing of lanthanide atoms on MgO/Ag(100)

In this work, we propose a single erbium (Er) atom on MgO surface as a potential atomic spin qubit. To characterize the magnetic moments of Er, we employ a hydrogenated titanium (Ti) atom as a quantum sensor. We build Ti-Er dimers with different separations and orientations and investigate their magnetic interactions using electron spin resonance in a scanning tunneling microscope (ESR-STM). From the ESR spectra measured from Ti in the dimers, we determine the magnetic interactions between Ti and Er and, thus, the magnetic moments of Er at different magnetic field directions. The magnetic interaction varies significantly depending on the magnetic field directions due to the large magnetic anisotropy of Er on MgO. We further discuss the potential structures for the coherent control and detection of erbium spins.