Lanthanide atoms on MgO(100)/Ag(100) as Candidate for Single-Atom-Qubits

Lanthanide atoms on surfaces are an exceptional platform for atomic-scale magnetic information storage [Science 352, 318 (2016)]. However, their potential as qubits is yet unexplored due to the limited number of experimental set-ups that can coherently drive the spins of single adatoms.

Here we propose a combined experimental and theoretical method to estimate the performance of surface-adsorbed lanthanide atoms for quantum coherent operations. We investigate Er and Tm on on MgO(100)/Ag(100) with x-ray absorption spectroscopy to address their magnetic and electronic properties and with scanning tunneling microscopy (STM) to identify their adsorption sites. With atomic multiplet calculations and density functional theory, we infer for both atoms a magnetic ground state that is suitable for quantum coherent operations.

We investigate whether these systems lend themselves to ESR-STM. By adapting the piezoelectric model of ESR-STM [Science Advances 6, eabc5511 (2020)] to the case of lanthanide atoms, we show that these systems should exhibit a detectable signal and that they have a higher Rabi rate compared to the systems studied up to date [S. Reale et al., submitted (2022)]. In addition to their suitable electron spin properties, these elements possess a non-trivial nuclear spin which can be exploited to perform two-qubit operations on a single atom or to store quantum states in the nuclear spin.