OptoREMS · Optically Addressable Molecular Spins in Rare-Earth Complexes

Optically addressable spin qubits—electron spin defects that can be optically polarized and read out—have revolutionized quantum technologies in sensing and information processing. However, these first-generation solid-state qubits like nitrogen-vacancy centers in diamond are confined within bulky crystals, limiting proximity to target samples and applications. A new revolution is poised to occur by realizing such spin qubit within molecules, establishing scalable, chemically tunable quantum platforms. Rare-earth complexes should stand out due to their shielded 4fⁿ ground states conducive to long spin coherence, strong spin–orbit coupling effectively linking spin sublevels with optical transitions, and parity-allowed 4f–5d transitions facilitating optical pumping and readout. Yet, they remain largely unexplored, highlighting new opportunities for spin qubits. Here, we propose to pioneer a new class of molecular spin qubits by engineering spin-selective 4f-5d transitions in rare-earth complexes. Two-pronged approach will be adopted: engineer angular-momentum-preserving excited states in a highly symmetric crystal field and deliberately break molecular symmetry by introducing chiral ligands. This crystal field and symmetry modulation strategy will ultimately be validated through advanced optically detected magnetic resonance techniques, directly demonstrating optical addressability of these tailored rare-earth molecular platforms. This project will benefit from strong interdisciplinary synergy. The researcher will integrate her expertise in rare-earth coordination chemistry, magneto-optical effects, and ab initio calculations with the advanced experimental and theoretical capabilities of Quantum Technology Group at University of Rostock. This collaboration will effectively bridge molecular engineering and quantum technology, thereby enhancing European competitiveness in quantum technologies.