High cooperativity coupling of nuclear spins in a Yb(trensal) molecular qudit to on-chip superconducting resonators*

In this work we study the coupling of Yb³⁺ nuclear spin states in a Yb(trensal) molecule to superconducting cavities. Experiments have been performed on magnetically diluted single crystals placed onto the inductor of lumped-element LC superconducting resonators with characteristic frequencies spanning the range of nuclear and electronic spin transitions. An external magnetic field is used to tune the spin transitions on resonance with the resonators. Results show strong coupling of cavity photons to electronic spin states and a high-cooperativity coupling in the case of nuclear spins. The nuclear spin-photon coupling is enhanced by the hyperfine interaction with the electronic spin. Attaining the coherent coupling regime is a requisite to perform non-demolition read-out of the electronic and nuclear spin states. This technology enables the implementation of quantum error correction in crystals of molecular spin qudits.