Multiple Quantum Coherences from Hyperfine Transitions in a Vanadium(IV) Complex

We report a vanadium complex in a nuclear-spin free ligand field that displays two key properties for an ideal candidate qubit system: long coherence times that persist at high temperature, T2 = 1.2 μs at 80 K, and the observation of quantum coherences from multiple transitions. The electron paramagnetic resonance (EPR) spectrum of the complex [V(C8S8)3](2-) displays multiple transitions arising from a manifold of states produced by the hyperfine coupling of the S = ½ electron spin and I = 7/2 nuclear spin. Transient nutation experiments reveal Rabi oscillations for multiple transitions. These observations suggest that each pair of hyperfine levels hosted within [V(C8S8)3](2-) are candidate qubits. The realization of multiple quantum coherences within a transition metal complex illustrates an emerging method of developing scalability and addressability in electron spin qubits. This study presents a rare molecular demonstration of multiple Rabi oscillations originating from separate transitions. These results extend observations of multiple quantum coherences from prior reports in solid-state compounds to the new realm of highly modifiable coordination compounds.