A Clock Transition in the Cr7Mn Molecular Nanomagnet

A viable qubit must have a long coherence time T-2. In molecular nanomagnets, T-2 is often limited at low temperatures by the presence of dipole and hyperfine interactions, which are often mitigated through sample dilution, chemical engineering and isotope substitution in synthesis. Atomic-clock transitions offer another route to reducing decoherence from environmental fields by reducing the effective susceptibility of the working transition to field fluctuations. The Cr7Mn molecular nanomagnet, a heterometallic ring, features a clock transition at zero field. Both continuous-wave and spin-echo electron-spin resonance experiments on Cr7Mn samples, diluted via co-crystallization, show evidence of the effects of the clock transition with a maximum T-2 similar to 390 ns at 1.8 K. We discuss improvements to the experiment that may increase T-2 further.