Abstract
The ability to design quantum systems that decouple from environmental noise sources is highly desirable for development of quantum technologies with optimal coherence. The chemical tunability of electronic states in magnetic molecules combined with advanced electron spin resonance techniques provides excellent opportunities to address this problem. Indeed, so-called clock transitions (CTs) have been shown to protect molecular spin qubits from magnetic noise, giving rise to significantly enhanced coherence. Here we conduct a spectroscopic and theoretical investigation of this physics, focusing on the role of the nuclear bath. Away from the CT, linear coupling to the nuclear degrees of freedom causes a modulation and decay of electronic coherence, as quantified via spin echo signals generated experimentally and in silico. Meanwhile, the effective electron-nuclear interaction vanishes upon approaching the CT, resulting in perfect decoupling and complete absence of quantum information leakage to the nuclear bath, providing opportunities to characterize other decoherence sources.
*The spectroscopic and theoretical work reported in this paper was supported by the Center for Molecular Magnetic Quantum Materials (M$^2$QM), an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0019330. Experimental work performed at the National High Magnetic Field Laboratory is supported in part by the National Science Foundation (under DMR-1644779) and the State of Florida. Synthesis of the HoW$_{10}$ sample was supported by: the EU (ERC-2018-AdG-788222 MOL-2D, the QUANTERA project SUMO, and FET-OPEN grant 862893 FATMOLS); the Spanish MCIU (grant CTQ2017-89993 and PGC2018-099568-B-I00 co-financed by FEDER, grant MAT2017-89528; the Unit of excellence ‘Maríade Maeztu’ CEX2019-000919-M); and the Generalitat Valenciana (Prometeo Program of Excellence).
