A Room-Temperature Diradical-Based High-Spin Qubit

Organic luminescent diradicals have recently attracted more attention for their potential applications in quantum science. Here, we have investigated the spin dynamic properties of two solid-state Müller- and Chichibabin-type Kekulé diradicals featuring different distances between two radical centers. The continuous-wave EPR (cw-EPR) together with echo-detected field-swept spectrum (EDFS) prove the existence of a thermally accessible triplet state at room temperature, promising a potential candidate for quantum manipulation as a high-spin state. As expected, the Rabi frequency of triplet diradicals is about √2 times that of a doublet. Both molecules exhibited clear Rabi oscillation curves and long dephasing times (<i>T</i>_m) at room temperature, promising their potential for applications in quantum information processing. The intra- and interdiradical distance, temperature, and magnetic nucleus effects on polarization and dephasing time are investigated. The results show that all those parameters have an intensive impact on spin dynamics. This investigation reveals an inherent conflict between the requirement of long dephasing time and large-scaling of electron spins. Further efforts should focus on how to obtain diradicals without significantly reducing the dephasing time to face the room temperature quantum manipulations.