Exploring Photogenerated Molecular Quartet States as Spin Qubits and Qudits

Photogenerated molecular spin systems hold great promise for applications in quantum information science because they can be prepared in well-defined spin states at modest temperatures, they often exhibit long coherence times, and their properties can be tuned by chemical synthesis. Here, we investigate a molecular spin system composed of a 1,6,7,12-tetra(4-tert-butyl-phenoxy)perylene-3,4:9,10-bis(dicarboximide) (PDI) chromophore covalently linked to a stable nitroxide radical (TEMPO) by optical and electron paramagnetic resonance (EPR) techniques. Upon photoexcitation of the spin system, a quartet state is formed as confirmed by transient nutation experiments. This quartet state has spin polarization lifetimes longer than 0.1 ms and is characterized by relatively long coherence times of similar to 1.8 mu s even at 80 K. Rabi oscillation experiments reveal that more than 60 single-qubit logic operations can be performed with this system at 80 K. The large magnitude of the nitroxide N-14 hyperfine coupling in the quartet state of PDI-TEMPO is resolved in the transient EPR spectra and leads to a further splitting of the quartet state electron spin sublevels. We discuss the properties of this photogenerated multilevel system, comprising 12 electron-nuclear spin states, in the context of its viability as a qubit for applications in quantum information science.

Automated summary

The study investigates the potential of photogenerated molecular spin systems in quantum information science, demonstrating the formation of a quartet state with long spin polarization lifetimes and coherence times, as well as over 60 single-qubit logic operations that can be performed at 80 K. The large magnitude of the nitroxide N-14 hyperfine coupling and the further splitting of electron spin sublevels are also discussed in the context of the system's viability as a qubit for quantum information science applications containing 12 electron-nuclear spin states.