Understanding the Correlation of the Quantum Dephasing Time and Entangled Photon Interaction in Crystalline Tetracene Derivatives

Quantum-to-quantum transduction is the coherent exchange of information between quantum systems, which is an essential element of quantum information science (QIS). Molecular architectures provide unmatched flexibility for tailoring the properties that are critical to quantum transduction, and molecular synthesis affords the opportunity to build novel molecular materials from the bottom-up. Singlet fission (SF) in organic chromophore solids provides a potential means of executing photon-to-spin quantum transduction because absorption of a single photon results in formation of four entangled spins that constitute a triplet pair state (TT). We have demonstrated that SF in single crystals of 5,12-bis(tricyclohexylsilylethynyl)-tetracene (TCHS-tetracene) produces a long-lived quintet state ⁵(TT) that provides a promising new route to multiqubit systems for QIS. Here, we investigate the interaction of classical and entangled photons with TCHS-tetracene as well as the related TIPS-tetracene and tetracene to assess the molecular properties required for quantum transduction. From the classical two-photon absorption (TPA) experiment, we observed that TCHS-tetracene and TIPS-tetracene have a higher TPA cross-section than tetracene. The entangled TPA cross-sections of TCHS-tetracene and TIPS-tetracene (6.914 × 10^–19 and 5.057 × 10^–19 cm²/molecule, respectively) are about an order of magnitude larger than that of tetracene (5.146 × 10^–20 cm²/molecule), making TCHS-tetracene and TIPS-tetracene excellent candidates for demonstrating photon-to-spin transduction using SF. We also observed a longer coherence time for the TCHS-tetracene in comparison to the tetracene molecular systems investigated, which suggests its suitability for possible QIS applications.