Fast Photodriven Electron Spin Coherence Transfer: A Quantum Gate Based on a Spin Exchange J-Jump

摘要

Photoexcitation of the electron donor (D) within a linear, covalent donor-acceptor-acceptor molecule (D-A_1-A_2) in which A_1 = A_2 results in sub-nanosecond formation of a spin-coherent singlet radical ion pair state, ~1(D~(+·)-A_1~(-·)-A_2), for which the spin-spin exchange interaction is large: 2J = 79 ± 1 mT. Subsequent laser excitation of Ai_1~(-·) during the lifetime of ~1(D~(+·)-A_1~(-·)-A_2) rapidly produces ~1(D~(+·)-A_1~(-·)-A_2), which abruptly decreases 2/ 3600-fold. Subsequent coherent spin evolution mixes ~1(D~(+·)-A_1~(-·)-A_2) with ~3(D~(+·)-A_1~(-·)-A_2), resulting in mixed states which display transient spin-polarized EPR transitions characteristic of a spin-correlated radical ion pair. These photodriven /-jump experiments show that it is possible to use fast laser pulses to transfer electron spin coherence between organic radical ion pairs and observe the results using an essentially background-free timeresolved EPR experiment.